Climate risk assessment of the fisheries in Namibia

In Namibia, fisheries are important for food security and protein provisioning, income generation and trade; but they are vulnerable to the impacts of climate change. Not only does climate change impact the marine living resources crucial to fisheries; but changes in weather, currents and storminess are affecting the safety and effectiveness of fishing. Here we ask: What are the key risks from climate change to the eight large-scale fishery sectors of Namibia, and for the recreational and small-scale (artisanal) fisheries? For each fishery sector, we assessed three main risk components: (1) climate hazard exposure; (2) fish species sensitivity; and (3) socio-economic vulnerability. In combination, these three risk components are then used to calculate the overall climate risk for each fishery. Climate hazard exposure was assessed as highest for the small-scale, recreational, and rock lobster fisheries. Species sensitivities were highest for the rock lobster and crab fisheries, followed by monkfish trawlers, hake liners and hake trawlers. Socio-economic vulnerability was highest for the small pelagic fishery (linked to the collapse of pilchard). The overall climate risk


Introduction
Globally, climate change is impacting marine ecosystems through a plethora of effects, including rising sea temperatures, ocean acidification and reduced oxygen levels, as well as changes in ocean circulation, wind and rainfall patterns (IPCC 2022).These impacts are of global concern, due to their consequences for ecosystem services such as nutrient recycling, carbon sequestration, and food provisioning through fisheries (Davies and Riddell 2017).Fisheries, in particular, are vulnerable to the impacts of climate change, which may have profound effects on the abundance, distributions and sizes of fish (Poloczanska et al. 2013).Moreover, changes in storminess, sea level rise and flooding risks affect the safety and effectiveness of fishing and associated operations, out at sea as well as in the ports of landing (Sainsbury et al. 2018).Given the crucial role of fisheries for income generation, food security, and especially protein provisioning in many coastal communities, it is important to assess the risks that climate change poses to fisheries (Payne et al. 2021;Davies and Riddell 2017).
Namibia is among the countries where climate change is expected to have substantial impacts on the marine ecosystem and fisheries dependent on these (De Young et al. 2012;Iitembu et al. 2020;Warikandwa et al. 2023a), concerns that were expressed in the National Policy on Climate Change for Namibia (MEFT 2011).With Angola and western South Africa, Namibia borders the Benguela Current Large Marine Ecosystem (BCLME), which is characterised by a productive but above all highly variable marine environment (reviews: Hutchings et al. 2009;Jarre et al. 2015).Recent, climate-driven changes include warming sea temperatures in the north contrasting with some temperature decreases in the south (Lima and Wethey 2012) and changes in wind speed and direction, notably increasingly strong offshore winds during summer (Rouault et al. 2010).The most important perturbation in the Benguela ecosystem is the so-called Benguela Niño (De Young et al. 2012).Benguela Niños occur at irregular, roughly decadal intervals, when large-scale intrusions of warm, lowoxygen and nutrient-poor water from the north are observed (Koungue et al. 2019).These, on top of climate-driven changes have had various impacts on key stocks supporting Namibia's large-scale fisheries (De Young et al. 2012) and have also affected coastal fish populations, which are relevant to the country's recreational and small-scale fisheries (Potts et al. 2015).All sectors are affected by changes in weather patterns, storminess and sea level rise (De Young et al. 2012).
Fisheries are of considerable importance to Namibia, with total landings amounting to 385,161 tonnes in 2021 (FAO 2022); the sector's direct contribution to Namibia's GDP since 2015 was between 2.5 and 2.9% annually (NSA 2023).Namibia has a higher gross national income (GNI) per capita (US$ 4880 in 2022) than most other African countries except South Africa (World Bank 2023).This masks, however, that the country has some of the highest inequality levels in the world with regards to income distribution, standard of living and quality of life, with a Gini coefficient (describing income inequality) of 59% in 2018 and the wealthiest 10% of households controlling over half of the country's total income, whereas the poorest 10% only share 1% (Human Development Vol.: (0123456789) Reports, https:// hdr.undp.org/).Kainge et al. (2020) highlighted that perhaps contributing to this inequality, is that the marine fisheries are nearly exclusively large-scale, due to the harsh and arid coastal environment which prevented the formation of local or indigenous human settlements along the coast to be able to develop a culture of artisanal fishing.Moreover, access is currently restricted over large portions of the entire coastline due to national park protection or diamond mining concessions (Kainge et al. 2020).Even so, small-scale (artisanal) fisheries do exist along specific stretches of the coast, although these are poorly represented in terms of governance and legal rights, and have only recently received increased policy and scientific attention.These fishing communities can be considered as highly marginalised (MFMR 2021a; Warikandwa et al. 2023b).
Namibia's large-scale fisheries are based in only two landing ports-Walvis Bay and Lüderitz-and they consist of eight sectors that are very distinct in terms of target species, gears used, distribution of effort at sea, and total fleet sizes (MFMR 2018; and see Table 1 for an overview).Overall, they are a source of considerable employment for Namibians, and in 2020 there were 16,970 employees.Among these, 8845 were males and 8125 females, the former divided about equally across onshore and offshore jobs and the latter mostly employed in onshore processing facilities (MFMR 2020).It has been estimated that per-capita fish consumption in Namibia is around 12.5 kg per year, and that about 16.7% of the animal protein intake of the population is derived from fish and fish products (FAO 2021).Namibia is a net exporter of fish products, with US$ 711.4 million worth of fish products exported in 2019 (FAO 2021).Fisheries in Namibia are thus important for commerce, income generation and trade, as well as for food security and protein provisioning.
The recreational sector is an important and growing component of fisheries in Namibia; the country is a well-regarded destination for shore-based (or small boat-based) marine recreational anglers.Each year, large numbers of local and international tourists flock to the relatively short stretches of coastline accessible to angling, which comprise less than a quarter of the total coastline (~ 260 km of the ~ 1500 km long coast).This is contributing significantly to the coastal economy through the generation of revenue, employment and livelihood support, primarily associated with the tourism industry (Kirchner et al. 2000;Boyer and Hampton 2001;Khan 2023).However, with recreational fishing occurring year-round over a limited stretch of coast and with high numbers of anglers, concern has been raised with regard to over-exploitation at the sites open to the public (Barnes and Alberts 2008).Added to this are the climate change effects that are impacting several coastal fish species (Potts et al. 2015); for example, a popular species, silver kob Argyrosomus inodorus, may be contracting its range and is now hybridising with a related, warmerwater species that is incoming from the north, dusky kob Argyrosomus coronus (Potts et al. 2014;Pringle et al. 2023;Jagger 2024).
With climatic changes taking place and predicted for the BCLME region for some time now (e.g.Jarre et al. 2015), an initial climate vulnerability assessment of fisheries in the area was carried out in 2011, during a FAO/Benguela Current Commission Workshop in Windhoek, Namibia, and published the following year (De Young et al. 2012).Based on a combination of literature synthesis and expert elicitation, the workshop participants identified vulnerabilities for the fisheries in Angola, Namibia and the west coast of South Africa; for Namibia, they identified the demersal trawlers, the rock lobster fishery and small pelagic fishery as those with highest risk (De Young et al. 2012).Well over a decade has passed since then, and more data and information have become available, while fisheries have either responded to climate change and variability, or have encountered challenges in doing so.The present study, therefore, provides an update and more complete analysis based on the climate risk assessment framework of the Intergovernmental Panel on Climate Change (IPCC, 2014).Specifically, this study aims to: (1) Assess climate hazard exposure, by characterising the main physical hazards of climate change potentially encountered by Namibian fisheries, and the extent to which the different fishery sectors are exposed to each; (2) Assess the sensitivities to climate change for fish and shellfish species targeted by Namibian fisheries, and in turn how sectors targeting different species will therefore differ in 'sector-level species sensitivity'; (3) Assess the socio-economic vulnerability by sector, associated with 'adaptive capacity' or a sec-  Some 1500 small-scale fishers (men and women) living in coastal areas of the main towns, who depend on fishing, shellfish collection, and processing and marketing of fish as a primary livelihood and income source.Here referring to the coastal smallscale fishery only (a much larger, freshwater small-scale fishery also exists along the large inland rivers)

Methods
The climate risk assessment methodology of the IPCC ( 2014) was adapted to the specific situation of Namibia with regards to fisheries composition and data availability.Climate risk was assessed for the eight main fishery sectors currently distinguished for Namibia's large-scale fisheries by the Ministry of Fisheries and Marine Resources (MFMR 2018(MFMR , 2021b)), as well as for the recreational and smallscale (artisanal) fishery sectors (acknowledging that data were more limited for especially the latter of these two sectors).For each of the ten fishery sectors, we assessed three main risk components (Fig. 1): (1) climate hazard exposure; (2) fish species sensitivity; and (3) socio-economic vulnerability.In combination, these three risk components are then used to calculate (4) the overall climate risk for each fishery.The assessment was based on literature review, data compiled from online and government sources, and expert elicitation.The latter could build on the expertise from across the team of 21 authors, which spanned marine biology, fisheries science, oceanography, economics, and the social and legal sciences.

Fisheries sectors
The eight main large-scale fishery sectors in Namibia are (see also We scored 'climate hazard exposure' by assessing the interaction between each fishery sector's spatial distribution of fishing effort, and the distributions of 8 key climate hazards within 12 geographic zones that together describe the Namibian EEZ (Fig. 2).These zones were defined as a combination of 3 'regions of impact' from North to South (19°-21°S, 21°-25°S, and 25°-31°S); and 4 'zones of impact' from West to East: namely, oceanic (deeper than 1000 m), slope (200-1000 m deep), (inner) shelf (100-200 m deep), and coastal (0-100 m deep).We then allocated the spatial distribution of fishing effort by each sector within each of the 12 zones.
Fishing effort distribution was mapped using information collated from the MARISMA Geo Data Portal hosted by the Benguela Current Convention (https:// geoda ta.bengu elacc.org/).These included shapefiles and metadata describing the effort distributions of the eight large-scale fisheries sectors, and the areas where recreational angling is permitted in Namibia; the original maps were created for the marine spatial planning process (MFMR 2021b).For the small-scale fisheries where data were limited, we complemented this with information from MFMR (2021a), Hilundwa et al. (2022), and expertise within the author group.From the maps, we then derived approximate allocations of effort distribution by sector to the 12 regions (Supplementary Table S1).
To describe the most important climate hazards that the various fisheries may be exposed to, the following eight 'component hazards' were assessed: (1) Benguela Niños: recurring intrusions of warm, low-oxygen and nutrient-poor water from the area off Angola, into especially the northern and central parts of the Namibian EEZ; leading to sudden, marked increases in water temperatures and lowering of oxygen levels (Koungue et al. 2019).Known to affect recruitment of key stocks such as shallow-water hake and sardine, to have caused mass mortalities in coastal zone organisms (Lutjeharms et al. 2001;Potts et al. 2015), and possibly to have facilitated invasion of Angolan coastal fish species into Namibian waters (Potts et al 2014).Seen as the most important perturbation in the northern Benguela, with major recent events in 1995 and 2011, and an event mainly impacting Angolan waters in 2019 (Gammelsrød et al. 1998;Koungue et al. 2019;2021).(2) General temperature rise: Warming rates are very high (up to ~ 0.4 °C per decade) north of the  There is evidence of an increase in upwelling favourable winds (Rouault et al. 2010), linked to a greater heating rate over land relative to the ocean, resulting in an increase in intensity of upwelling (Bakun et al. 2010).Increases in strong offshore winds are relevant along the entire coast and will particularly affect coastal activities, such as tourism, recreational and rock lobster fisheries.(5) Low oxygen levels in water (hypoxia): In the central region, hypoxic conditions occur at different intensities during late austral summer due to the supply of low-oxygen waters from the Angola dome driven by physical processes and the biogeochemical demand linked to locally-driven decay of organic matter (Monteiro et al. 2006(Monteiro et al. , 2008;;Pitcher et al. 2021).In the vicinity of Lüderitz, upwelled water is generally oxygen rich, nevertheless local hypoxic conditions attributed to dinoflagellate blooms can lead to low oxygen waters.( 6) Sea level rise (SLR) and storm surges: Sea level rise along the Namibian coast was estimated at 1.87 mm per year (Mather et al. 2009).Models suggest no immediate risks, but this may impact on urban areas especially with increased wind causing flooding and storm surges; it could also lead to habitat loss for intertidal organisms and so have indirect impacts (Potts et al. 2015).( 7) Jellyfish blooms: Jellyfish have become far more abundant in the area than they were in the past, and the term 'jellyfish explosion' has been used (Heymans et al. 2004).This may not be primarily climate-related but instead linked to historical, decades-long overfishing of small pelagic fishes (sardine, anchovy), whose stock collapses may have led to an ecosystem regime shift (Lynam et al. 2006;Roux et al. 2013).Jellyfish blooms will particularly impact small pelagic fishes, due to predation of eggs and larvae and intense competition for food (Lynam et al. 2006;Flynn et al. 2012).( 8) Harmful algal blooms (HABs): There is some evidence of HABs affecting Namibian mariculture (Owoseb 2013).There are regular toxin tests, and exports are stopped if toxins are detected (and warnings against consumption of mussels in the affected areas are sent out by MFMR).HABs are expected to mainly impact coastal or inshore areas.
For each of the eight hazards, we scored the extent of impact in each of the 12 geographic zones defined above (see Fig. 1), based on available literature and expert elicitation.Impact-by-zone was scored between 0 (negligible impact) and 4 (very high impact; see Supplementary Table S2 for hazard impact scores across all 12 zones).We then assessed climate hazard exposure by fishery sector within each zone, by multiplying the scores for the individual hazards (ranging from 0 to 4) within each zone with the fishery's effort allocation (ranging from 0 to 1) within the same zone.For each hazard, exposure by fishery sector across the Namibian EEZ was then calculated as the sum of all per-region hazard exposure scores.Finally, for each fishery sector, overall hazard exposure was calculated, as the average of the 8 component hazard scores.
As noted above, two of the eight hazards-jellyfish blooms and HABs-may or may not be climate-related hazards.To assess the robustness of the analysis to include or exclude these two hazards, a leave-one-out analysis was performed (akin to Ortega-Cisnos et al. 2018;Ramos et al. 2022).This implied that overall hazard exposure was calculated for each fishery sector, based on their exposure to all hazards minus either jellyfish blooms, or HABs, or both these hazards.

Rev Fish Biol Fisheries
Vol.: (0123456789) Fish species sensitivity (S) Fish species may differ widely in their sensitivity to climate change (Hare et al. 2016), and there are differences in the species typically caught by Namibia's various fisheries sectors.This implies that at sector level, there will be differences in average species' sensitivity to climate change and hence associated climate risk.This assessment includes 30 fish and shellfish species that together comprise > 99.9% of Namibia's large-scale fisheries catches (based on data for 2015-2019; collated from FAO's FishStat database: FAO 2022).Moreover, it includes 8 further species that are of high importance to the recreational and small-scale fisheries.
To assess each species' sensitivity to climate change, information on their biological traits was compiled with special emphasis on traits linked to thermal preferences, specific habitat requirements, and resilience to fisheries and/or other disturbances.This approach closely followed that of Pinnegar et al. (2019), adapted from Hare et al. (2016).Systematic information was compiled for four biological traits; for each, a scoring system was then allocated from 1 (low sensitivity or high tolerance) to 4 (high sensitivity or low tolerance).The four traits included: (1) Tolerance of high temperatures.For each species, information on temperature preferences was taken from AquaMaps (accessed April-June 2022; Kaschner et al. 2016).To assess a species' tolerance of high temperatures, the 'maximum preferred temperature' (90th percentile of a species' full temperature range, TP90; Pinnegar et al. 2019) was used.A sensitivity score was allocated to each species, based on criteria for TP90 described in Table 2.
(2) Temperature specificity.To assess a species' robustness to variations in temperature conditions, the temperature specificity metric was used (Pinnegar et al. 2019).Species that are naturally limited to a narrower range of temperatures are considered more likely to be impacted than species that can thrive in a broader range of temperatures (Rijnsdorp et al. 2009).This may be particularly relevant in Namibia because of the combined impact of ocean warming and increased upwelling intensity, which will likely lead to increasing levels of thermal variability in the coastal zone.Temperature specificity was based on each species' range (T, in °C) of preferred temperatures (i.e.range between the 10th and 90th percentile temperature, TP10 and

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Vol:. ( 1234567890) TP90), and was scored based on the temperature specificity criteria described in Table 2. (3) Habitat specificity.This trait distinguishes between more mobile and widely distributed species that can thrive in a range of environments, and species that are less mobile and/or have specific, spatially restricted habitat requirements (e.g.reef-associated, more sessile species), considered more sensitive to climate change (Rijnsdorp et al. 2009) even if specific habitat requirements are mainly evident during some critical life stages (Petitgas et al. 2013).Information on habitat specificity of fish species was taken from FishBase, and in the case of invertebrates, from SeaLifeBase (accessed April-August 2022).This study follows the same criteria on habitat specificity as applied in Pinnegar et al. (2019).These are based on 'horizontal habitat,' ranging from coastal to oceanic; 'vertical habitat,' ranging from pelagic and epipelagic to demersal and benthodemersal (Engelhard et al. 2011); and 'mobility' ranging from highly migratory to sedentary (see Table 2 for criteria and scorings).( 4) Population resilience.Data was used from Fish-Base and SeaLifeBase (accessed April-June 2022) to determine a species' population resilience to exploitation and effects of a changing climate.Scores were allocated based on the estimated minimum amount of time needed for a particular population to double, the specific times of which are listed in Table 2.
Overall species sensitivity.For each species, an 'overall species sensitivity' score was then calculated.This was done by taking the average of the scores for high temperature tolerance, temperature sensitivity, habitat specificity, and population resilience.
Sector-level species sensitivity.For each of the fisheries sectors of Namibia, we then calculated the average, 'sector-level species sensitivity (S).'For the large-scale fisheries this was done by calculating, for each sector, the proportions (by value of landed weight) of the total catches comprised by each species.These were then multiplied with the overall sensitivity scores for each species, and all weighted species sensitivity scores summed to calculate the sector-level species sensitivity: For the recreational fisheries sector, catch composition data were based on number of fish caught (rather than value of landed weight; e.g.Kirchner and Beyer 1999), and only available for the 8 species principally caught: silver kob, West coast steenbras, galjoen, blacktail, barbel, and 3 elasmobranchs (spotted gully shark, smooth-hound, and bronze whaler shark).For the small-scale (artisanal) fisheries sector, no quantitative catch data were available; here, equal weighting was given to 4 species that together comprise the majority of small-scale fisheries catches (silver kob, West coast steenbras, blacktail, galjoen).

Socio-economic vulnerability (V)
With 'socio-economic vulnerability' (V) we refer to the ability (or lack thereof) that a community or fishery sector may have to anticipate and respond to climate-driven changes and to minimise, cope with, and recover from the consequences; this definition is in line with the IPCC Fifth Assessment Report (IPCC 2014).Our definition of V is akin to the reverse of 'adaptive capacity' (AC) as defined in the previous, Fourth Assessment Report (IPCC 2007), as the "ability of a system to adjust to climate change (including climate variability and extremes) in order to moderate potential damages, to take advantage of opportunities or to cope with the consequences."Socio-economic vulnerability is typically quantified based on socio-economic data linked with affluency and infrastructure (Biswas 2023).For this study, no (recent) socio-economic datasets were available that are directly comparable across all large-scale, small-scale, and recreational sectors (but see Stage and Kirchner 2010).Data were, however, available comparable across the eight fishery sectors comprising the large-scale fisheries.For these, four component metrics were generated, informative about socio-economic vulnerability.Data were collated from the Employment Verification Report (MFMR 2020), and complemented with data provided by MFMR (March 2023) and FAO (2022).The four metrics were scaled between 0 and 1 (lowest and highest vulnerability) to provide the following indices: For each sector, the overall 'socio-economic vulnerability' (V) was then calculated as the average of the four component indices.
For the recreational and small-scale fisheries, directly comparable quantitative information on these four metrics was not available; yet it seemed inappropriate to exclude these two sectors from the risk assessment.It is generally known that Namibian recreational fisheries generate high revenue and frequently involve both Namibians and tourists with high affluency; hence V was here tentatively assumed to be equal to the lower quartile of the vulnerability scores across the 8 large-scale sectors.By contrast, the small-scale fisheries sector is known to be highly socio-economically challenged; reflecting this, V was here tentatively assumed equal to the upper quartile of the other vulnerability scores.

Overall climate risk (R)
For each of the fisheries sectors, 'overall climate risk' (R) was calculated based on the three main risk components combined: (1) climate hazard exposure (H); (2) sectorlevel fish species sensitivity (S); and (3) socio-economic vulnerability (V).Note that different scoring systems were used for H (between 0 and 2), S (between 1 and 4) and V (between 0 and 1).In order to give equal weighting to each of the 3 main risk components when calculating R, these were each normalised across the sectors and scaled to range between 0 and 1, with higher values reflecting greater hazard exposure, species sensitivity, or socio-economic vulnerability respectively.The overall climate risk was then calculated as the unweighted mean of the standardised indices for H, S and V.

Stakeholder workshops
The key risks by sector that emerged from this assessment, were used to inform five stakeholder workshops held in September 2023, at locations across Namibia.Four workshops (in the coastal towns of Henties Bay, Swakopmund, Walvis Bay and Lüderitz) were attended by representatives of each fishery, and the final workshop (in Windhoek) by policy representatives.The communication of key climate risks to stakeholders was in line with Namibia's National Policy on Climate Change, which emphasises human rights values and acknowledges that climate change would disproportionately affect the rural poor, women, children, and marginalised groups (MEFT 2011).In the final workshop, one key representative was the Ombudsman of Namibia who in terms of article 91(c) of the 1990 Constitution of the Republic of Namibia has the "duty to investigate complaints concerning the overutilisation of living natural resources, the irrational exploitation of non-renewable resources, the degradation and destruction of ecosystems and failure to protect the beauty and character of Namibia."During all workshops, feedback on the outcomes of the risk assessment was sought from stakeholders, and their experiences with climate change; in particular, options for adaptation to climate change were discussed.The discussion of this paper includes a reflection on these workshops, including options explored to reduce risk and minimise consequences of climate change.

Spatial distributions of fishing by fishery sector
All sectors of the large-scale fisheries are characterised by distinct spatial distributions of fishing effort (Figs. 3 and 4).Four sectors are mostly active in the slope zone (200-1000 m depth) but over extensive latitudinal ranges (Fig. 3).These are the hake trawlers, hake liners, and monkfish trawlers, which all fish over the seafloor; and the midwater trawlers, which fish in the water column (targeting horse mackerel).
Vol:. ( 1234567890) The latter sector is absent from the southern area (south of 25°S).It should be noted that no trawling is allowed in waters shallower than 200m within the Namibian EEZ.The two pelagic fleets have very different spatial distributions.The liners targeting large pelagics (tunas, billfishes, sharks) have an oceanic distribution away from the continental shelf (Fig. 4a).By contrast, the small pelagic fishery (targeting mainly sardine, using purse seines) takes place over the shelf or in the coastal zone (generally where depths are < 200 m), mostly in the northern and central parts (Fig. 4b)-noting that sardine is currently under moratorium since 2018.Highly localised distributions characterise the two shellfish fisheries: with the deep-sea red crab fishery mostly confined to the slope zone (200-1000 m) of the north (Fig. 4c), and the rock lobster fishery to the south, immediately off the coast (Fig. 4d).The recreational fishery takes place along some specific stretches of coast between 20°S and 23°S, reflecting remoteness, and that much of the coastline is closed for recreational fishing (Fig. 5a).We acknowledge there is sporadic activity by small parties of anglers also in remote areas, organised as specialised tourist trips, mostly catch-and-release only, for which no data was available here.Namibia's small-scale fisheries are distributed broadly similarly to the recreational fisheries (reflecting similarities in gears and target species).They differ, however, in being more confined to the populated areas in the central zone; some small-scale fisheries also take place in the south, near Lüderitz (Fig. 5b).

Spatial distributions of climate hazards
Two of the 8 component hazards-Benguela Niños and general temperature rise-were assessed as particularly impactful in the northern (17°-21°S) and central (21°-25°S) zones with relatively high impact scores (mostly 1.5 and above; Supplementary Table S1); these zones lie closer to the Angola-Benguela front and more equatorward.These two hazards were assessed as relatively unimportant in the southern zones (where there is no evidence of rising temperatures).By contrast, ocean acidification and strong offshore winds were assessed as most impactful in the south, especially in the coastal and shelf zones (related with strong upwelling in this area).Jellyfish blooms were assessed as particularly relevant in the coastal, shelf and slope zones, but not in the oceanic zone.Two hazards-risk of low-oxygen water (associated with dinoflagellate blooms), and sea level rise (associated with increased risk of storm surges) -were assessed as only impactful in the central/southern coastal zones.Harmful algal blooms came out as of minor significance, only in the coastal zone of the central (more populated) zone (Supplementary Table S1).

Climate hazard exposure by sector
When climate hazard exposure was compared between the ten fishery sectors (Table 3), this was found to be greatest for the small-scale and recreational fisheries (Fig. 6; scores 1.81 and 1.80 respectively), higher than for all large-scale fisheries sectors.Among the latter, hazard exposure was highest for the rock lobster fishery (1.56).These three sectors have in common that their distribution is fully coastal or nearshore; hazard impacts are generally higher nearshore than offshore (Supplementary Table S2).For the recreational and small-scale fisheries, strong offshore winds and Benguela Niños came out as particularly important.For the rock lobster fishery, this was the case for ocean acidification, strong winds, and low-oxygen waters.The sector with fourth-highest overall hazard exposure was the small pelagic fishery (score 1.33; Fig. 6); here, the hazards assessed as most important were the Benguela Niños and strong winds, and risks of jellyfish blooms (Table 3).The other six sectors typically work further offshore, and were assessed as having lower overall hazard exposure (Table 3); this was lowest for the mid-water trawlers (score 0.19) and large pelagic liners (0.43).The hake trawlers and longliners (both scores 0.69), monkfish trawlers (0.72), and crab fishery (0.81) had intermediate hazard exposure scores.The Benguela Niños came out as most important single hazard in all six offshore sectors (Table 3).
The leave-one-out analysis performed to assess whether including or excluding two hazards that may or may not be linked to climate change-jellyfish blooms and HABs-revealed that there was no effect on the ranking of overall hazard exposure by fishery sector (Supplementary Table S3).

Temperature specificity
The temperature specificity (based on a species' range of preferred temperatures) was low (i.e.T range > 12 °C) in 8 species: smooth-hound shark, orange roughy Hoplostethus atlanticus, southern bluefin tuna Thunnus maccoyii, thresher and blue shark, black cardinalfish Epigonus telescopus and sardine (Fig. 7b, and Supplementary Table S4), indicating these species are fairly robust to temperature variations.Seventeen species showed medium temperature specificity (T range > 8 °C and < 12 °C), and for 10 species this was high (T range > 4 °C and < 8 °C).The narrowest temperature specificity (very high: T range < 4 °C) was found for West coast rock lobster, deep-sea red crab and West coast sole.All species with very high and most with high temperature specificity were either coastal species with fairly restricted ranges (such as West coast steenbras and rock lobster), or species inhabiting relatively stable deep-water habitats (e.g.West coast sole, deepsea red crab and both hake species).
Table 3 Climate hazard exposure scores for 10 sectors of Namibia's fisheries.The scores are based on each sector's effort distribution across 12 geographic zones (see Fig. 2) and the prevalence of 8 hazards across the same regions (scored from 0 to 4, indicating negligible to very high hazard levels).For each sector, overall hazard exposure is based on the average of the scores for the 8 hazards.

Habitat specificity
Eleven of the species assessed were oceanic, (epi) pelagic, highly migratory fishes, all with very wide distribution ranges, resulting in low overall habitat specificity (score 1; Table 4); these included sardine, various tuna and pelagic shark species, and billfishes (swordfish and blue marlin Makaira nigricans).Thirteen species belonged to the medium habitat specificity category (score 2), based on these being mobile but not wide-ranging oceanic species, and associated with the shelf, slope, or (open-water) coastal regions.The habitat specificity of 5 species was considered high (score 3), based on these being less mobile or Table 4 Habitat specificity traits for 38 key fish and shellfish species in Namibia.Overall habitat specificity is based on a combination of mobility, horizontal and vertical habitat prefer-ences, and defined as either 'low' (1), 'medium' (2), 'high' (3), or 'very high' (4) (see Table 2  Rev Fish Biol Fisheries Vol:. ( 1234567890) resident, reef-associated species (the 'recreational' species galjoen, blacktail seabream and bronze whaler shark) or mobile, bathydemersal species (shallow-and deep-water hake).Eight species considered sedentary or of low mobility were scored as having very high habitat specificity (score 4); these were either coastal (e.g.West coast rock lobster) or associated with shelf, slope or deep-sea (e.g.deep-sea red crab, monkfish (devil anglerfish), West coast sole; Table 4).

Population resilience
Only 2 of the 38 species assessed were classified as having high population resilience (with rapid reproductive rates, and hence minimum population doubling times estimated < 15 months; Supplementary Table S5); these were Angola flying squid and round sardinella.The majority of species had either a medium (n = 14) or low (n = 16) population resilience (with minimum population doubling times, respectively, of 1.4-4.4years, and 4.4-14 years).Six species were characterised by very low population resilience (minimum population doubling time > years); these included Cape dory Zeus capensis, three elasmobranchs-smooth-hound, bronze whaler and spotted gully shark-and two deep-water species that are very long-lived and slow-growing: orange roughy and black cardinalfish (Supplementary Table S5).

Overall species sensitivity
The overall species sensitivity to climate change (based on the averages tolerance, temperature specificity, habitat specificity and population resilience) ranged between 1.5 and 3.8 for the large-scale fisheries species, and between 2.3 and 3.0 for the recreational/small-scale fisheries species (Fig. 8a; note that the total, potential range is from 1 to 4).The species assessed as having highest sensitivity overall, were rock lobster and West Coast sole (both scoring 3.8), followed by deep-sea red crab and kingklip (score 3.5).The next-most sensitive were shallow-water hake and monkfish (both score 3.3), followed by deep-water hake, Panga seabream Pterogymnus laniarius and Cape gurnard Chelidonichthys capensis (score 3.0).It is worth noting that several of these most sensitive species are among the commercially most important ones for Namibia's large-scale fisheries, with the two hake species representing over 50% of the total commercial value of the catches.The lowest species sensitivities were recorded for blue and thresher shark, yellowfin, bigeye and skipjack tuna, and swordfish (score 1.5), followed by sardine, round sardinella, Angola flying squid and albacore tuna (score 1.8).Typically, these species have warm-water affinities, wide distribution ranges, and/ or high turnover rates.It should be acknowledged that their populations might still show great fluctuations and that other factors than climate change might impact these.
Among the recreational/small-scale fisheries species (yellow bars in Fig. 8a), those assessed as most sensitive overall were West coast steenbras and spotted gully shark (both score 3.0); these have low or very low population resilience and localised distribution ranges.On the other hand, the lowest sensitivities in this group were recorded for blacktail seabream and smooth-hound shark (both 2.3).The last species stands out by having the lowest temperature specificity of all 38 species assessed (T range 16.13 °C), related with a particularly wide overall latitudinal range (most eastern Atlantic shelf seas from Norway to Cape of Good Hope).

Sector-level species sensitivity
Sector-level species sensitivity (based on the catch compositions by fishery sector, and all species' climate sensitivities: Fig. 8b) was highest for the rock lobster fishery (score 3.75), and second-highest for the crab fishery (score 3.50); both these fisheries are highly dependent on a single species, each characterised by high climate sensitivity.Three fisheries were assessed as having very similar, also very high average species sensitivities-the monkfish trawlers, hake liners, and hake trawlers (all scores ~ 3.1).The main target species for these fleets all have high to very high individual species sensitivities (ranging from 3.0 to 3.8).The small pelagic fishery and large pelagic liners were assessed as having fairly low sector-level species sensitivities (small pelagic fishery 1.75, large pelagic liners 2.11), in line with various pelagic species having relatively low climate sensitivities.The midwater trawlers, which primarily catch Cape horse mackerel, were found to have intermediate sectorlevel species sensitivity (score 2.51).For the recreational and small-scale fisheries, the sector-level Vol.: (0123456789) species sensitivities were found here to be intermediate (scores 2.55 and 2.63) and highly similar owing to the similarities in catches.

Socio-economic vulnerability
Socio-economic vulnerability varied greatly between the different sectors, between 0.24 and 0.96 (potential range of scores 0 to 1; Fig. 9).We acknowledge that for the recreational and small-scale fisheries, our vulnerability scores (low and high respectively) should be seen as tentative only, owing to lack of socio-economic data directly comparable to the eight large-scale fisheries sectors.Among the latter, socioeconomic vulnerability was highest for the small pelagic fishery (score 0.96); this was due to the very low total value of small pelagics landings, and very low per-capita revenue generated during 2018-2020, as well as significant job losses (by −9% annually; Supplementary Table S6).Ranking second-highest in socio-economic vulnerability was the rock lobster fishery (score 0.92); this has likewise a low total landings value, fairly low value per employee, and seen employment losses (by −12% annually).Both these sectors have offered few permanent positions in recent years (Supplementary Table S6).
Conversely, the crab fishery showed the lowest socio-economic vulnerability (Fig. 9); while not a very large fishery in total landings, it has offered the highest landings value per-employee, the highest percentage of permanent jobs, and seen substantial growth in employment in recent years (by + 51%; Supplementary Table S6).The midwater trawlers scored second-lowest in socio-economic vulnerability; this large sector has grown in employment opportunity (by + 9% annually).Vulnerability was assessed intermediate for the other four sectors: due to job losses in the large pelagic liners (by -20% annually over 2018-2021); to a small proportion of permanent positions in the hake trawlers and hake liners; and only modest per-capita revenue generated in the hake trawlers, hake liners, and monkfish trawlers (Supplementary Table S6).

Overall climate risk
The rock lobster fishery emerged as the sector with highest overall climate risk, and the midwater trawlers as least at-risk (Fig. 10).This was due to the rock lobster fishery ranking high or highest for all three risk components: hazard exposure, species sensitivity and socio-economic vulnerability.The reverse was true for the midwater trawlers (Fig. 10).
The small-scale fishery ranked second-highest at-risk, although this assessment is provisional as socio-economic data directly comparable to the other sectors were lacking; this sector had the highest hazard exposure.Third-highest overall climate risk was recorded for the hake liners, which have fairly high socio-economic vulnerability and high species sensitivity of the target stocks.The small pelagic fishery ranked fourth-highest at risk; this was due to very high socio-economic vulnerability, and high hazard exposure.

Discussion
This study is the first holistic climate risk assessment for Namibian fisheries since 2011, when a workshop was held jointly by the three countries bordering the BCLME, and Angolan, Namibian and South African fisheries were jointly assessed (De Young et al. 2012).It confirms that Namibian fisheries are exposed to a range of climate change related risks.We found that some fishery sectors are particularly exposed to the physical environmental hazards-such as strong offshore winds and ocean acidification in the southern/ central coastal zones where the rock lobster, smallscale and recreational fisheries are most exposed, and high temperatures and Benguela Niños (in unpredictable years) impacting fisheries in the north.Other sectors have high species sensitivities to climate change-particularly the rock lobster, crab, monkfish and hake trawler and longline fisheries.Socio-economic vulnerability was of particular concern for the small pelagic, rock lobster and small-scale fisheries.Considered holistically, overall climate risk emerged as highest for the rock lobster and small-scale fisheries.Better awareness of key climate risks by sector can serve in identifying adaptation options that could reduce these risks and build climate resilience-a prerequisite already expressed in the National Policy on Climate Change for Namibia (MEFT 2011).No comparable data exist for the recreational and small-scale fisheries.For the recreational fishery, where participants are generally more affluent, V was assumed equal to the lower quartile of that in the other sectors; for the small-scale fishery, where socio-economic challenges are generally high, V was assumed equal to the upper quartile Vol.: (0123456789)

Sectors with highest climate risk
Rock lobster fishery.Overall the rock lobster fishery emerged as most 'at-risk' (in line with De Young et al. 2012).This was due to high scores for all three risk components-climate hazard exposure (including strong offshore winds, ocean acidification, lowoxygen water), species sensitivity, and socio-economic vulnerability (MFMR 2021b).Not only is the Namibian West coast rock lobster climate-sensitive due to highly specific temperature and habitat requirements (this assessment), but it is also vulnerable to low oxygen levels which can impair growth, lead to 'walkouts' and to mass mortalities (Beyers et al. 1994).Recently, Iitembu et al. (2021) carried out a climate vulnerability assessment specifically for this fishery (Iitembu et al. 2021); they also found it to be very vulnerable, as it is highly weather-dependent and operates in shallow inshore (0-30 m) areas.The authors reported that fishers have observed increases in both swell frequency and height, including concomitant bottom surge, making access to fishing gear challenging; and that costs of fishing have increased as more time is spent at sea for the same catch (Iitembu et al. 2021).These same concerns were expressed during our Lüderitz workshop by stakeholders associated with the rock lobster fishery.Added to this, stock declines have led to a reduction in the rock lobster quota (from 350 t recently, to 180 t for the 2022/2023 fishing season).Recommended adaptations include switching to other species such as snoek and hake, and importing lobsters for local processing-but government support is seen as necessary to facilitate this (Iitembu et al. 2021).
Small-scale fishery.The small-scale fishery presented as second-highest at-risk, although we acknowledge that if more socio-economic data would have been available, this ranking could have been different.This differed from the previous vulnerability analysis ( De Young et al. 2012), when it was assessed as 'medium vulnerability'.Most of Namibia's smallscale fishers are from marginalised communities with limited or restricted access to marine resources, in some cases displaced from direct access to the coastline such as the case of the Topnaar community (Kanyimba 2023).Their marginalisation is also partly due to poverty and exploitation by merchants and middlemen, who have control over credit and fish marketing (Warikandwa et al. 2023b); this drains away the surplus generated and has made many smallscale fishers indebted.Variability in catches and overcrowding at limited sites have reduced the income generated, which along with rising operational costs has made the economics of fishing uncertain (Warikandwa et al. 2023b).There is currently no recognised definition of the small-scale fisheries sector in Namibia's regulatory framework (Kanyimba and Jonas 2023).This has led to the contradictory situation where recreational permits are used, only allowing very limited sale of the catch; sale is only allowed if fishers are members of small-scale cooperatives or associations (e.g.Hanganeni Artisanal Fishing Association [HAFA] in Henties Bay: Sowman et al. 2021).There is, however, growing commitment in Namibia's Government to support small-scale fisheries, by promoting inclusion and securing livelihoods; the National Plan of Action for Small-Scale Fisheries (NPOA-SSF) has recently been published (MFMR 2021a).This is seen as a "significant milestone […] to move the small-scale fisheries sector from an under-estimated sector to one which recognises the rights of small-scale fisherwomen and men and the significance of their contribution to socio-economic development" (MFMR 2021a).The present study's findings emphasise the need for the new action plan for building climate resilience in this sector.

Sectors with medium climate risk
Small pelagic fishery (purse-seine).This sector stands out among those with intermediate levels of overall climate risk as its target stock, sardine, has collapsed; a specific Namibian national workshop on enhancing climate resilience in this sector was therefore held in 2019 (Iitembu et al. 2020).Sardine was historically abundant in Namibian waters, and the small pelagic fishery had its highest catches on record in 1968 when fleets from many different nations fished in the area; however, catches have been very low since the 1970s, and a moratorium has been in place since 2018 (Iitembu et al. 2020).Currently, Namibia's small pelagic sector is no longer sea-going and the processing sector-which still provides jobs in Walvis Bay-is fully reliant on imported sardine and (Namibia-fished) horse mackerel (Iitembu et al. 2020).Land-based employment is steadily decreasing (from 649 employees in 2018 to 475 in 2021: MFMR 2020b, and MFMR unpublished data).While overfishing is generally accepted as the primary cause of the decline historically, prey competition with now abundant jellyfish and gobies, also predating sardine eggs and larvae, may be preventing stock recovery (Lynam et al. 2006;Flynn et al. 2012).However, the stock is also exposed to low-oxygen waters and warm-water intrusions from the north, and the 1995 Benguela Niño, which followed a low-oxygen event in 1994 led to the lowest stock levels on record (Bartholomae and van der Plas 2007; Iitembu et al. 2020).This climate risk assessment confirmed the high exposure to these different environmental hazards (Table 3).Stakeholders also argued that high predation levels by fur seals and other predators may be hampering stock recovery (see also Iitembu et al. 2020).The sardine stock, however, has a rapid reproductive rate which implies a high potential for population recovery once fishing is reduced, provided that environmental conditions are right (reflected in low species sensitivity score in this study); in the cooler, Southern Benguela Upwelling System (South of Lüderitz and off South Africa), sardine did indeed bounce back (Hutchings et al. 2009).Though some stakeholders argued for the small pelagic fishery sector to be removed from this risk assessment, we have decided to retain it, even though it is so far no longer an active, sea-going fishery in Namibia.The latter does, however, mean that the value and robustness of the assessment to inform future potential adaptation measures may be more limited than for the other sectors.
Hake liners, hake trawlers, and monkfish trawlers.These three fisheries have similar, offshore spatial distributions (Fig. 3) resulting in similar, medium hazard exposure scores (0.69-0.72); their target species have high climate sensitivities: 3.3 and 3.0 for shallow-and deep-water hake, 3.3 for monkfish, and 3.8 for West Coast sole (main bycatch in the monkfish fishery).These high sensitivities are important, as hake in particular comprises Namibia's most commercially important marine living resource.High sensitivities might have contributed to the stocks' very slow trajectory towards recovery, after excessive fishing by international fleets was halted in 1990 (Paterson and Kainge 2014); MSC certification was only achieved by the Namibian hake trawl and longline fisheries in 2020 (MSC 2020;MARAM 2022).In line with this study, shallow-water hake was described as being more sensitive to environmental variations than deep-water hake (Wilhelm et al. 2015a), but the latter having more confined spawning areas (Wilhelm et al. 2015b;Strømme et al. 2016), in spite of the wide distribution of adults.The growth (and population dynamics) of deep-water hake is mainly driven by upwelling in the southern Benguela and if this is expected to decline, would become more exposed to fishing and other climate-driven impacts (Wilhelm et al. 2020).Stakeholders in our Lüderitz workshop noted that deep-water hake (with cooler-water affinities) is now being caught, on average, further south than before, and that this was not clearly the case for shallow-water hake; this was relevant as it is deepwater hake that is preferentially targeted.For monkfish, there is evidence of a recent distributional shift into deeper waters (Yemane et al. 2014;Erasmus 2021).
In the previous vulnerability analysis of Namibian fisheries (De Young et al. 2012), the hake trawl fishery came out as 'highly vulnerable', whereas Vol.: (0123456789) here it emerged as medium-risk; this might reflect improved stock status since then (Kathena 2019;e.g. reflected in MSC-certification) but also inclusion of more socio-economic data for this highly efficient fleet.Already at the time, the authors qualified their finding that "the highly-industrialised demersal trawl fisheries for hake and other species… appear on current evidence much less vulnerable" (De Young et al. 2012).Stakeholders in our Walvis Bay workshop argued that-in spite of various physical climate hazards such as rough winters, and distribution shifts-the fishery can still manage to fulfil quotas, owing to its high efficiency; in fact, they said there is little awareness of climate change impacts in this sector, among those who participate in it.In spite of the medium overall climate risk, we do recommend that due attention is given to potential climate change impacts, based on the enormous commercial value of the hakes for Namibia, the high species sensitivity, and with it being a transboundary stock shared between nations, which increases its vulnerability as a regional resource (in line with De Young et al. 2012).
Recreational fishery.The recreational fishery emerged as particularly exposed to physical climate hazards (generally higher and more concentrated closer to shore), in common with the rock lobster and small-scale fisheries (Table 3).During the stakeholder workshop in Henties Bay, recreational and small-scale fishers shared their perception that strong winds and gusts now disrupt their fishing more frequently than they used to (cf.Rouault et al. 2010).They also felt that many coastal fish are now distributed 'deeper' and hence further from shore, as a possible response to warming waters, making them harder to catch using rod and line.They were unsure, however, whether this was due to climate change or to other factors, such as local overfishing or habitats impacted close to shore.Some of the target species have high climate sensitivity, for example West coast steenbras (Fig. 8a), which is known to have declined in many locations; this was confirmed by the experiences shared with us by both recreational and smallscale fishers-steenbras being their main species of concern.Even though highly valued as a target species, few studies have been carried out on steenbras since early key studies (e.g.Holtzhausen and Kirchner 2001;Holtzhausen et al. 2001), although very recently, the species is receiving renewed research interest (e.g.Veii and Nghipangelwa 2023;Shikongo 2024).Other target species emerged as much less climate sensitive-blacktail (dassie) and smooth-hound shark.One of the most important inshore species in terms of catch, silver kob, has medium climate sensitivity, is sensitive to change in water temperature (Pringle et al. 2023;Jagger 2024) and is beginning to be impacted by the related, warmer-water species, dusky kob, coming in from the north and hybridising with silver kob (Potts et al. 2014).Dusky kob was not included in this risk assessment but further range expansion might warrant its inclusion in future assessments.
As highlighted before, the recreational sector generates considerable income for local communities; there is perception within the sector that there is vulnerability to climate change (see also Townhill et al. 2019).In particular, those who are reliant on the fishery (guides, guest house owners and employees, etc.) may have challenges to adapt (Khan 2023), especially at more remote locations such as Henties Bay, where few alternative opportunities are available (desert tours and non-consumptive marine tourism activities might be their only alternatives).A recent 'horizon scan survey' based on many interviews with Namibian anglers, scientists and other stakeholders, has helped identify a set of priority research themes to underpin a sustainable and prosperous marine recreational sector in Namibia (Gusha et al. 2024).One key recommendation relevant to building climate resilience, is the inclusion in decision-making of anglers' knowledge, who experience climate impacts at first hand, to supplement the science.This would provide an inclusive, bottom-up approach with angler buy-in towards sustainable management (Gusha et al. 2024).

Sectors with lower climate risk
Crab fishery.This fairly small fleet sector (6 vessels in 2021) emerged as third-lowest at-risk among the ten sectors of Namibia's fisheries (also ranked as 'low vulnerability' in De Young et al. 2012).This was despite the target species-deep-sea red crab Chaceon maritae-having high climate sensitivity (score 3.5).This stock is among those previously heavily exploited, but it has gradually built up since 1990, and has been managed sustainably for some decades now (MFMR 2018).High sensitivity relates to the cool-water preferences and narrow range of Rev Fish Biol Fisheries Vol:.( 1234567890) preferred temperatures (Fig. 7), combined with the northerly distribution where warm-water intrusion may have greater impact.Deep-sea red crab is also vulnerable, because the fishery catches almost exclusively one sex only (95% caught are males: Amupembe 2019), which is likely suboptimal for reproductive potential.This sensitivity, however, is offset by low climate exposure in the area where this fishery takes place, and low socio-economic vulnerability due to high profitability.Deep-sea red crab is highly valuable-and exports in particular have steadily increased, from US$ 1 million in 1998 to US$ 15 million in 2018 (Amupembe 2019).In Walvis Bay, one stakeholder reflected: "Crab is a small fishery but it is doing well economically."Indeed, economic data analysed here showed that this fishery, among the sectors, offered the highest landings value peremployee, highest percentage (98%) of permanent jobs, and most growth in employment in recent years (by + 51% over 2018-2021).A general weakness is that this fishery has received only limited research focus and development, and a potential threat is that further warming and acidification in northern Namibian waters may negatively impact the stock (Amupembe 2019).Given the knock-on effects this would have on the fishery, it is recommended that potential climate change impacts on deep-sea red crab receive further research attention.
Large pelagic liners.This sector had second-lowest overall climate risk, reflecting that many large pelagics such as tunas and billfishes have wide spatial distributions and can live in broad temperature ranges (Fig. 8), meaning they are less sensitive to climate change (Pinnegar et al. 2019)-although they can still shift their distributions (e.g.South Atlantic tunas: Townhill et al. 2021).This fishery, however, is highly mobile by its nature, with longer distances covered than in the other sectors, and fishing much further offshore (Fig. 4b).There was moderate socio-economic vulnerability, partly due to a considerable reduction in employment over 2018-2021; work in this sector is moreover seen as labour-intensive owing to the large size of the fish caught (De Young et al. 2012;MFMR 2020).These challenges are partly offset, though, by the relatively high landings value per-employee in this fishery (second-highest among the sectors, after the crab fishery; Supplementary Table S6).In future, possible climate-induced distribution shifts of tunas and billfishes, and changing seasonality of migrations might have implications for this fishery, in spite of its high mobility-especially given high fuel prices; the transboundary nature of the stocks adds challenges to its management.
Midwater trawlers.Emerging as lowest climate risk among Namibia's ten fisheries, was the midwater trawl fishery; this was in line with De Young et al.'s (2012) vulnerability assessment.Indeed, Cape horse mackerel is the largest fishery by volume of catches for Namibia (and second-largest by total value; MFMR 2018).Cape horse mackerel was here assessed as having medium climate sensitivity (score 2.5); earlier studies reported that eggs and larvae in Namibian waters were found over a wide range of environmental variables, suggesting that they are robust to changes in the environment (Kreiner et al. 2014).Over the years, horse mackerel in Namibian waters has generally maintained high abundance levels but with large year-to-year fluctuations (Uanivi 2018); stock assessments indicate that the current biomass is at a sustainable level, but has gone down considerably in recent years, so that the quota had to be reduced (from 330,000 t in 2020 to 290,000 t in 2023; MFMR unpublished).Stakeholders agreed about horse mackerel being a more resilient stock, but also expressed concern about the recent decline, which they said may have been due to illegal fishing for smaller horse mackerel in shallow waters (less than 200 m depth), which provide important nursery areas.

Strengths and limitations
This climate risk assessment was lacking complete datasets for some of the ten Namibian fisheries sectors that were assessed, leading to some limitations that require our findings to be interpreted with some caution.For example, we did not have access to 'raw' VMS (Vessel Monitoring Systems) data to describe fine-scale distribution of fishing effort, owing to the well-known confidentiality issues around individual vessels' fishing positions based on VMS (Lee et al. 2010).We could, however, assess effort distribution through the spatial data products provided by the MARISMA Geo Data Portal of the Benguela Current Convention (https:// maris ma-bclme.com/ geo-dataportal/).Once superimposed on the bathymetry of the Namibian EEZ (see our Figs.3, 4 and 5), these clearly demonstrate the close alignment of each sector's Vol.: (0123456789) effort distribution with the 12 'impact zones' distinguished here (and this is expected for some fleets where the management framework is partly based on depth zones: MFMR 2021b).
Neither could we access primary data on the distributions of several of the physical hazards across the zones, and their relative impacts in each; this was derived from an expert elicitation workshop that involved Namibian, South African and UK scientists, combined with literature review (e.g.Hoegh-Guldner and Bruno 2010; Rouault et al. 2010;Lima and Wethey 2012;Flynn et al. 2012;Potts et al. 2015;Koungue et al. 2019).There might be additional hazards, not included here; sulphur eruptions and/or coastal sulphur plumes may be increasing and can impact on fisheries-for example in one event in 1992/1993 linked with high mortality in juvenile hake (Ohde and Dadou 2018).In future, new information on this and other hazards might warrant adjustment of the impact scores provided here; based on current knowledge, they may provide a representative description of where Namibia's main marine climate hazards may have the greatest impact, and so expose the various fisheries sectors active in each zone.
Our descriptions of species' sensitivity to climate change were based on a set of biological traits that included temperature and habitat preferences, and population resilience (in line with Pinnegar et al. 2019;Townhill et al. 2023), but they did not include a metric describing the exploitation status of a stocke.g.whether under-or overexploited (e.g.Kathena et al. 2016;BCC 2017;Kathena 2019).This choice was based on the latter information only being available for a minority of the species (albeit those of greatest commercial significance), and not for the recreational and small-scale fisheries species.This may have led to species sensitivity being underestimated for one stock which has recently collapsedpilchard Sardinops sagax, which formed the prime target species of the small pelagic fishery, now in crisis (Iitembu et al. 2020).However, climate change may not be the primary cause of this stock's decline, which has been attributed to prolonged high exploitation in the past (Belhabib et al. 2015), as well as to increased abundance of jellyfish and gobies, which predate on eggs and larvae and compete with pilchard for food (Lynam et al. 2006).The latter may hamper stock recovery, in spite of significantly reduced fishing effort (Flynn et al. 2012).
A possible caveat was that equal weighting was given to the four biological traits that together comprised species sensitivity, and to the eight component hazards used to calculate overall hazard exposure.The question of whether or not to apply equal weighting when combining different components, has been frequently raised in climate risk or vulnerability assessments (Monnereau et al. 2017;Pinnegar et al. 2019).Some authors (e.g.Cinner et al. 2013) used an approach where indicators were weighted based on expert opinion, with some components assumed to affect overall vulnerability more than others.In contrast, Allison et al. (2009) looked at various weighting schemes and found that the resulting vulnerability ranking remained largely unchanged despite the different methodologies employed during construction.The approach used here to apply equal weighting, was in line with several recent climate vulnerability assessments (Allison et al. 2009;Pinnegar et al. 2019;Townhill et al. 2023), including within the BCLME (De Young et al. 2012;Iitembu et al. 2021).
A further caveat was that the study did not include a certainty analysis, as was done by Hare et al. (2016), Ramos et al. (2022) and Gianelli et al. (2023) to examine the consistency of sensitivity scores of fish species as assessed by different experts participating in the scoring, or based on inclusion or exclusion of different component metrics.The species sensitivity scores in this study were fully based on biological traits data (accessed through FishBase), rather than expert elicitation, but the latter was important for climate hazard scoring; here, a leave-one-out analysis revealed similar rankings of the various fishery sectors depending on inclusion or exclusion of specific component hazards (Supplementary Table S3).
Our assessment of socio-economic vulnerability suffered from a lack of economic data for the smallscale and recreational fisheries that were directly comparable to those used for the large-scale fisheries sectors (MFMR 2020).The approach used here-of assuming vulnerability being equal to the upper and lower quartiles of that in the other sectors-must be seen as very provisional.It is, however, without doubt that the Namibian small-scale fishery is highly challenged economically (MFMR 2021a).The reverse seems true for the recreational fishery which has many affluent participants, although there are also participants (around a quarter) earning less than N$ 50,000 annually (Khan 2023).The recreational Vol:.( 1234567890) sector contributes significantly to Namibia's coastal economy through generation of revenue (direct and indirect), employment, and livelihood support (Kirchner et al. 2000;Khan 2023); hence its vulnerability could be underestimated here.Despite data limitations, we considered it important to include these two sectors in this risk assessment.The small-scale fishery in particular has suffered from a lack of scientific attention and policy representation-and is only beginning to be recognised as a sector by itself, with its own definition, rights and needs, rather than as a fragment of the recreational sector (Warikandwa et al. 2023b).We recommend that appropriate socio-economic data are to be collected for this sector, so that future policy decisions concerning this sector will be evidence-based.

Conclusions
Stakeholders connected with the various fisheries of Namibia-when presented the outcomes of this climate change risk assessment in five interactive workshops-broadly agreed with the key climate risks identified, and the relative risk rankings by sector.This indicates that the climate risk assessment is generally robust; which is also supported by broad agreement with De Young et al.'s (2012) climate vulnerability assessment.All stakeholders confirmed they are experiencing changes in the fisheries resourcesdeepening, latitudinal shifts, decreases in some species, increases in others (in line with Potts et al. 2014;Yemane et al. 2014;Jarre et al. 2015).Such changes in the resources are reflected in the variability in species sensitivities documented in this study, as also described in various other studies (Pinnegar et al. 2019;Townhill et al. 2023).Fishers highlighted they are experiencing changing weather and current patterns (as described by climate hazard exposure in this study), with consequences for the safety and effectiveness of fishing.Some are particularly impacted by this, and especially the small-scale fishers raised concerns; other fisheries, such as the highly efficient hake trawlers, can still go out and manage to catch their quotas, regardless of changing weather patterns.This illustrates that some sectors are adapting well, but others are much less able to do so.The latter is often due to financial constraints, or other components of socio-economic vulnerability (e.g.Warikandwa et al. 2023b).
Fishers in Namibia have knowledge and understanding that needs to be included in decision making around the marine environment and its marine living resources (MFMR 2021a(MFMR , 2021b;;Gusha et al. 2024).In particular, fishers emphasised that many other human pressures than climate change and fishing are impacting marine systems, that need to be addressed (e.g.diamond mining, shipping, dredging, and currently planned green hydrogen production: Rogers and Li 2002;Pulfrich et al. 2003;Ruppel and Katoole 2023).Marine Spatial Planning is increasingly recognised as an effective tool to facilitate management of the marine and coastal environment, especially where multiple stakeholders have either common or competing interests (Zaucha and Kreiner 2021).The current Marine Spatial Plan for Namibia, or Central Marine Spatial Plan (CMSP) is a major leap forward (MFMR 2021b); however, it does not yet incorporate climate change considerations, a step that may be achieved with a future iteration.
In conclusion, fisheries in Namibia are exposed to a range of climate risks that are different according to the particular sector.The fishing industry as a whole, and individual fishers are experiencing impacts of climate change.These impacts warrant scientific research to be able to fully understand the consequences for fisheries productivity.Policy support is likely needed for some sectors (in particular small-scale and rock lobster fisheries) to adapt, and needs to be based on sound evidence of the relative risks.Awareness of the key climate risks by sector, as showcased by the present study building on earlier work (De Young et al. 2012;Iitembu et al. 2020) will help to adapt, reduce risks, and build climate resilience in Namibia's fisheries.This will ensure that Namibia's development trajectory is climate resilient and focused on sustainable livelihoods of the most vulnerable, as well as the socio-economic viability of all sectors generally (MEFT 2011).

Fig. 2
Fig. 2 The Namibian Exclusive Economic Zone (EEZ, encompassed by thick black line), and 12 zones delineated by thin dotted lines, used here to assess climate hazard exposure by fisheries sector.The 12 zones were defined based on latitude (Northern: 17-21°S; Central: 21-25°S; and Southern: 25-31°S) and in East-West direction, based on depth (Oceanic: > 1000m; Slope: 200-1000 m; Shelf: 100-200 m; Coastal: < 100 m) Total landed value index, based on the total value of the annual landings by sector(averaged over  2018-2020; in N$), as an indicator of the total income generated by the sector.(2)Per-capita revenue index, based on the total landings value divided by the number of employees in each sector (averaged over 2018-2020), as an indicator for the income generated on a per-person basis;(3) Percentage permanent positions index, which assesses the proportion of employees permanently employed in the sector (as opposed to seasonal, casual, or temporary employees); (4) Annual employment change index, which assesses annual change in employment in the sector (i.e., an increase or decrease in jobs, as % of the average over the period 2018-2021).

Fig. 3
Fig. 3 Spatial distribution of fishing effort by four sectors of Namibia's large-scale fisheries: a hake trawlers; b hake liners; c midwater trawlers; and d monkfish trawlers.Thick black line encompasses Namibian EEZ, and thin dotted lines indicate 12 zones defined based on depth (< 100 m, 100-200 m, 200-1000 m, and > 1000 m) and latitudinal regions (northern, central, and southern)

Fig. 4
Fig. 4 Spatial distribution of fishing effort by 4 sectors of Namibia's large-scale fisheries: a large pelagic liners; b small pelagic fishery; c (deep-sea red) crab fishery; and d rock lobster fishery.Thick black line encompasses Namibian EEZ, and thin dotted lines indicate 12 zones defined based on depth (< 100 m, 100-200 m, 200-1000 m, and > 1000 m) and latitudinal regions (northern, central, and southern)

Fig. 5
Fig. 5 Spatial distribution of fishing effort by a recreational fisheries and b smallscale fisheries.Thick black line encompasses Namibian EEZ, and thin dotted lines indicate 12 zones defined based on depth (< 100 m, 100-200 m, 200-1000 m, and > 1000 m) and latitudinal regions (northern, central, and southern)

Fig. 6 Fig. 7 a
Fig. 6 Climate hazard exposure (H) for the 8 large-scale fisheries sectors of Namibia (orange bars) and for the recreational and small-scale fisheries (yellow bars)

Fig. 8 a
Fig.8a Overall species climate sensitivity for 38 key fish and shellfish species for Namibia, here shown in order of importance for the large-scale fisheries (orange bars) and recreational/small-scale fisheries (yellow bars) in terms of total catches.Sensitivity scores are based on the average of: tolerance of high temperatures; temperature specificity; habitat specificity; and population resilience.b Sector-level fish species sensitivity for the 8 large-scale fisheries sectors (orange bars) and for the recreational and small-scale fisheries (yellow bars)

Fig. 9
Fig.9Socio-economic vulnerability (V) for the 8 large-scale fisheries sectors of Namibia (orange bars) and for the recreational and small-scale fisheries (yellow bars).For the largescale fisheries, this is based on the combination of: total landed value index; revenue-per-employee index; percentage permanent positions index; and annual employment growth index.

Fig
Fig. 10 Overall climate risk for the ten fisheries sectors of Namibia, based on the combination of (1) hazard exposure, (2) species sensitivity and (3) socioeconomic vulnerability scores

Table 1
Characterisations of the ten fisheries sectors defined here that together comprise the Namibian large-scale, recreational, and small-scale fisheries.Based on De Young Vol.: (0123456789)

barbel Galeichthys feliceps, spotted gully shark Triakis megalopterus, smooth-hound shark Muste- lus mustelus and bronze whaler shark Carcharhinus brachyurus (the last four as unwanted bycatch in the small-scale fishery).
Fig. 1 Schematic illustrating the three main risk components that together comprise overall climate risk: hazard exposure, species sensitivity, and socio-economic vulnerability

Table 2
Definitions of four species traits that, in combination, comprise overall species sensitivity.For each trait, four rankings were distinguished, with scores 1 to 4 representing low to high climate sensitivity.Overall species sensitivity was calculated as the average of the four trait scores -- for full details).Species relevant to recreational and/or small-scale fisheries are marked with *