The Ten Commandments of Successful Fishery Management of Wild Brown Trout Salmo trutta Populations in Salmonid Streams in the Bohemian Region (Czech Republic)

Abstract

The brown trout Salmo trutta is a fish species that is vulnerable to climate change and anthropogenic activities in its native range. The case studies of successful restoration of brown trout populations are rare. In this study, fishery managers who successfully restored brown trout populations are sharing their know-how and advice about their conservation strategy. Overall, twenty fishery managers were interviewed to give advice about their successful conservation practices of local brown trout populations. Using a qualitative analysis method, ten main recommendations were extracted: (1) assess the status of local brown trout populations, (2) form a union of fisheries managers and work together, (3) support the ability of the streams to retain water, (4) prevent artificial removal of water from the salmonid streams, (5) adjust the brown trout stocking strategy to individual streams, (6) set strict protection of native wild brown trout populations, (7) enforce angling bans and regulations, (8) support the rearing of brown trout in the aquaculture sector, (9) limit brown trout stocking to genetically native fish, and (10) stock smaller 0 + brown trout instead of large adult ones. In conclusion, the fishery managers agreed on the basic management steps that need to be made to conserve brown trout populations.

1. Introduction

The brown trout Salmo trutta is a stream-dwelling fish species that is particularly threatened by climate change and other anthropogenic activities in its native range [1,2,3]. Native brown trout populations mainly suffer from droughts that are induced by man-made alterations of streams. These alterations cover mainly stream channelling and straightening, removal of natural meanders and pools, and deforestation [1,2,3]. Other examples of artificial removal of water from the streams are the creation of artificial snow for ski slopes and removal of water for watering gardens and golf courses [1,2,3]. As a result, brown trout populations have been vanishing from streams in central Europe since the beginning of the 21st century [4]. This population decline calls for a strict protection of local native brown trout populations. Such protection measures should lead to brown trout population restoration.

Unfortunately, restoration of trout populations is easier said than done. Fishery managers and conservationists must take steps to prevent the decline of brown trout populations. Those steps consist mainly of fishing regulations and stream restorations [5,6,7]. There are some case studies of successful restorations of local native wild brown trout populations, but they are scarce [8,9]. However, in most cases, neither fishery managers nor nature conservationists were able to stop the plummet of local brown trout populations in their native range. This leads to a decline of their populations on a larger scale [4]. Therefore, the need for more examples of good practice of brown trout population restoration has arisen.

This study is trying to fill this knowledge gap by providing the good practices of brown trout restoration strategy in its native range in central Europe. In this study, fishery managers who successfully restored brown trout populations on their streams are sharing their know-how and advice about their fishery management strategy. Twenty fishery managers were interviewed to share their knowledge and, hopefully, to inspire other fishery managers to implement the suggested conservation practices. They were all asked the same question: what did you do to save the brown trout populations on the streams that you are managing? It was expected that each fishery manager would name the same (or similar) conservation practices that led to sustainable brown trout populations. The goal was to summarise the suggestions and to write them down for other fishery managers in central Europe to follow.

2. Materials and Methods

2.1. Study Area

The data for this study were collected through the whole Bohemian region, which covers overall 70% of the Czech Republic (52,065 km²). The Czech Republic is in central Europe. Over 3% of the Czech population engages in recreational fishing, which results in 250,000 anglers visiting the local streams approximately 1 million times per year (data from the year 2020) [7]. The numbers of anglers and fishing visits increased by 5% between the years 2000 and 2018 [10].

There are 82 streams in the study area, which are further separated into 198 individual fishing sites (stretches of streams) that are divided by a visible structure (a weir, a dam, or a bridge). Rivers wider than 5 m were excluded from this study. The total area of the fishing sites is 204 hectares of water surface. They are all smaller (0.2–10 ha of surface area, with a median value of 1.2 ha). The streams are located in the temperate zone. They belong either to the North Sea Basin, to the Black Sea Basin, or to the Baltic Sea Basin. The streams are located mostly in the lowlands (200–600 m above sea level), are 2–8 m wide (the median value is 3 m), have mesotrophic or eutrophic nutrient levels, and have a fish biomass of 150–300 kg per hectare. They are dominated by brown trout Salmo trutta and gudgeon Gobio gobio [11].

In total, 170,000 fish weighing 87 tons were harvested in the streams of the Bohemian region in the year 2020 [12]. This number is declining every year and fell by 10% over the years 2000–2018 [11]. Anglers mostly harvested salmonids, mainly rainbow trout Oncorhynchus mykiss (70% by biomass), brown trout Salmo trutta (10%), and European grayling Thymallus thymallus (2%). The remaining fish harvested consisted of common carp Cyprinus carpio (5%), followed by other cyprinids (bream Abramis brama, European chub, vimba bream Vimba vimba, roach, and bleak Alburnus alburnus—4% altogether) and predatory fishes (European catfish Silurus glanis, northern pike Esox lucius, perch Perca fluviatilis, and pikeperch Sander lucioperca—4% altogether). The remaining 27 harvestable species of fish formed 5% altogether [12]. Rainbow trout is stocked using the put-and-take fisheries management and so it dominates the streams over several weeks during the trout fishing season (April and May) before anglers catch most of them [7].

Recreational fishing in the study area is heavily regulated by the state. Many fish species that are targeted by anglers have bag and slot limits that prevent anglers from overfishing the fish populations. Brown trout has a minimum legal angling size of 25 cm TL (total length) and a closed season from 1 September to 16 April [7].

The state aquaculture sector focuses little on production of brown trout—it forms under 1% of Czech aquaculture production [7]. Instead, the traditional fish such as common carp, rainbow trout, or European catfish form over 80% of the aquaculture production [7]. The aquaculture provides larger fish (30 cm TL and larger) for food and smaller fish (1–20 cm TL) for stocking purposes. It is approximately 10 times cheaper to stock small 0 + brown trout instead of large adult ones, so the financial returns of stocking small fish are better [7].

Owners of small hydropower plants are obliged to keep the water level on the streams on a minimum of 50% of the full capacity of the stream [7].

2.2. Data Collection

Overall, 20 one-hour-long in-depth face-to-face interviews were conducted with 20 selected fisheries managers who manage salmonid streams with sustainable self-reproducing native wild brown trout populations. The fishery managers restock fish, check the reporting of fish yields and fishing visits, communicate with anglers, and ensure that the streams and rivers are not littered and polluted. They check for littering and pollution by visiting the fishing sites weekly and checking for litter, trash, or signs of pollution (foam, dead fish, and unnatural water colour). We contacted the managers by telephone in cooperation with the headquarters of the Czech Fishing Union. Five fishery managers refused to participate (allegedly for time reasons), so we contacted 25 fishery managers altogether to schedule 20 full interviews. Altogether, there are 478 fishery managers who manage self-sustainable salmonid streams in the Czech Republic. In addition, one interview was conducted with each of the following specialists: a state water manager, fish biologist, meteorologist, disaster prevention expert, a geography expert, a conservationist, an aquaculture expert, and a fisheries regulations expert. The interviewees were selected randomly from a list of experts in each field.

The anonymised interviews took place from January 2021 to January 2022 according to a preprepared scenario. The questions were drafted several times by a sociologist, anthropologist, and a fisheries expert. This should ensure their validity. The interviews always took place during work hours in the office of each of the fishery managers. The interviews were not recorded, but rather, the interviewer was taking notes in-hand. The interviewed fishery managers were asked to list all the important fishery management adjustments that they use to keep a sustainable native wild brown trout population in their streams. Then, they were asked to elaborate on each of these adjustments and to explain why it is important and how specifically it should be done. The questions for the interviews were prepared based on scientific literature that describes the management of streams with trout populations [1,2,4,5,6,7,9]. For more information, check the in-depth interview scenario in the Supplementary Materials (Table S1).

We also reviewed and analysed state and local policies that regulate management on small salmonid streams (fishing regulations, water regulations, species conservation laws, and aquaculture regulations). Specifically, we analysed the Act No. 99/2009 Coll. (Act on Fishery) that describes fishing regulations and aquaculture regulations, the Act No. 254/2001 Coll. (Act on Water) that describes water regulations, and the Act No. 144/1992 Coll. (Act on Protection of Nature and Landscape) that describes species conservation. We connected the expert knowledge to the policies to provide specific recommendations.

2.3. Data Analysis

The in-depth interviews were qualitatively analysed using the grounded theory and in compliance with previously published papers that also performed a qualitative analysis of in-depth interviews with fishery managers [13,14,15,16]. The answers of the interviewed persons were re-typed and qualitatively analysed using the software ATLAS (free version from Atlas.ti). The qualitative model was created using the inductive approach: (1) collect data, (2) code data, (3) organise data around concepts, (4) form categories of related concepts, (5) elaborate patterns and linkages between categories, and (6) develop a theoretical explanatory model [13,14,15,16]. The ideas, topics, and recommendations were extracted from the qualitative analyses of the interviews. Then, the recommendations that over 50% of the fishery managers agreed to be important for the management of sustainable brown trout populations were used. As a result, there were exactly ten main recommendations that at least 50% of the managers agreed on.

3. Results

Based on the information from the interviews with the twenty fisheries managers and eight other field experts, the most important recommendations were established regarding the fishery management of salmonid streams in central Europe. The recommendations should lead to more sustainable management of local native wild brown trout populations in their native ranges. Here is the list of ten important recommendations that summarises them and describes each one of them more thoroughly (arranged by topic for a better clarity).

3.1. Assess the Status of Local Brown Trout Populations

It is essential to know the true status of wild brown trout populations and their abilities to form healthy, self-sustainable, and self-reproducing populations. Smaller salmonid streams, especially, should be assessed because trout have the highest chance to form sustainable populations there. It is not enough to just extract information regarding brown trout yields from mandatory angling logbooks and treat it as the estimation of a CPUE (catch per unit of effort) and proxy value of brown trout population densities. It is because many anglers practice the catch-and-release angling strategy, and they release most of the caught brown trout back to water. Some anglers release even the brown trout that has reached the minimum legal angling size and could be taken home. It is essential to know which streams can hold brown trout populations and which cannot.

3.2. Form a Union of Fisheries Managers and Work Together

Fishery managers who manage streams with prospering and sustainable wild brown trout populations should form a union together. The goal is to share the know-how and create a strong state agency or institution that will have the authority to advise other fisheries managers on how to manage their streams to create suitable conditions for prospering wild brown trout populations. This could be done, for example, by the Ministry of Agriculture. This agency or institution (and its committee) should ideally gather fisheries managers from the whole country to make the decision process as representative and reliable as possible. This union should then host webinars and workshops for other fishery and aquaculture managers to share the know-how and good practices regarding trout-friendly fishery management.

3.3. Support the Ability of the Streams to Retain Water

The problem of the streams in central Europe is that they have been drying up frequently during warm summers over the last decade (years 2010–2020). It is partially because streams are often straightened and without natural meanderings. This results to quick floods during rains in spring and autumn and to long-lasting droughts during warm summers. Neither quick floods nor droughts are good for trout populations, and both weather extremes usually lead to a decline in brown trout populations. It is important to revitalise the straightened streams, e.g., to restore the natural meanders and pools that increase the water capacity of the streams. If the streams are returned to their natural morphological parameters, they will be able to retain more water and therefore support wild trout populations.

3.4. Prevent Artificial Removal of Water from the Salmonid Streams

The other problem of central European streams is the artificial removal of water. Unfortunately, central Europe does not have many natural lakes or larger rivers, so streams are often used as a source of water for various purposes. The most important cause of water removal is the need to keep small hydropower plants functional. Unfortunately, these plants are situated on streams with low water discharge, and redirecting the water flow from the streams usually cuts the water supply in half. That means lower water depth and slower flow, which usually leads to brown trout population decline. Other examples of artificial removal of water from the streams are the creation of artificial snow for ski slopes and removal of water for watering gardens and golf courses. All three listed activities must be regulated, and the regulations must be reliably enforced. The state authorities must keep regularly checking if the regulations are met and fine the users who break the rules. The regulations regarding water removal should be stricter, and more importantly, they should be enforced more effectively.

3.5. Adjust the Brown Trout Stocking Strategy to Individual Streams

The fishery managers should divide the salmonid streams into several categories based on the ecological and environmental suitability of the streams for brown trout populations. Then, they need to select the streams that can hold sustainable wild brown trout populations. The fish stocking strategy must then be adjusted to the newly established categories of the streams. The streams with sustainable self-reproducing wild brown trout populations should not be a target for fish stocking of any kind (not even of hatchery-reared brown trout). Fishing should be either banned or heavily restricted here. The streams should function as a source of brown trout fry for other streams that need to be stocked to maintain brown trout populations (the sink streams). The streams where the brown trout has a low chance to form a sustainable population can be a target for intensive stocking of hatchery-reared brown trout, rainbow trout, and brook trout. The fish stocking can also be advertised as fishing sites that are mainly stocked for the purpose of put-and-take angling.

3.6. Set Strict Protection of Native Wild Brown Trout Populations

The streams containing sustainable and self-reproducing wild brown trout populations need to be strictly protected. This covers mainly setting a management rule that bans fish stocking altogether. The fishing ban must be imbedded in the law of the state and must be effectively enforced by police or a similar authority. Anglers must be made aware of this law, and this policy must be communicated with them. Anglers have the responsibility to know the law, and any policy must be updated and communicated to the entire fishery management and production chain of wild brown trout. The species protection management also covers population monitoring of piscivorous birds and mammals (great cormorant, Eurasian otter, grey heron, American mink) and restrictions of water removal for the needs of people. In addition, any activities on the streams that could be potentially harmful to local trout populations (water removal, stream straightening, construction of nearby pollution sources) must be banned.

3.7. Enforce Angling Bans and Regulations

The need to protect wild brown trout on the streams is true for the protection from angling as well. First and foremost, fisheries managers either must ban angling altogether or set strict fishing regulations. These regulations should cover bag limits and slot limits for brown trout as well as limited daily fishing hours and a closed season for winter and spring when brown trout spawns. In addition, harmful techniques need to be banned. This rule covers mostly double-hooks, triple-hooks, and backward hooks. These regulations do not need to be enforced on streams without native wild brown trout populations, but they should be enforced on the streams that still hold such populations.

3.8. Support the Rearing of Brown Trout in the Aquaculture Sector

The aquaculture sector should focus a bit more on the production of brown trout instead of the traditional fish such as common carp, rainbow trout, or European catfish. This way, fishery managers will have enough brown trout for the purposes of stocking and bolstering the wild populations in the streams that cannot hold sustainable and self-reproducing trout populations. The aquaculture industry should start focusing more on the non-production part of their job. Instead of just producing fish for food, they should also produce fish for the purpose of bolstering wild fish populations. The non-production part should be supported and co-financed by the government, e.g., by aquaculture financial grants.

3.9. Limit Brown Trout Stocking to Genetically Native Fish

If there is an established native wild brown trout population in a stream, stocking hatchery-reared brown trout of different geographical and genetical origin should be banned there. This will prevent genetical erosion of the local wild brown trout gene pool, and it will conserve the pristine brown trout populations. Local brown trout populations should be genetically tested for genetical purity, and if there is a need to bolster these trout populations, it should be done by spawning genetically and geographically local trout only.

3.10. Stock Smaller 0 + Brown Trout Instead of Large Adult Ones

Intensive stocking of adult brown trout usually leads to high mortality rates due to both natural and human-induced reasons. Conversely, experiments with stocking of eggs or newly hatched fish showed good results—the survival rates of the stocked brown trout were similar to the native wild trout. The stocking of eggs and fry showed better return rates in terms of biomass of harvested fish. It is also cheaper to stock small 0 + brown trout instead of large adult ones, so the financial returns are also better. In addition, larger stocked brown trout tend to migrate downstream, while the stocked 0 + trout tend to stay in the stream where they were originally stocked.

4. Discussion

The fishery managers agreed on ten key conservation measures that led to successful brown trout conservation strategy on salmonid streams in central Europe. The measures mainly consisted of the assessment of brown trout populations, unified approach of all fishery managers together, restoration of salmonid streams, adjusted fish stocking strategy, angling regulations, and support of brown trout in aquaculture production. The measures will now be discussed.

Firstly, the fishery managers agreed on the need to assess local brown trout populations. This included the analysis of their genetic origin as well. The goal was to find if the populations are 100% local and not inbred with the commercially stocked brown trout from hatcheries. However, the fishery managers confessed that they cannot reliably assess the populations because they lack the proper equipment and resources to do so. Instead, they sampled a small number of trout (20 randomly selected fish) caught on 500 m of each stream, and they extrapolated the results on the entire stream (hundreds of fish on 10–15 km long streams). The populations could therefore be partially inbred because, as other studies found, pristine brown trout populations are quite rare in central Europe [17,18].

The second issue was that the fishery managers are not yet well organised. In the Czech Republic, all the fishery managers are united under the Czech Fishing Union, but the interviewed fishery managers said that this organisation is too wide and un-focused for their needs. They argued that it is difficult to connect with all the other fishery managers who also manage streams with brown trout populations. They said that the Czech Fishing Union is not supportive enough because it is focused on the financial profit of selling fishing permits rather than conservation of wild fish populations. The managers are working on the conservation measures in their free time and on their expenses. Since other countries often do not have a centralised body that unites all fishery managers, their organisation is going to be even more difficult in these countries [19].

The third issue was the poor ecological status of streams in central Europe. Fishery managers agreed that the streams often dry up during hot rainless summers due to channelling and straightening of the flow. They also claimed to have negative experience with owners of local hydropower plants who do not comply with the minimum water levels in the streams that are set by the legislative measures. The fishery managers claim that it is difficult to prove that the plant owners have broken the rules. During hot summers, if the water level in the stream falls below the minimum levels, the trout start dying due to low oxygen levels in the water. If this happens frequently, the fishery managers refuse to stock and protect resident brown trout because they are likely to perish in the summer anyway. Other studies confirmed their opinion that brown trout populations are vulnerable to droughts and lower water levels [20,21].

The fourth issue was fish stocking. The managers claimed that stocking of any fish that is not of local origin is bad for the brown trout populations. Especially harmful are other salmonids that compete for food (rainbow trout, brook trout, and commercial brown trout) and predators (pike Esox lucius and pikeperch Sander lucioperca). They are calling for a ban of fish stocking on the streams where naturally self-reproducing brown trout populations exist. It is because studies have shown that angling pressure negatively affects salmonids [5,7]. The problem is that anglers buy permits, and they pay for the fishery management, meaning that without the anglers’ money, fishery managers will have less money for their conservation actions. If the brown trout populations need to be bolstered (e.g., after unexpected floods, droughts, or natural disasters), only eggs of local and genetically similar trout should be used. It is because the genetically pure populations have a better chance to survive [22], and genetical inbreeding is wrong from a conservation point of view [23].

While this study brought some insight into the successful management of brown trout populations, it does not provide a “silver bullet” for brown trout population management in the whole world. Only twenty managers were interviewed, which is not many. Unfortunately, it was impossible to interview more fishery managers who manage streams with sustainable trout populations, as some of them declined the interview. In addition, the brown trout populations in central Europe are different from those in southern and northern Europe, as they differ in migratory behaviour, size of individual fish, and ecology [24]. Therefore, the results of this study should be fully applied only in central Europe, but, for example, brown trout populations that were introduced outside of the trout native range (e.g., North America) suffered from the lack of habitats. The populations started thriving once the habitats for adult trout were improved [25].

5. Conclusions

In conclusion, the advice that the fishery managers gave is useful for anyone who wants to support local wild brown trout populations and has the authority to make decisions regarding the fishery management. The management of salmonid streams must cover the assessment of brown trout populations, formation of a strong committee that shields all those who want to protect them, ensuring their in-situ protection using legislative regulations, conserving the streams’ ability to retain water, and enforcing the stocking of young local trout only. However, even the fishery managers who gave the advice are somewhat sceptical because many other fishery managers still prefer the financial benefits of selling permits over fish conservation. As Steven Cooke said, “fishing is still not only about fun, but also about food [26].”