Spatial variation in allometric growth of invasive lionfish has management implications

Lionfish (Pterois volitans/miles) are an invasive species in the Western Atlantic and the Caribbean. Improving management of invasive lionfish populations requires accurate total biomass estimates, which depend on accurate estimates of allometric growth; sedentary species like lionfish often exhibit high levels of spatial variation in life history characteristics. We reviewed 17 published length-weight relationships for lionfish taken throughout their invasive range and found regional differences that led to significant misestimates when calculating weight from length observations. The spatial pattern we observed is consistent with findings from other studies focused on genetics or length-at-age. Here, the use of ex situ parameter values resulted in total biomass estimates between 76.2% and 140% of true observed biomass, and up to a threefold under- or overestimation of total weight for an individual organism. These findings can have implications for management in terms of predicting effects on local ecosystems, evaluating the effectiveness of removal programs, or estimating biomass available for harvest.


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Lionfish (Pterois volitans/miles complex) are an invasive species in the Western Atlantic Ocean and 23 Caribbean Sea, likely introduced through release of aquarium-kept organisms (Betancur-R et al., 2011). 24 Lionfish are the first invasive marine vertebrates established along these coasts (Schofield, 2009(Schofield, , 2010;   Our objective was to quantify the magnitude of error caused by using ex situ parameter values when 71 estimating lionfish weight from length observations. In this study, we calculated and reported the first   Table 1). Sampling locations included wall and carpet reefs at depths between 5.7 m and 102 38.1 m. The use of hand nets prevented any weight loss due to bleeding and allowed better representation The weight-at-length relationship for lionfish in the central Mexican Caribbean was calculated with 105 the allometric growth function: Where a is the ponderal index and b is the scaling exponent or allometric parameter. We linearized 107 the equation using log 10 -transformation and estimated the coefficients using an Ordinary Least Squares

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Regression with a heteroskedastic-robust standard error correction (Zeileis, 2004 reported parameters as mm-to-g conversions when they were in fact cm-to-g conversions. We standardized 113 each study by converting coefficients and report all parameters as TL (mm) to TW (g) conversions. 114 We obtained a total of 18 parameter pairs by combining length-weight parameters extracted from the 115 literature and the additional pair calculated here (Table 1). Recall that the objective of this study is not to 116 describe differences in the length-weight relationship between populations (which would require access 117 to raw data), but rather to assess how ex situ parameter values influence the accuracy of weight estimates  Manuscript to be reviewed

RESULTS
The length-weight relationship for organisms from the central Mexican Caribbean (Fig 2) Fig 4). If we examined biomass (i.e., summing across 147 all 109 organisms) instead of mean ratios, total biomass estimates were 76.2% (4,363.53 g) and 140% 148 (8,039.96 g) of true observed biomass (5,729.34 g). Parameters for this study estimate total biomass at 149 98% of observed biomass (Fig 5). These misestimates come from the two most extreme sets of parameters, 150 but results varied consistently across locations (Figs 4 and 5). Overall, the use of ex situ parameters led to 151 significantly erroneous estimates of individual weight and total biomass for lionfish. Manuscript to be reviewed

DISCUSSION
Our results suggest that lionfish exhibit highly variable, spatially heterogeneous allometric relationships 164 across their invaded range, and that this variation is relevant for managing invasions. Moreover, we show 165 that the use of ex situ parameter values may lead to highly biased weight and total biomass estimates.

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Our comparison of observed weights to those predicted with locally-informed parameters and ex situ 167 parameters showed that weight of an individual lionfish can be overestimated by more than threefold, 168 highlighting the need to use local information. Here we discuss the implications of our findings, possible 169 shortcommings in our analyses, and highlight potential future research directions. needed to successfully manage an invasion, we must acknowledge and understand regional biological 177 differences in important variables such as allometric growth parameters. 178 We detected substantial differences in weight-at-length between organisms from the Caribbean, Gulf 179 of Mexico, and Western Atlantic. Groupings of predicted-to-observed weight ratios identified in our post 180 hoc testing aligned with the spatial distribution of the examined studies, suggesting that these differences 181 may be mediated by space. These regional allometric differences mirror similar patterns in length-at-age  Table 2 for an extended version of Table 1). The magnitude of the bias discovered in this 191 study and our lack of understanding the sources driving spatial variation for lionfish highlights the need to 192 simultaneously collect length-weight information across the invaded range to test for spatially-induced 193 patterns and to link these findings to previously suggested environmental and genetic structures. Such an 194 endeavor would provide insight into lionfish biology and better inform management. However, while we 195 could not evaluate how these factors influenced length-weight estimates from previous studies without 196 raw data, we still show that a lack of locally-calculated parameters can induce significant bias when 197 calculating weight from length observations. We demonstrate the importance of using in situ parameters 198 to obtain accurate weight estimates regardless of the underlying mechanisms driving variation between 199 populations.
lionfish population to recover to 90% of its initial biomass after removals ceased.

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Here, we show that using one set of length-weight parameters versus another for a given length 217 can result in more than a threefold under-or overestimation of total weight for individual fish, and that 218 total biomass estimates may range between 76% and 140% of true observed biomass. These differences who provided help to collect samples. We are grateful for comments raised by the editor and two 227 anonymous reviewers, which significantly increased the quality of this work.

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age and growth patterns of invasive lionfish among three ecoregions of the northern gulf of mexico. In