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Trait-based ecology is a rapidly growing approach for developing insights and predictions for data-poor species. Caudal tail fin shape has the potential to reveal much about the energetics, activity and ecology of fishes and can be rapidly measured from field guides, which is particularly helpful for data-sparse species. One outstanding question is whether swimming speed in sharks is related to two morphological traits: caudal fin aspect ratio (CFAR, height2/tail area) and caudal lobe asymmetry ratio (CLAR). We derived both metrics from the species drawings in Sharks of the world (Ebert et al. 2013 Sharks of the world: a fully illustrated guide) and related fin shape to two published datasets of (1) instantaneous swimming speeds (Jacoby et al. 2015 Biol. Lett. 11, 20150781 (doi:10.1098/rsbl.2015.0781)) and (2) cruising speeds (Harding et al. 2021 Funct. Ecol. 35, 1951–1959 (doi:10.1111/1365-2435.13869)) for 28 total unique shark species. Both estimates of swimming speed were positively related to CFAR (and weakly negatively to CLAR). Hence, shark species with larger CFAR and more symmetric tails (low CLAR) tended to be faster-moving and have higher average speeds. This relationship demonstrates the opportunity to use tail shape as an easily measured trait to index shark swimming speed to broader trait-based analyses of ecological function and extinction risk.

This study presents a multiple regression of the parameter K, i.e., the rate at which the asymptote of the von Bertalanffy Growth Function (VBGF) is approached vs. the asymptotic weight (W∞), environmental temperature (T'), and an index of activity level (the aspect ratio of the caudal fin, or A) in 4251 populations and 1155 fish species extracted from FishBase (www.fishbase.org). The resulting model was log(K) = 3.674 − 0.2362·log(W∞) − 1.035·T' + 0.2838·log(A), with K in year−1, W∞ in g, and T' = −1000/Kelvin. It explained 57 % of the variance in the dataset, with all partial slopes significantly different from zero (p < 0.01), and having the expected signs. Thus, temperature decreases the asymptotic size of fish, but increases their parameter K, and thus decreases traits associated with K, e.g., longevity. Also, our model suggests that A, which take values around 1 in less active fish such as groupers and 8–9 in active swimmers such as tuna, correlates with K values. This implies that active fish have large gill areas supplying the oxygen required for both a high level of activity and rapid growth, both supported by a high feeding rate, which is what we know of these fishes. [ABSTRACT FROM AUTHOR]

Context: Remotely operated vehicles (ROVs) are routinely used to inspect oil and gas infrastructure for industry's operational purposes and scientists utilise this video footage to understand how fish interact with these structures. Aim: This study aims to clarify how fish abundance data obtained from ROV video compares to that collected using baited remote underwater video (BRUV). Method: This study compares fish assemblages observed using an industry ROV and BRUVs along a pipeline located in 130-m water depth in north-west Australia. Key results: Both methods recorded 22 species of fish, however each method observed 15 unique species. The fish assemblage recorded by each method was statistically different at all sites. Differences in the fish assemblages correlated with the caudal fin aspect ratio of each species: the mean caudal fin aspect ratio of fish recorded using BRUVs was 2.81, compared to 1.87 for ROV observations. Conclusions: We interpret this to indicate differences in site attachment, with site-attached species having generally lower caudal fin aspect ratios that are associated with slower swimming speeds with a burst and glide pattern. Implications: Our results show that these remote video methods predominantly sample different fish assemblages and demonstrates how different sampling methods can provide different insights into fish interactions with subsea infrastructure. Understanding the ecosystem around subsea oil and gas infrastructure is imperative to decommissioning. Our study found differences in fish assemblage data derived from industry remotely operated vehicle (ROV) video and baited remote underwater video (BRUV) collected along a subsea pipeline. Both methods sampled the same number of species, but ROV sampled more site attached species compared to BRUV. [ABSTRACT FROM AUTHOR]

Trait-based ecology is a rapidly growing approach for developing insights and predictions for data-poor species. Caudal tail fin shape has the potential to reveal much about the energetics, activity and ecology of fishes and can be rapidly measured from field guides, which is particularly helpful for data-sparse species. One outstanding question is whether swimming speed in sharks is related to two morphological traits: caudal fin aspect ratio (CFAR, height 2 /tail area) and caudal lobe asymmetry ratio (CLAR). We derived both metrics from the species drawings in Sharks of the world (Ebert et al. 2013 Sharks of the world: a fully illustrated guide ) and related fin shape to two published datasets of (1) instantaneous swimming speeds (Jacoby et al. 2015 Biol. Lett. 11 , 20150781 (doi:10.1098/rsbl.2015.0781)) and (2) cruising speeds (Harding et al. 2021 Funct. Ecol. 35 , 1951-1959 (doi:10.1111/1365-2435.13869)) for 28 total unique shark species. Both estimates of swimming speed were positively related to CFAR (and weakly negatively to CLAR). Hence, shark species with larger CFAR and more symmetric tails (low CLAR) tended to be faster-moving and have higher average speeds. This relationship demonstrates the opportunity to use tail shape as an easily measured trait to index shark swimming speed to broader trait-based analyses of ecological function and extinction risk., Competing Interests: The authors declare they have no competing interests., (© 2023 The Authors.)