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Marine Ecology Progress Series

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MEPS 637:225-235 (2020)  -  DOI:

Relationship between morphometrics and trophic levels in deep-sea fishes

Monique A. Ladds1,2,*, Matthew H. Pinkerton3, Emily Jones2, Leonardo M. Durante4, Matthew R. Dunn3

1Marine Ecosystems Team, Department of Conservation, Wellington 6011, New Zealand
2Department of Mathematics and Statistics, Victoria University of Wellington, Kelburn 6012, New Zealand
3National Institute of Water and Atmospheric Research Ltd., Wellington 6021, New Zealand
4Department of Marine Science, University of Otago, Dunedin 9054, Otago, New Zealand
*Corresponding author:

ABSTRACT: Marine food webs are structured, in part, by predator gape size. Species found in deep-sea environments may have evolved such that they can consume prey of a wide range of sizes, to maximise resource intake in a low-productivity ecosystem. Estimates of gape size are central to some types of ecosystem model that determine which prey are available to predators, but cannot always be measured directly. Deep-sea species are hypothesized to have larger gape sizes than shallower-water species relative to their body size and, because of pronounced adaptive foraging behaviour, show only a weak relationship between gape size and trophic level. Here we present new data describing selective morphological measurements and gape sizes of 134 osteichthyan and chondrichthyan species from the deep sea (200-1300 m) off New Zealand. We describe how gape size (height, width and area) varied with factors including fish size, taxonomy (class and order within a class) and trophic level estimated from stable isotopes. For deep-sea species, there was a strong relationship between gape size and fish size, better predicted by body mass than total length, which varied by taxonomic group. Results show that predictions of gape size can be made from commonly measured morphological variables. No relationship between gape size and trophic level was found, likely a reflection of using trophic level estimates from stable isotopes as opposed to the commonly used estimates from FishBase. These results support the hypothesis that deep-sea fish are generalists within their environment, including suspected scavenging, even at the highest trophic levels.

KEY WORDS: Trophic level · Isotopic ecology · Gape limitation · Deep-sea fish · Ecosystem modelling · Generalists

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Cite this article as: Ladds MA, Pinkerton MH, Jones E, Durante LM, Dunn MR (2020) Relationship between morphometrics and trophic levels in deep-sea fishes. Mar Ecol Prog Ser 637:225-235.

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