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MEPS prepress abstract   -  DOI:

Relationship between morphometrics and trophic levels in deep-sea fishes

Monique A. Ladds* Matthew H. Pinkerton, Emily Jones, Leonardo M. Durante, Matthew R. Dunn

*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, where they determine which prey are available to predators, but cannot always be measured directly. Deep-sea species are hypothesised to have larger gape sizes than shallower-water species relative to their body size and, because of pronounced adaptive foraging behaviour, only a weak relationship between gape size and trophic level. Here, we present new data describing selective morphological measurements and gape sizes of 134 osteichthyes 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 estimated trophic level 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.