Prey consumption estimates for salmon sharks
Kaitlyn A. Manishin A D , Kenneth J. Goldman B , Margaret Short C , Curry J. Cunningham A , Peter A. H. Westley A and Andrew C. Seitz A
+ Author Affiliations
- Author Affiliations
A College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, PO Box 757220, Fairbanks, AK 99775, USA.
B Alaska Department of Fish and Game, 3298 Douglas Place, Homer, AK 99603, USA.
C Department of Mathematics and Statistics, University of Alaska Fairbanks, PO Box 756660, Fairbanks, AK 99775, USA.
D Corresponding author. Email: kmanishin@alaska.edu
Marine and Freshwater Research 70(6) 824-833 https://doi.org/10.1071/MF18345
Submitted: 10 March 2018 Accepted: 16 November 2018 Published: 30 January 2019
Abstract
Top predators, such as salmon sharks (Lamna ditropis), can influence the abundance and population structure of organisms at lower trophic levels through direct effects, such as predation mortality, and indirect interactions. As a first step towards better understanding the average annual prey consumption for individual adult salmon sharks, we bracketed consumption estimates using three methods: (1) daily ration requirement; (2) bioenergetic mass balance; and (3) a Bayesian model of shark growth. In the first method, we applied ration estimates for related lamnid shark species that yielded salmon shark estimates of 1461 and 2202 kg year–1. The second method used a mass–balance technique to incorporate life history information from salmon sharks and physiological parameters from other species and produced estimates of 1870, 2070, 1610 and 1762 kg year–1, depending on assumed diet. Growth modelling used salmon shark growth histories and yielded estimates of 16 900 or 20 800 kg year–1, depending on assumed assimilation efficiency. Of the consumption estimates, those from the mass–balance technique may be the most realistic because they incorporated salmon shark life history data and do not produce extreme values. Taken as a whole, these estimates suggest that salmon sharks have similar energetic requirements to piscivorous marine mammals.
Additional keywords: apex predator, bioenergetics, endothermy metabolism, Lamna ditropis, prey requirements, top-down.
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