Hot off the press: Dolphin Prey Availability and Calorific Value

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On behalf of MUCRU and the South West Marine Research Program, we are happy to announce our recent publication on dolphin prey availability and calorific value:

Title: Dolphin Prey Availability and Calorific Value in an Estuarine and Coastal Environment

Citation: McCluskey, S.M., Bejder, L. and Loneragan, N.R. 2016. Dolphin Prey Availability and Calorific Value in an Estuarine and Coastal Environment. Frontiers in Marine Science 3:30. doi: 10.3389/fmars.2016.00030

Abstract

Prey density has long been associated with prey profitability for a predator, but prey quality has seldom been quantified. We assessed the potential prey availability and calorific value for Indo-Pacific bottlenose dolphins (Tursiops aduncus) in an estuarine and coastal environment of temperate south-western Australia. Fish were sampled using three methods (21.5 m beach seine, multi-mesh gillnet, and fish traps), across three regions (Estuary, Bay, and Ocean) in the study area. The total biomass and numbers of all species and those of potential dolphin prey were determined in austral summers and winters between 2007 and 2010. The calorific value of 19 species was determined by bomb calorimetry. The aim of the research was to evaluate the significance of prey availability in explaining the higher abundance of dolphins in the region in summer vs. winter across years. A higher abundance of prey was captured in the summer (mean of two summer seasons 12,080 ± 160) than in the winter (mean of two winter seasons = 7358 ± 343) using the same number of gear sets in each season and year. In contrast, higher biomass and higher energy rich prey were captured during winters than during summers, when fewer dolphins are present in the area. Variability was significant between season and region for the gillnet (p < 0.01), and seine (p < 0.01). The interaction of season and region was also significant for the calorific content captured by the traps (p < 0.03), and between the seasons for biomass of the trap catch (p < 0.02). The dolphin mother and calf pairs that remain in the Estuary and Bay year round may be sustained by the higher quality, and generally larger, if lesser abundant, prey in the winter months. Furthermore, factors such as predator avoidance and mating opportunities are likely to influence patterns of local dolphin abundance. This study provides insights into the complex dynamics of predator—prey interactions, and highlights the importance for a better understanding of prey abundance, distribution and calorific content in explaining the spatial ecology of large apex predators.

Prey catch differences

Figure: Mean biomass (±1 SE) of prey caught per trap for (A) total biomass; (B) biomass of PDP; and (C) KJ per trap in the Ocean, Bay, and Estuary. N.S. = Not Sampled.

Download the paper:

The publication can be freely downloaded from Frontiers in Marine Science, or alternatively, or send an email to Shannon McCluskey.

Other SWMRP project publications:

Our publications made possible through the South West Marine Research Program:

Project Funding:

Funding was generously provided by the South West Marine Research Program partners, including Bemax Cable Sands, Bunbury Dolphin Discovery Centre, Bunbury Port Authority, City of Bunbury, Cristal Global, the Department of Parks and Wildlife in Western Australia, IIuka, Bemax, Millard Marine, Naturaliste Charters, Newmont Boddington Gold, South West Development Commission, WA Plantation Resources and BHP Billiton Worsley Alumina.

Lars Bejder PhD
Lars Bejder PhD
Professor Lars Bejder PhD is the Research Leader of the Murdoch University Cetacean Research Unit.
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