Quantifying energy intake in Pacific bluefin tuna (Thunnus orientalis) using the heat increment of feeding

Abstract

SUMMARYUsing implanted archival tags, we examined the effects of meal caloric value, food type (sardine or squid) and ambient temperature on the magnitude and duration of the heat increment of feeding in three captive juvenile Pacific bluefin tuna. The objective of our study was to develop a model that can be used to estimate energy intake in wild fish of similar body mass. Both the magnitude and duration of the heat increment of feeding (measured by visceral warming) showed a strong positive correlation with the caloric value of the ingested meal. Controlling for meal caloric value, the extent of visceral warming was significantly greater at lower ambient temperature. The extent of visceral warming was also significantly higher for squid meals compared with sardine meals. By using a hierarchical Bayesian model to analyze our data and treating individuals as random effects, we demonstrate how increases in visceral temperature can be used to estimate the energy intake of wild Pacific bluefin tuna of similar body mass to the individuals used in our study. Supplementary material available online at

Assessing niche width of endothermic fish from genes to ecosystem

“…2). Estimates of kJ stomach −1 were similar to results using the same methods in similarly sized tunas (yellowfin and bigeye tuna) in other regions (24); however, visceral endothermy in PBFT has been associated with more rapid digestion rates than other tunas (25,26). Higher digestion rates could cause PBFT stomach contents to evacuate more rapidly and thus represent shorter time frames of recent diet.…”

Bioenergetics of captive Pacific bluefin tuna (Thunnus orientalis)

“…Data represented in Table 4, including wild data from Shimose et al (2009). (between 46 and 201 kJ −1 · kg −1 · day) but at greater frequency (daily vs. 3 days · week −1 ) than the captive tunas in this study (Whitlock et al, 2013). Concise estimates of food conversion ratios (FCRs) in pen-raised bluefin tuna are difficult to obtain due to a lack of data on fish size, biomass, and amount of food actually consumed.…”

“…At the TRCC, the emphasis was on studying tuna respiration under controlled laboratory conditions of temperature, water quality, and swimming speed for extended periods of time (Blank et al, 2007a,b). More recently, TRCC researchers focused on quantifying and modeling the specific dynamic action (SDA) of Pacific bluefin tuna (Clark et al, 2010;Walli et al 2007;Whitlock et al, 2013).…”

“…The processes of ingestion, digestion, absorption, and assimilation are now partially quantified in two species of bluefin tunas. The energy expended following a feeding event, also known as specific dynamic action, has been examined in two studies, one on Southern bluefin (Thunnus maccoyii; Fitzgibbon and Seymour, 2009) and one on Pacific bluefin tuna (Clark et al, 2010;Walli et al, 2007;Whitlock et al, 2013). Other aspects of fish bioenergetics including the energy available for growth, or retained energy (RE), ingested energy (IE), routine metabolic rate (RMR), active metabolic rate (AMR), and excretion and egestion (EE) have also been investigated (Beamish et al, 1975;Brett and Groves, 1979;Halver and Hardy, 2002;Kitchell et al, 1978).…”

Quantifying mercury isotope dynamics in captive Pacific bluefin tuna (Thunnus orientalis)

“…In fact, we observed a decreasing trend in THg concentration in the PBFT with respect to time in captivity (Figure 1). Based on these observations, we propose that the excretion of MMHg during muscle tissue turnover is most likely responsible for the reduction in THg concentration and the negative d The isotopic variability observed in sardine and squid is likely due to a combined effect of individual differences in life history (i.e., age, trophic position, size) (Whitlock et al, 2013) and temporal variation in environmental conditions. Based on this likelihood, it is possible that the individual PBFT with variable feeding preferences and/or consumption rates were exposed to dietary mixtures with slightly different d…”