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Changing distribution and abundance of small pelagic fishes may drive changes in predator distributions, affecting predator availability to fisheries and surveys. However, small pelagics are difficult to survey directly, so we developed a novel method of assessing the aggregate abundance of 21 small pelagic forage taxa via predator stomach contents. We used stomach contents collected from 22 piscivore species captured by multiple bottom trawl surveys within a vector autoregressive spatio-temporal model to assess trends of small pelagics on the Northeast US shelf. The goal was to develop a spatial "forage index" to inform survey and (or) fishery availability in the western North Atlantic bluefish (Pomatomus saltatrix) stock assessment. This spatially resolved index compared favorably with more traditional design-based survey biomass indices for forage species well sampled by surveys. However, our stomach content-based index better represented smaller unmanaged forage species that surveys are not designed to capture. The stomach-based forage index helped explain bluefish availability to the recreational fishery for stock assessment and provided insight into pelagic forage trends throughout the regional ecosystem. [ABSTRACT FROM AUTHOR]

Changes in temperature alter the viscosity of fluids, which impacts the force needed to move and the diffusion rates of gases. This is particularly salient for organisms that operate at mid to low Reynolds numbers. In this study, we investigated the independent effects of changes in temperature and viscosity on oxygen consumption rates of two coastal copepods (Acartia tonsa and Parvocalanus crassirostris) and used bioenergetic models to predict how these patterns could influence copepods in the natural environment. We found that only temperature influenced copepod oxygen consumption rates, indicating that copepods were not impacted by reduced oxygen diffusivity or increased energetics of movement resulting from higher seawater viscosity. We developed energy budgets based on novel respiration experiments in conjunction with data from the literature and found that cold temperatures do not result in higher scope for growth, because decreased metabolic costs are offset by reduced feeding capability. Our energy budgets imply that observed copepod temperature ranges in natural waters match theoretical ranges of optimal net carbon assimilation. At cold temperatures, feeding on motile prey yielded higher net carbon assimilation compared to feeding on non-motile prey, implying that motile prey are more favorable and may be actively selected for at cold temperatures. Finally, our models predicted that A. tonsa had a higher maximum net carbon assimilation as a percentage of body mass, indicating that copepods that use a similar sink-and-wait feeding strategy may be better able to exploit ephemeral food sources compared to continuous-swimming copepods such as P. crassirostris., Introduction Cold temperature slows the metabolism of poikilotherms (Marshall, 1973; Ikeda et al., 2001; Ikeda, 2014). This has long been assumed to result from the thermal effect of temperature on [...]

Somelarval experiences can produce "latent effects" on post-metamorphic growth or survival. While it is known that periods of starvation during larval development can cause such latent effects, the effect of larval diet on post-metamorphic growth has not been studied. As global climate change and ocean acidification are expected to decrease phytoplankton concentrations and alter both phytoplankton species composition and nutritional characteristics, we examined the impact of 3 phytoplankton species (Isochrysis galbana, clone T-ISO; Pavlova lutheri, clone MONO; and Dunaliella tertiolecta, clone DUN) on larval growth and subsequent post-metamorphic fitness in the slippersnail Crepidula fornicata. Once larvae metamorphosed, the juveniles were all reared on the diet that produced the fastest growth, T-ISO, to look for latent effects of larval diet on juvenile growth. In all experiments, larvae grew most quickly on T-ISO; diet did not affect relative rates of shell and tissue growth. In 2 of the 4 experiments conducted on the effects of diet quality, larvae reared on T-ISO metamorphosed into juveniles that grew significantly faster than those that had been raised on the other phytoplankton species, indicating clear latent effects of dietary experience and suggesting parent-related genetic variation in susceptibility to this type of stress. Rearing larvae at a very low food concentration of T-ISO (1 x 10.sup.4 cells ml.sup.-1) until metamorphosis also produced severe latent effects on juvenile growth, reducing juvenile growth rates by more than 30 %. These data provide yet another example of how stresses experienced during larval development can influence post-metamorphic performance, and add another level of complexity to attempts at predicting the future consequences of environmental change on marine community structure and species interactions., Author(s): Jan A. Pechenik [sup.1] , Abigail S. Tyrell [sup.2] Author Affiliations: (Aff1) grid.429997.8, 0000000419367531, Biology Department, Tufts University Medford, , 02155, Medford, MA, USA (Aff2) grid.36425.36, 0000000122169681, The School [...]