Bottom-Up Ecosystem Trophic Dynamics Determine Fish Production in the Northeast Pacific
School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada Science
(Impact Factor: 33.61).
06/2005; 308(5726):1280-4. DOI: 10.1126/science.1109049
We addressed the question of bottom-up versus top-down control of marine ecosystem trophic interactions by using annual fish catch data and satellite-derived (SeaWiFS) chlorophyll a measurements for the continental margin of western North America. Findings reveal a marked alongshore variation in retained primary production that is highly correlated with the alongshore variation in resident fish yield. The highest productivity occurs off the coasts of Washington and southern British Columbia. Zooplankton data for coastal British Columbia confirm strong bottom-up trophic linkages between phytoplankton, zooplankton, and resident fish, extending to regional areas as small as 10,000 square kilometers.
Available from: Chih-hao Hsieh
- "The trophic structure organizes the biological components of an ecosystem and channels the flow of nutrient and energy ; thus, its regulation is a central issue in ecological research (Ware and Thomson 2005; Casini et al. 2008; Llope et al. 2012). "
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ABSTRACT: Trophic structure and trophic transfer efficiency are among the most fundamental characteristics of an ecosystem. They characterize the transfer of nutrient and energy and are crucial in estimating the yield of harvestable biomass. In this study, we investigated the regulation of trophic structure (phytoplankton, zooplankton, and larval fish abundance) and biomass ratio of zooplankton to phytoplankton (as an indicator of transfer efficiency) in the East China Sea, one of the largest marginal seas in the world and an important fishing ground.
The results showed that when sea surface temperature was below 25°C, temperature co-acted with resource availability (zooplankton for larval fish and phytoplankton for zooplankton) in determining the trophic structure. When sea surface temperature was above 25°C, resource availability dominated the regulation of trophic structure. Biomass ratio of zooplankton to phytoplankton decreased with increasing phosphate concentration.
Our study suggested that the trophic structure of the East China Sea might be controlled by bottom-up processes, and this control is mediated by temperature.
12/2015; 54(1). DOI:10.1186/s40555-014-0089-0
- "Although identifying the importance of the differences represents an advancement in knowledge, whether in the case of Georges Bank cod–haddock or in other regions (e.g., Möllmann et al. 2005, 2008), the sum of the differences can also limit the identification of common principles that can serve to explain variations year-class strength. Despite the importance of trophic interactions in determining the production potential of marine ecosystems (Ryther 1969; Ware and Thomson 2005), there have been few research programs , such as the insights achieved in the dynamics of the Baltic Sea ecosystem (Möllmann et al. 2008), which have been able to clearly identify the relative roles of prey and predators on recruitment patterns or their links to climate-and anthropogenicinduced changes in a region's ecosystem. The only scenario from the previous section that yielded patterns of variations in survivorship consistent with observations that resulted in the occurrence of exceptionally strong and poor survival (i.e., year-class strength) and required a positive link between growth and mortality rates. "
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ABSTRACT: This essay contrasts the inferences about the patterns of size-dependent mortality in larval fish based on the traditional catch-curve approach with that achieved through the vertical life table method in an application to data from coastal Newfoundland. Although both approaches reveal that the average mortality rates decline with increasing body size, the rate of decline estimated using the vertical life table approach is much less pronounced than estimated from the catch-curve method. More importantly, however, is that on a case-by-case assessment the vertical life table reveals that mortality increases with increasing body size in 70% of the cases and declines in the remainder. Instances with greater rates of loss in larger individuals are consistent with larvae becoming more susceptible to the dominant planktivore in the study region. The contrasting results indicate that the patterns of change in mortality rates need to be measured over relatively short time and/or length intervals. Such inferences have important implications for the development of studies dealing with larval fish dynamics. To be effective and applicable, comparative analyses that aim to develop macroscopic principles for the early life stages of fish must take the local food web structure into consideration in order to gain appropriate understanding of the trophic interactions that most strongly affect losses from larval fish populations.
ICES Journal of Marine Science 09/2015; DOI:10.1093/icesjms/fsv160 · 2.38 Impact Factor
Available from: Susannah M Leahy
- "predation) versus bottom-up (e.g. availability of resources) processes is a difficult one to definitively answer, with much evidence for both cases (Estes et al. 1998; Pace et al. 1999; Richardson and Schoeman 2004; Ware and Thomson 2005; Myers et al. 2007; Frank 2008). The abundance and diversity of coral reef fishes are often thought to be largely controlled from the top-down, in part because of a rich history of apex-predator induced trophic cascades (Myers et al. 2007; Baum and Worm 2009; Ferretti et al. 2010; Rizzari et al. 2014), and in part because of the importance of herbivorous fishes and invertebrates in controlling macroalgal growth and in maintaining a coral-dominated system (Hughes 1994; Bellwood et al. 2006; Mumby et al. 2006; Hughes et al. 2007). "
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ABSTRACT: The question of whether biological systems are maintained by top-down versus bottom-up drivers is a recurring one in ecology. It is a particularly important question to address in the management of coral reefs, which are at risk from a variety of anthropogenic stressors. Here, we explicitly test whether the abundance of different feeding guilds of coral-associated Chaetodon butterflyfishes are controlled by top-down or bottom-up drivers, and we assess the relative influence of all statistically significant drivers. We find that the abundance and species richness of Chaetodon butterflyfishes are predominately determined by bottom-up drivers. The abundance of corallivores is primarily driven by availability of branching and tabular live corals, whereas the abundance of generalists is most strongly influenced by a negative association with macroalgal cover. We also find evidence of weak top-down control on the abundance of corallivorous butterflyfish by gape-limited mesopredators, but no such effects on generalist butterflyfish. Our findings indicate that conservation of coral reefs for Chaetodon butterflyfishes must include management at a larger spatial scale in order to reduce the effect of coral reef stressors such as declining water quality and climate change, but should also include implementation of fisheries management tools in order to increase local herbivory.
Marine and Freshwater Research 09/2015; DOI:10.1071/MF15012 · 1.47 Impact Factor
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