Abstract
Although considerable knowledge has been gathered regarding the role of fish in cycling and translocation of nutrients across ecosystem boundaries, little information is available on how the energy obtained from different ecosystems is temporally allocated in fish bodies. Although in theory, limitations on energy budgets promote the existence of a trade-off between energy allocated to reproduction and somatic growth, this trade-off has rarely been found under natural conditions. Combining information on RNA:DNA ratios and carbon and nitrogen stable-isotope analyses we were able to achieve novel insights into the reproductive allocation of diamond mullet (Liza alata), a catadromous, widely distributed herbivorous-detritivorous fish. Although diamond mullet were in better condition during the wet season, most reproductive allocation occurred during the dry season when resources are limited and fish have poorer body condition. We found a strong trade-off between reproductive and somatic investment. Values of δ13C from reproductive and somatic tissues were correlated, probably because δ13C in food resources between dry and wet seasons do not differ markedly. On the other hand, data for δ15N showed that gonads are more correlated to muscle, a slow turnover tissue, suggesting long term synthesis of reproductive tissues. In combination, these lines of evidence suggest that L. alata is a capital breeder which shows temporal uncoupling of resource ingestion, energy storage and later allocation to reproduction.
Highlights
Linkages among habitats and the flux of matter across ecosystem boundaries have important implications for biomass production of animals and plants [1,2,3,4]
We found no evidence suggesting that the site of capture influenced any of the patterns explained regarding body condition, RNA:DNA ratios and δ15N of different tissues (F0.067 in all cases)
Most individuals were heavier for a given length, and during the dry season they were lighter than expected for their length (S2 Fig)
Summary
Linkages among habitats and the flux of matter across ecosystem boundaries have important implications for biomass production of animals and plants [1,2,3,4]. As part of spawning movements and migrations, many species of fish cross ecosystem boundaries. In the wet-dry tropics, fish that typically live in river channels, waterholes and estuaries during the dry season move onto floodplains during the wet season, where they take advantage of PLOS ONE | DOI:10.1371/journal.pone.0150082. Energy Allocation to Reproduction in Liza alata. Gov.br/web/csf-eng/) to visit the Australian Rivers Institute. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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