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Big mamma fish give proportionally bigger reproductive outputs

American Association for the Advancement of Science

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IMAGE: This infographic shows how the scaling of reproductive-energy output in marine fishes affects our understanding of fisheries management, the efficacy of marine protected areas, and the impacts of climate change... view more 

Credit: © Centre for Geometric Biology (Monash University)

Even accounting for their proportionate size, bigger female fish produce many more offspring than smaller fish, a new study reveals. The results hold implications for fisheries managers, since climate change is expected to reduce the size of fish (and thus the number of their offspring) in many regions around the globe. The question of whether reproduction scales with size has been hotly debated. Theories and fisheries models assume that the reproductive output of one 2-kilogram (kg) fish is equal to that of two 1-kg fish; yet field biologists have repeatedly suggested that fecundity of fish may increase disproportionately with body mass. To better understand this likelihood, Diego R. Barneche et al. analyzed the total reproductive-energy output of 342 species of marine fish. Indeed, in the majority of species, they found a scaling pattern where bigger mothers produce exponentially more offspring. For example, a single 30-kg female produces more eggs than about 28 2-kg females (that collectively weigh 56 kg); as well, a batch of eggs from a 30-kg female harbors 37 times the total energy content of a batch from her 2-kg counterpart. These results emphasize the importance of larger fish for replenishing marine fish populations, the authors say. Estimates of size reductions for the Atlantic mackerel (Scomber scombrus) predicted to occur in the face of climate change, would result in a 50% per capita reduction in fecundity for the species, say the authors. In good news, marine protected areas have been found to increase fish size, pointing to at least one solution for more sustainable fisheries in the future.

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