1 research outputs found
Effects of environmental conditions and jellyfish blooms on small pelagic fish and fisheries from the Western Mediterranean Sea
Sardine and anchovy have shown important changes in landings, biomass, abundance and body condition with
time in the Western Mediterranean Sea. Several hypotheses have been proposed to explain these changes,
including the negative interaction with jellyfish blooms. Increases in jellyfish blooms may be one of the reasons
for a decline in these fish stocks because several jellyfish species have been shown to feed on fish larvae and
juveniles. The main aim of the present study was to test the plausible relationship between jellyfish blooms and
stock dynamics (abundance, biomass, and fitness) of anchovy and sardine, and its fisheries within an ecological
context of the western Mediterranean Sea. Our main hypothesis was that jellyfish blooms, in combination with
other environmental drivers, could have negative effects due to their predation on early stages of small pelagic
fish (direct mortality) or due to predation on zooplankton, which is also prey of the small pelagic fish at different
ontogenetic stages (direct competition). To test our hypothesis, we developed Bayesian Generalized Linear Mixed
Models to compare landings, biomass, abundance, and Kn condition factor of both species with several climatic
indices, oceanographic variables, and the occurrences of jellyfish blooms. Our results revealed that the jellyfish
bloom occurrence had a high probability of negatively and broadly affecting both species in addition to changes
in environmental conditions. This suggests that jellyfish blooms should be added to the likely causes of change
when analyzing small pelagic fish change.Postprint2,24