Relationships between climate, growth and fisheries production in a commercially exploited marine fish
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Climate variability can affect fish populations and fisheries production in numerous ways, including inducing measurable fluctuations in fish growth, condition, and fisheries production. Unfortunately, mechanisms driving these linkages are poorly understood for most exploited species, which hinders effective management. The purpose of this study was to use the Gulf Corvina (Cynoscion othonopterus), a heavily exploited marine fish in the Gulf of California, Mexico, as a model to investigate relationships between El Niño Southern Oscillation (ENSO) as measured by the Multivariate ENSO Index (MEI), sea surface temperature (SST), precipitation, drought as measured by the Palmer Drought Severity Index (PDSI), and river flow from the Morelos Dam with three parameters: adult fish condition, growth rate, and fisheries production. Adult fish condition was assessed by comparing annual variations in weight-length relationships of fish captured by the commercial fishery to each climate and environmental variable using an exponential model. Fish growth rate was measured using otolith chronologies for juveniles (years 0-2) and adult (years 3-10). Lastly, annual catch data from the commercial fishery was compared to each climate and environmental variable to examine relationships between climate and fisheries production. Results indicate that adult condition, juvenile growth rate and fisheries production are enhanced during El Niño conditions and increased SST. El Niño conditions during the birth year showed a positive relationship with fisheries landings at peak age of capture five years later, suggesting a possible linkage between juvenile recruitment, survivorship and future fisheries production. A weak positive relationship between river flow and growth rate in juveniles and adults was also found, which indicated that growth rate of both life history stages may be enhanced during strong El Niño years with high river flow. However, no relationship was found between precipitation and our parameters. Lastly, a positive relationship between decreased drought during the birth year and fisheries landings five years later indicated a freshwater influence on fisheries production. Our results indicate climate variability acting through El Niño events has a positive effect on growth, condition, fisheries production, and potentially juvenile recruitment suggesting the importance of both ocean climate variability and freshwater input on the Gulf Corvina.