Climate, Fish Growth, and Fisheries Production

Climate variability can affect fish populations and fisheries production in numerous ways, including inducing measurable fluctuations in fish growth, condition, and fisheries production. Unfortunately, linkages between and mechanisms that drive climate, fish populations, and fisheries 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 length to weight ratios 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 1-2) 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.

Map of spatial correlation of Cynoscion othonopterus fisheries production with Sea Surface Temperature (SST). April-December averaged SST from Hadley Centre Sea Ice and Sea Surface Temperature (HadISST1) 1870-now 1º reconstruction for the Sea of Cortez north of the Midriff islands was correlated fisheries production of Gulf Corvina five years later (1998-2015). Warmer colors indicate positive correlations and cooler colors indicate negative correlations. Map was created in KNMI Climate Explorer (Trouet & Oldenborgh, 2013) using climate data (SST) and our fisheries production data.

 

Results indicate that adult condition and juvenile growth rate are enhanced during El Niño conditions. Additionally, El Niño conditions during the birth year showed a positive relationship with fisheries production at peak age of capture five years later. A positive relationship with river flow and growth rate in juveniles and adults was also found. However, no relationship with precipitation was found with fish condition, growth rate, or fisheries production. Lastly, a positive relationship between decreased drought (PDSI) at birth year and fisheries production five years later, indicated a freshwater influence on fisheries production. Based on our results, inter-annual climate variability acting as El Niño has a positive effect on the Gulf Corvina. A possible driver may be freshwater input from increased river flow during El Niño events which enhances growth and fisheries production. These results suggest that relationships between these factors can be used in a predictive manner to adjust harvest limits based on climate variability.