Relationships Between CPUE of Major Commercial Cephalopods and Major Environmental Factors in Coastal Bottom Trawls of Northern West Africa Based on Boosted Regression Trees
[Objective]This paper investigates the pattern of the effects of different environmental factors on catch per unit effort(CPUE)of major commercial cephalopods(octopus,cuttlefish,and squid)off the coast of northern West Africa,to provide a reference for rational planning of commercial fishing production and scientific fishery management,among others.[Method]The Boosted Regression Trees(BRT)was used to analyze the response patterns of major commercial cephalopods to environmental factors(namely Sea Surface Temperature(SST),Chlorophyll mass concentration,Sea Surface Salinity(SSS),Sea Surface Height Anomaly(SSHA),dissolved oxygen concentration,precipitation,longitude,latitude,depth,distance from shore and time)based on data from bottom trawl fisheries off the coast of northern West Africa from 2019―2021.[Result and Conclusion]The BRT model has significant advantages over traditional models in fishery research,especially in data processing In this study,relative importance values were used to classify the strength of the effects of 11 factors on cephalopod CPUE:strong importance(more than 10%),moderate importance(5%― 10%),and weak importance(less than 5%).The results of BRT fitting showed that SST,latitude,precipitation,and distance from shore had strong importance tooctopus CPUE,latitude,SST,and chlorophyll mass concentration had strong importance to cuttlefish CPUE,while precipitation,dissolved oxygen concentration,and SST had strong importance to squid CPUE.Latitude had a strong importance to CPUE of octopus and squid,with higher CPUE occurring south of 24°N(octopus)and between 23°N ― 27°N(cuttlefish),respectively;Distance from shore had more than moderate importance for both octopus and squid CPUE,with higher CPUE occurring within 30 ― 70 km from shore;Among the three species,squid CPUE was most affected by time,with higher CPUE occurring in January and July.Among the environmental factors,SST had a strong effect on all three cephalopods,with a relative importance of more than 20%,with opposite effects onoctopus and cuttlefish,with octopus favoring warmer water and cuttlefish colder water;Dissolved oxygen concentration was positively correlated with squid CPUE;Chlorophyll mass concentration had a strong effect on CPUE of cuttlefish,and CPUE was stable at lower chlorophyll mass concentrations,but gradually decreased when the mass concentration exceeded 4 mg·m-3.The effect of precipitation on CPUE of all three cephalopods was above general importance,and squid CPUE increased with increasing precipitation,while octopus and cuttlefish CPUE first increased and then decreased.
West Africabottom trawlcephalopodsBoosted Regression TreesCPUEenvironmental factors
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