Exploitation Currency among Artisanal Bait Fishers;Are Intertidal Bait Harvesters Optimal Foragers?Some Consideration for Holistic Management

Abstract

Optimal foragers target prey with superior energetic returns,and suchmetricsunderlie mostmanagement interventions. However, tropical artisanalbait arvestedbyintertidalexcavation and collection,enhance fish landings,and hence determinants to choice remain conjectural.Fisher interviewwereusedto infer bait preference, and monitoringbait and fish landings, tocompute energetic and fishery profitability.Harvesting of hermitcrabs,mangrove whelk and polychaetesfrom mangrove and mudflat, andsubsequent fish landings, werequantifiedat Mida creek, Kenya.Deshelledhermit crabweightwasestimatedby regression,anddocumented energycontent and fishing fixed costs,wereused tocomputeenergetic and fisheryprofitability. Results show that despite whelks being least targeted (<5%),theyhadsignificantly (P<0.0001),higher harvesting(0.87 kg.hr-1) andenergetic returns (9750kcal),compared to more popular,polychaete andhermit crabs.Mudflat polychaetes(preference>25%),recorded the lowestharvest return (0.13 kg.hr-1)andharvestenergeticconversion(0.87).Nonetheless,polychaete and hermitharvesters,hadhigherfish landings (>2kg.d-1),correspondingto higherincome(>3$.d-1)andprofitability(>2.0),compared to whelk fishers. Therefore, fishery returns, rather thanconventional harvestingmetrics (e.g. energy), are important determinantstobait choiceandharvesters maypursue preferred bait, dueto perceivedfishery gains, irrespective of harvesting constrains, with consequences onbiota and ecosystem integrity.Bait management interventions that not onlyignorethe interrelatedness of theforaging and fishing grounds, but also the realities of fishery profitability, will inevitably impact lifestyle.