How did fisheries resource Balistes capriscus (Teleostei: Balistidae) disappear in coastal waters of Ghana?
Abstract
The paper assessed the possible reasons for which Balistes capriscus (grey triggerfish) resource disappeared in coastal waters of Ghana. The study analysed relationships between seasonal maxima, minima and the difference between maximum and minimum sea surface temperatures and grey triggerfish landings in coastal waters of Ghana. The study assessed a possible relationship between Balistes catch and fishing effort employed in the exploitation of the resource and the possible scenarios that might have caused the collapse of the fishery. Catch-effort data of inshore Balistes (fish caught by inshore fishery) in Ghanaian waters from 1972 to 1991 was analysed. Temperature partitioning (Tp) was identified in between the period Balistes biomass increased with maximum temperature recorded from 1972 to 1976 and period Balistes biomass decreased with rising maximum temperature recorded from 1985 to 1989 in coastal waters of Ghana. A critical mean maximum temperature (Tc) was recorded in 1987 (Tc = 28.72 °C) in Ghanaian waters and thereafter Balistes fishery resource declined to virtually zero biomass in 1989. Three probable scenarios which consider possible migration of triggerfish species, the increased death toll on the larvae and high energy cost of triggerfish parental-care in recent cooling conditions (T~22.0 °C) in Ghanaian waters were the discussed causes of the disappearance of the fish species. Therefore, the apparent disappearance of grey triggerfish in Ghanaian waters might have been caused by extreme temperatures experienced from 1987 to date.
