Trap Fishery and Reproductive Biology of the Whitespotted Rabbitfish Siganus sutor (Siganidae), within the Dar es Salaam Marine Reserves, Tanzania

Abstract

Fish samples and catch data were collected monthly from traditional basket fish traps set on reefs within the Dares Salaam Marine Reserves (DMRs) to evaluate trap catch dynamics and reproductive biology of the rabbit fish Siganus sutor (Valenciennes 1835). Trap catch composition was 85% rabbitfishes by weight with a mean ([plus or minus] SE) catch per unit effort (CPUE) of 2.8 [plus or minus] 0.1 kg trap-1 day-1 during a fishing season, which lasted between September 2004 and May 2005. CPUE did not differ significantly with lunar cycle, but exhibited a spatial variation, the highest being from Fungu Yasini Marine Reserve, which is further from shore. The spawning season of S. sutor is protracted, lasting between October and May, peaking in March. Size at first sexual maturity was 217.1 and 227.7 mm TL for male and female S. sutor, respectively. The species exhibits a size-dependent sex ratio, with a preponderance of females at larger sizes. The species shows high fecundity at a maximum of 1,300,400 oocytes for 396 mm TL female. Average ([plus or minus] SE) total fecundity was 627,052 [plus or minus] 78,886 oocytes per female of 266 to 396 mm TL. It is proposed that beach seines be eliminated from the marine reserves and regulated trap fishery be allowed as a way to facilitate sustainable exploitation of the rabbitfishes and other reef fishes in the DMRs.