The monthly analysis of maturity stage frequency suggested that spawning of the grey triggerfish Balistes capriscus (Gmelin, 1788) is annual, total and occurs from November to February in the south of São Paulo State, Brazil. Size at first maturity is 169 mm for females and 200 mm for males. Condition factor estimated considering and disconsidering gonad weight (K and K') showed maximum values related to periods of higher frequency of females at advanced maturity stage. ΔK was higher in December, January and February, and was related to the maximum frequency of mature females. As K estimates the gonad condition it could be used as a maturity and breeding season index for this species. The gonadosomatic relation behaved the same as K values.
Balistes capriscus; grey triggerfish; reproduction; oocyte development; size at first maturity