Aspects of the reproductive biology of the toadfish, Halobatrachus didactylus (Schneider, 1801) (Pisces : Batrachoididae)

The biology of Halobatrachus didactylus has received special attention duri ng recent years because of its use as an experimental species in toxicology and cardiology experiments. The object of the present work is to supply ba sic information about the reproductive biology of this species. Samples wer e collected in Cadiz Bay between February 1999 and March 2000. A total of 9 01 specimens (440 females and 461 males) were examined. Sex ratio did not d iffer from the theoretical 1:1, except in May 1999, and February 2000. Mini mum size at maturity was 191 mm total length for females and 160 mm total l ength for males. Approximately 50 % of the population matured at 262 mm for females and 302 mm for males. The spawning season extends from March to Au gust, with a peak in May-June. Fecundity ranged from 227 to 1233 eggs/femal e, and was related to body length and weight. Length-weight relationship fo r the sexes differed, and showed positive allometry. The condition factor s howed a minimum in the spawning season, which is interpreted as the result of mobilization of somatic energy reserves needed for reproductive developm ent, and/or the use of reserves stored in the body as a source of energy in spawned fish, influenced by reduced feeding during this period.