Growth and reproduction of the dolphinfish (Coryphaena equiselis and Coryphaena hippurus) in the Canary Islands, Central-East Atlantic (preliminary results)

Abstract

The size, growth and spawning characteristics of pompano dolphin (N=150) and common dolphinfish (N=36)caught off the Canary Islands between May and September 1995 and between July and September 1996 were examined.Fork length (FL) of pompano dolphin was in the range 28.3-62.8 cm. In 1995, the mean length increased significantly fromJune to September. However, in 1996, the mean length was significantly larger in July than in September. The overalllength-weight relationship was W=0.0287*FL2.774(r=0.97), while these relationships by sex were as follows:W=0.031*FL2.758(r=0.98) and W=0.0282*FL2.776(r=0.97), for males and females respectively. Spawning takes place at thebeginning of the Summer (June-July). All the individuals obtained showed developing gonads, but females showed a high-er gonadosomatic index (GSI) than males. The highest GSI values were obtained in June (x- =3.10±1.73), and decreased pro-gressively towards the end of the season (September), when the average of this index was x- = 1.86±0.87. Similarly, the con-dition index decreased significantly from June to September. The proportion of females was always significantly higher thanmales, except in July 1996 when it was 1:1. There was a high correspondence between growth rates determined by annuliscale interpretation and modal progression analysis. According to scale annuli interpretation, the individuals caught showedmore than five age classes. However, there are doubts about age assignation from scales. Fork length of common dolphin-fish was in the range of 76.5-103.0 cm. The length-weight relationships obtained for all the specimens caught wasW=0.00095FL3.527(r=0.96), while these relationships by sex were as follows: W=0.00398FL3.222(r=0.94) andW=0.01656FL2.873(r=0.91), for males and females respectively. Spawning probably takes place at the beginning of the Sum-mer. All the individuals obtained showed developing gonads, although the GSI of females were higher than males. The high-est GSI values were obtained in June (x- =5.50±2.17). In the same way, the condition index decreased from May to June. Theproportion of females was always slightly higher than males (1:1.4), but the ratio was not significantly different from 1:1.