Changes in the fish fauna composition of North-eastern Atlantic Ocean have been recorded based on the occurrence of warm affinity species. Individuals of Anthias anthias (Serranidae), Callanthias ruber (Callanthiidae), Dactylopterus volitans (Dactylopteridae), Halobatrachus didactylus (Batrachoididae), Seriola rivoliana (Carangidae), and Sphyraena sphyraena (Sphyraenidae) have been found along Galician waters, considered unusual species in this biogeographic transition zone. To classify them as seasonal migrant visitors or local spawners with settlement potential, gonad histological analyses were performed, showing that at least A. anthias, C. ruber, and H. didactylus were spawning capable when present in the area.
In turn, this work sheds light on the reproductive biology of these species, of which gonadal histological data were limited or non-existent. In fact, this study represents the first gonad histological analyses of A. anthias, C. ruber, and D. volitans. Our results described important traits of the reproductive strategies of the species analysed, having classified a C. ruber female as asynchronous batch spawner, and identifying lobular type and cystic spermatogonial testis in A. anthias, C. ruber, and H. didactylus males. Males of A. anthias and C. ruber presented potential histological evidence of protogyny with the description of melanomacrophage centres in both species.
Keywords: Exotic species · Gonadal histology · Protogyny · Reproductive biology · SW Europe · Unusual fish
