Observations on the behaviour of the grouper species Epinephelus guaza and E. alexandrinus (Serranidae)

Abstract

The two closely related grouper species Epine-phelus guaza (L) and Epinephelus alexandrinus (C et V) occur in high densities around the coast of Gozo. The greater part of this study was made on two neighbouring groups of fish at the mouth of Dwehra Bay on the West coast of Gozo. Special attention was paid to territorial organisation and associated behaviour, but various other aspects of the ecology of the two species were also studied. The results obtained reveal an unexpectedly loose territorial organisation (by comparison with Serranus scriba- Kirchshofer 1954) and considerable ecological differentiation between the two species. No systematic underwater observations on these groupers have yet come to our notice, though they have been well-known to divers and spearfishermen since the invention of the aqualung. Surface observations have been made on the ecology of Pacific species and the homing behaviour of Caribbean species; serranids were included in underwater observations on diurnal rhythms in California fishes