Microhabitat preferences and depth distribution of combtooth blennies (Blenniidae) in the Gulf of Trieste (North Adriatic Sea)

Until now there has been little documentation about the habitat and microhabitat choices of small benthic fishes in the Mediterranean Sea. Among these fish families, the scientific community has shown more interest in the last decades in combtooth blennies (family Blenniidae), bottom-dwellers that occur in coastal waters (Patzner 1985; Koppel 1988; Pallaoro & Števčić 1989; Illich & Kotrschal 1990; Abel 1993; Lipej & Orlando-Bonaca 2006). Nowhere else are these blennies as abundant and diverse as in the Mediterranean Sea, where 19 species have been found (Almada et al. 2001). Fifteen species live in the Gulf of Trieste (North Adriatic Sea) (Lipej & Richter 1999; Lipej et al. 2005). As they are without economic value and because they inhabit hard bottoms where it is impossible to collect samples with trawls, little was known only 30 years ago. Knowledge about these benthic fish species has recently been increasing by the use of non-destructive visual census methods, aided by SCUBA diving (Koppel 1988; Kotrschal 1988; Pallaoro 1989; Kovačić 2002; Lipej & Orlando-Bonaca 2006). The influence of habitat selection on depth distribution of some species has been previously studied (Gibson 1969, 1982; Zander 1969; Pallaoro 1989; Illich & Kotrschal 1990; Nieder 1992, 2000; Macpherson 1994; Zander et al. 1999). However, in the study of the factors affecting habitat occupancy and depth distribution of blennies there are still many open questions. The study was aimed at testing the null hypothesis that there are no differences in microhabitat preferences between different blennies in the coastal waters of the Gulf of Trieste. As a working hypothesis, it was assumed that differences between species exist in microhabitat preferences and water depth utilization. This study was conducted by SCUBA diving during spring and summer months (May–October). It is a period when territorial blenny males prepare nests. Many species