of C. linearis in the North Eastern Atlantic. Also the temperate species Entelurus aequoreus is common along the European coast and around the Azores. All specimens of both temperate species were caught during autumn. A southward transport must have occurred, though the autumn season is known as a time of northward transport of all water masses (JOHN et al. 2004a; KNOLL et al. 2002). This can be explained by JOHN et al. (2004a) since no AAIW northward flow was present in autumn 1997 and the SW and NACW had a clear southward geostrophic net transport during autumn 1997, when those specimens occurred. A southward transport is also most likely since C. linearis was recorded around Madeira for the first time already in 1995 (WIRTZ et al. 2007). TORTONESE (1984) noted that Microichthys coccoi is only known from the strait of Messina, but he pointed out, that some young Epigonus telescopus (RISSO, 1810). from the North Atlantic could have been confused with M. coccoi. So, it might be that M. coccoi is more common in the North Atlantic, than has been observed up to now. If M. coccoi really would occur only in the Mediterranean Sea, a passive drift out of the Mediterranean Sea by outflowing water is most likely.
4.3. Occurrence and distribution patterns 4.3.1.Vertical spatial occurrence and distribution RODRÍGUEZ et al. (2006) noted that the vertical distribution does not depend on the thermocline and the associated phytoplankton peak, but is more species-specific and related to other environmental conditions. Regarding the depth distribution of different communities the common separation of realms into neritic, epi- and mesopelagic is not sufficient. Nevertheless, there is a trend for the communities of the epipelagic zone to consist of neritic as well as mesopelagic larvae. At this stratum an exchange between the neritic and oceanic species takes place. For that reason, the diversity (Shannon and Simpson’s Index) and number of species are highest in the upper 150 m (although the neritic realm is included here) and decreases depending on the water masses in the present study, although a fine scale study on the vertical distribution of larvae by RODRÍGUEZ et al. (2006) showed, that larvae do not occur directly in the surface stratum but within 20 – 66 m depth, but the diversity was highest in 50 – 66 m depth. The species number is also highest in the most upper layer of the water collumn. This is because larvae of all oceanic species favour this stratum, especially the most divers family of myctophids. They mainly inhabit the upper 100 m and no specimens were found deeper than 150 m (SASSA et al. 2004). Allowedly, this relation is poor since no simultaneous measurements of the hydrographic situation were done and stratum information were taken from the literature. Anyway, the depth and hydrographic situation e.g. water masses should be considered and related to the fish larval distribution in future studies. Within the neritic realm, a dominance effect occurs because of the high number of Gobiidae and Engraulidae. Evenness differs significantly between the neritic and the mesopelagic realm. In the mesopelagic realm few species and the lowest numbers of individuals were found, but they were evenly distributed. Though most species inhabit the neritic and epipelagic realms, the evenness of the surface waters including the neritic realm is significantly lower compared to deeper layers, which is also caused by the engraulids and gobies. Anyway, the diversity (Shannon and Simpson’s Index) is highest in the epipelagic zone, since no dominance effect occurs and the community consists of neritic as well as oceanic species. The region, where this exchange takes place is in the Islands’ wakes and eddies as clearly seen in Figure 22 – Figure 23. Looking at the diversity (Shannon and Simpson’s Index) and especially at the species number around the single Islands, the main exchange happens southeast of Fuerteventura. Here, in the epipelagic realm close to the slope, productivity seems to be the highes among all areas of the archipelago which have been investigated so far.
Inf. Téc. Inst. Canario Cienc. Mar. n°13
Published on Mar 26, 2013
Published on Mar 26, 2013
Technical report consisting on a comprehensive annotated larvae taxa list with the most important taxonomic characters of this region