Sastav sakupljenih ličinki riba i njihova prostorna grupiranost tijekom ljetnog razdoblja u sjevernom Egejskom moru

Fish larvae were collected in two surveys, carried out at the beginning of July 2002 and 2003 in Kavala Gulf (northern Aegean Sea) aimed at studying ichthyoplankton species assemblages and station groupings. The similarity dendrograms revealed the existence of four species assemblages associated with three station groups in 2002 and five species assemblages associated with four station groups in 2003. These groupings were confirmed by non-metric multidimensional scaling (NMDS) analysis. Analysis of similarity showed that the station groups were significantly different for 2002 (global R=0.748; P<0.001) and 2003 (global R=0.931; P<0.001). High dissimilarity between species assemblages as obtained from dendrograms and NMDS analyses was also recorded for 2002 (global R=0.834; P<0.001) and 2003 (global R=0.767; P<0.001). The assemblage structure was mainly determined by the most abundant and frequently occurring larvae, especially the European anchovy (Engraulis encrasicolus), and was largely influenced by the reproductive traits and spatial distribution of adult fish. Differences among station groupings were also determined by the spatial occurrence and abundance of each taxon.Riblje ličinke su prikupljene tijekom dvaju istraživanja koja su provedena početkom srpnja 2002. i 2003. godine u zaljevu Kavala (sjeverni dio Egejskog mora) s ciljem utvrđivanja strukture ribljih vrsta i postojanih populacija. Sličnost dendograma otkrila je postojanje četiri populacije povezane s tri skupine u 2002. godini i pet populacija povezanih s četiri stalne skupine u 2003. godini. Te skupine su potvrđene pomoću ne-metričke analize višedimenzionalnih skala (NMDS). Analiza je pokazala da su grupe stalnih populacija bile značajno različite za 2002. godinu (globalno R = 0,748; P <0,001) i 2003 (globalno R = 0,931; P <0,001). Visoki stupanj različitosti između grupacija dobivenih od dendograma i NMDS analize također je zabilježena za 2002. godinu (globalno, R = 0,834; P <0,001) i 2003 (globalno, R = 0,767; P <0,001). Skupna struktura uglavnom je bila određena prema najrasprostranjenijim i učestalim ličinkama, posebice brgljuna (Engraulis encrasicolus), te je uvelike bila pod utjecajem reprodukcijskih obilježja i prostornom raspodjelom odraslih riba. Razlike između utvrđenih grupacija također su određene s obzirom na prostorno pojavljivanje i brojnost svake svojte

Edad y crecimiento de la Alacha (Sardinella aurita) en el Mediterráneo noreste

The round sardinella, Sardinella aurita Valenciennes, 1847, was sampled monthly from commercial purse-seine vessels in Kavala Gulf (northern Aegean Sea, Greece) for two complete year cycles (September 2000-August 2002). Its maximum total length and age were 248 mm and 5 years respectively. The length-weight relationship was W=0.0062TL3.064 for males and W=0.0059TL3.084 for females. The marginal increment analysis on scales (n=1352) confirmed annulus formation during February-March, which coincided with the lowest sea surface temperature prevailing in the study area. The marginal increment ratio for ages 1, 2 and 3 was positively correlated with sea surface temperature (all r >0.4, P0.4, P< 0.05). Los parámetros de la ecuación de crecimiento de von Bertalanffy fueron L?=248.678 mm, K=0.509 años-1 y t0. La comparación de parámetros de crecimiento de la alacha para el Mediterráneo y las aguas del noroeste de África indican diferentes patrones de crecimiento entre las dos áreas

Summer distribution of fish larvae in northern Aegean Sea

Larval fish and hydrographic data were collected in Kavala Gulf (northern Aegean Sea) across a fine scale grid of 17 stations in two surveys, carried out in the beginning of July 2002 and 2003. Despite the different taxonomic resolution and excluding the unidentified larvae, 22 taxa were caught in 2002 and 27 in 2003. Seventeen taxa were present in both years' collections. A total of 833 larvae were collected during the two samplings. The adults of several larvae caught, although sometimes at very low concentrations, are species with high commercial value or represent a major proportion of the captured production of the northern Aegean Sea. The larvae of European anchovy (Engraulis encrasicolus) were most abundant in both years followed by the brown comber (Serranus hepatus), the gobies (Gobius sp.) and, only for 2003, round sardinella (Sardinella aurita). Maximum anchovy larval densities reached 4145/10 m(2) and 13852/10 m(2) in the 2002 and 2003 surveys, respectively. The spatial extent Of anchovy larvae was also high as they were collected at 12 stations in 2002 and at 15 in 2003. Besides water circulation, the spatial distribution of fish larvae was largely influenced by temperature, salinity and dissolved oxygen