Composition and diversity of ichthyoplankton in the Boka Kotorska Bay (South Adriatic Sea)

Variation in the diversity of ichthyoplankton was analyzed from samples collected during threeyear cycle in Boka Kotorska Bay. Samples were collected using Calvet (modified PairOVET) plankton net at 18 stations, from July 2006 through January 2009. Families with most numerous species were Engraulidae, Sparidae and Labridae. Investigation shows dominance of anchovy (Engraulis encrasicolus), Mediterranean rainbow wrasse (Coris julis) and annular sea bream (Diplodus annularis) during the summer. During the winter, dominant species were sardine (Sardina pilchardus) and Atlantic mackerel (Scomber scombrus), while during the spring dominant species were anchovy, annular sea bream and white sea bream (Diplodus sargus). Spawning of most pelagic fish species in Adriatic Sea starts in spring, and progress during spring and summer months. Therefore, the highest number of species was found in these months, while the lowest number of species was during autumn and winter surveys. Eggs and larval stages of 35 species was determined, while the diversity analysis showed a significant degree of diversity in certain stations where the sea currents were probably the strongest. Diversity of ichthyoplankton communities was analyzed applying two diversity indices: Shannon index (H’) and Simpson index (D). Diversity analysis was performed for each of the 18 investigated stations during the tree-year research, while influence of environmental factors on presence of some ichthyoplankton species by seasons was tested with Canonical Correspondence Analyses (CCA).
Kolebanja u raznolikosti ihtioplanktona analizirana su na uzorcima prikupljenim tijekom tri godine u Bokokotorskom zaljevu. Uzorci su prikupljeni pomoću Calvet (modificirani PairOVET) planktonske mreže na 18 postaja, od srpnja 2006. do siječnja 2009. Najbrojnije su bile obitelji vrsta Engraulidae, Sparidae i Labridae. Istraživanje pokazuje dominaciju inćuna (Engraulis encrasicolus ),kneza (Coris julis) i špara (Diplodus annularis) tijekom ljeta. Tijekom zime, prevladavajuće vrste su bile srdela (Sardina pilchardus) i skuša ( Scomber scombrus), dok su u proljeće prevladavajuće vrste bili inćun i šarag (Diplodus sargus). Mrijest većine vrsta riba u Jadranu počinje u proljeće, a progresivni napredak se odvija tijekom proljetnih i ljetnih mjeseci. Dakle, najveći broj vrsta je pronađen u proljetnim i ljetnim mjesecima, dok je najmanji broj vrsta pronađen tijekom jesenskih i zimskih istraživanja. Tijekom istraživanja pronađeni su jaja i ličinke 35 vrsta, dok je analiza pokazala značajan stupanj raznolikosti na pojedinim postaja gdje su morske struje vjerojatno najjače. Raznolikost ihtioplanktonske zajednice je analizirana primjenjujući dva indeksa raznolikosti: Shannon indeks (H’) i Simpson indeks (D). Analiza raznolikosti je provedena za svaku od 18 istraživanih postaja tijekom trogodišnjih istraživanja, dok je utjecaj ekoloških čimbenika na prisutnost nekih vrsta po sezonama bio testirana primjenom CCA analize (Canonical Correspondence Analyses).