ATTACHMENT OF LARVA, SURVIVAL AND GROWTH OF JUVENILE VARIANT SCALLOPS (Chlamys varia Linnaeus, 1758) IN CONTROLLED BREEDING IN ŠARINA DRAGA BAY — MOUTH OF THE KRKA RIVER

Abstract

Kontrolirani uzgoj male kapice (Chlamys varia Linnaeus, 1758) u Hrvatskoj ne postoji, a iz prirodnih se populacija izlovljava sezonski, sporadično i neorganizirano. Istraživanja indeksa kondicije adultnih malih kapica, prihvata ličinki, stupnja preživljenja i rasta juvenilnih školjkaša provedena su radi utvrđivanja mogućnosti njezina kontrolirana uzgoja. Rezultatima istraživanja utvrđeno je da mala kapica ima dualni tip mriješćenja, s primarnim maksimumom u proljeće (ožujak/svibanj) i sekundarnim u jesen (listopad). Najpovoljnije razdoblje za kolektiranje mlađi jest srpanj/rujan, a najpovoljnija dubina 2–10 m iznad morskoga dna. Najniži salinitet na kojem su utvrđeni prihvat i preživljenje ličinki jest oko 20 x 10–3, a uspješno kolektiranje moguće je uglavnom pri salinitetima višima od 30 x 10–3. U pokusnom su uzgoju male kapice, srednje veličine od 16,4±2,1 do 17,6±2,2 mm i srednje mase 0,95 do 1,35 g, nakon godinu dana postigle srednju veličinu od 42,7±3,2 do 47,5±3,0 mm i srednju masu od 12,1 do 17,5 g. Ukupna smrtnost za vrijeme istraživanja iznosila je od 25 do 57%.In Croatia, the capture of scallop (Chlamys varia Linnaeus, 17583) from natural populations are sporadic and unorganized, while there is no controlled cultivation of this species. To determine the possibility of the establishment of their commercial cultivation, the research comprehended the condition index of adults, larval attachment, juvenile survival and growth in Šarina draga Bay, in a locality with dense scallop populations. The changes of condition index shoved on main spawning season in spring (March–May) and second one, but less intensive, in autumn (October). According to results, the best season for juvenile collection is recommended the period from July to September at depths between 2 to 10 m, and salinities above 30 x 10–3. Low larval settlement at 2.5 m depth is surely result of salinity decrease by Krka river intensive fresh water inflow. Shellfish mean size from 16.4±2.1 to 17.6±2.2 mm and with a mean mass from 0.95 to 1.35 g reached mean size from 42.7±3.2 to 47.5±3.0 mm and mean mass from 12.1 to 17.5 g in one year. Total mortality during this study was ranged from 25 to 57%