Abstract
Spat supply for mussel farming in Morocco is essentially based on seed capture and collection from natural beds. However, natural irregularity recruitment in exploited areas and encountered difficulties during spat collection operations have led to develop and improve reproduction techniques under controlled conditions in hatcheries. The present study focused on the larvae phase aiming at assessing growth rate varies between different development stages. Trocophore larva stage had a size of 63.25 μm and reached the pedivilegere stage with a size of 272.56 μm in 18 culture days. Length growth was more significant than width growth for both H-batch and T-batch. For instance, larvae grew in terms of length quickly in H-batch than T-batch (11.10± 1.30 and 9.67 ± 1.17 μm day-1), and the same pattern was observed for T-batch larvae. Inversely, the total biomass consumed was higher during T-batch larvae rearing than H-batch ones. In contrast, the effect of feeding on growth was observed more significantly for H-batch larvae (t=7.55, df=23, p<0.001) than T-batch ones (t=4.13, df=23, p<0.001). However, the specific feeding effect was revealed higher for I. galbana for both batches rather than C. calcitrans and T. suecica. However, the larvae growth reduction is linked to the beginning of tissue synthesis.
Highlights
Shellfish farming is mainly based on the availability of wild spat [1, 2]
During the early larvae stages, only I. galbana and C. calcitrans were supplied as food based on 1,300 cells/larvae and 700 cells/larvae) respectively
In terms of specific consumption, T. suecica is more consumed in biomass in both H-batch and Tail batch (T-batch) with values of 2431.85 ng Larvae-1 and 2970.43 ng Larvae-1 followed by I. galbana with 1226.47 ng Larvae1 and 1290.75 ng Larvae-1, respectively
Summary
Shellfish farming is mainly based on the availability of wild spat [1, 2]. Optimization in bivalve hatchery productivity requires, among others, assessment of multi-species algae as feeding diets to enhance growth and survival during the larval phase. Many studies have been carried out on bivalves to understand and improve the spat production process in this context. Such studies have successfully optimized conditions for the growth and survival of bivalve larvae in hatcheries [6, 7], while other studies have been based on physiological parameters [8]. Microalgae culture is so influential because it is the only feed source for bivalve larvae [11]. Some commonly used micro-algae species as mussel larvae feed include Isochrysis galbana, Isochrysis galbana Tahiti strain, Chaetoceros calcitrans, C. muelleri, C. gracilis, Tetraselmis suecica, Skeletonemacostatum, Rhodomonas lentil, Pavlova lutheri, and P salina [15, 16]
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