Evaluating sea cucumbers as extractive species for benthic bioremediation in mussel farms

Filter-feeding mussels blend suspended particles into faeces and pseudo-faeces enhancing organic matter flows between the water column and the bottom, and strengthening benthic-pelagic coupling. Inside operating farms, high bivalve densities in relatively confined areas result in an elevated rate of organic sinking to the seabed, which may cause a localized impact in the immediate surrounding. Deposit-feeding sea cucumbers are potentially optimal candidates to bioremediate mussel organic waste, due to their ability to process organic-enriched sediments impacted by aquaculture waste. However, although the feasibility of this polyculture has been investigated for a few Indo-Pacific species, little is known about Atlanto-Mediterranean species. Hence, for the first time, in the present study, we conducted a comparative investigation on the suitability of different Mediterranean sea cucumber species, to be reared in Integrated Multitrophic Aquaculture (IMTA) with mussels. A pilotscale experiment was accomplished operating within a mussel farm where two sea cucumbers species, Holothuria tubulosa and Holothuria polii, were caged beneath the long-line mussel farm of Mytilus galloprovincialis. After four months, H. tubulosa showed high survivorship (94%) and positive somatic growth (6.07%); conversely H. polii showed negative growth (− 25.37%), although 92% of specimens survived. Furthermore, sea cucumber growth was size-dependent. In fact, smaller individuals, independently from the species, grew significantly faster than larger ones. These results evidenced a clear difference in the suitability of the two sea cucumber species for IMTA with M. galloprovincialis, probably due to their different trophic ecology (feeding specialization on different microhabitats, i.e. different sediment layers). Specifically, H. tubulosa seems to be an optimal candidate as extractive species both for polycultures production and waste bioremediation in M. galloprovincialis operating farms

Improving the reproductive yield of Black Sea Salmon (Salmo labrax PALLAS, 1814) with a selective breeding program

This study aimed to improve some culture characteristics of Black Sea salmon (Salmo labrax) culture generations through a classical selective breeding program. Thus, the success of the applied program was examined by comparing the reproduction time and proportional distribution of the wild broodstock (F-0) individuals with the F-1, F-2, F-3 and F-4 generation broodstocks adapted to the culture conditions. According to the results, gamete uptake from the new generations occurred between October and February. The highest egg uptake was determined for all generations in December. While the difference between wild (F-0) broodstock and F-1, F-2, F-3, and F-4 generations was statistically significant in favor of new generations (P<0.05), the difference was insignificant between hatchery origin-new generations. Mean egg diameters were low in F-2 and F-3 generations, and F-0, F-1 and F-4 generations were found to be higher than the others (P<0.05). It was calculated that the fertilization rate was higher in F-3 and F-4 generations, similar in F-1 and F-2 generations, and lower in F-0 generation than the others (P<0.05) at the end of the study. Through the selection program, it was determined that the adaptation of the species to the culture conditions improved, the reaction to human activities declined, and homogeneous distribution in tanks/ponds was relatively achieved from the F-2 generations. As a result, it has been determined that F-4 generation broodstock have higher culture performance than other generations. Producers of this species should use F-4 broodstock for efficient and economical production.General Directorate of Agricultural Research and Policies (TA-GEM) , Ministry of Agriculture and Forestry, Republic of Turkiye TAGEM/HAYSUD/2001/07/01/20 TAGEM/HAYSUD/2006/09/03/02 TAGEM/HAYSUD/2011/09/01/0