Epibionts in artificial collectors / Epibiontes en colectores artificiales

Artificial collectors are tools that explain the settlement dynamics of marine invertebrates. What is known about these in the Caribbean is very limited. In order to identify and quantify the diversity of epibionts in relation to depth, between December, 2015 and August, 2016, cylindrical collectors were suspended on a long line at varying depths. At each experimental depth, bimonthly temperature, chlorophyll a, and total seston records were obtained. 7,078 individuals belonging to five phyla were counted: Chordata, Echinodermata, Arthropoda, and Mollusca. The mollusks, mainly bivalves, were the most abundant, represented by: Pinctada imbricata, Pteria colymbus, and Crassotrea rhizophorae. The recruitment of organisms showed significant changes over time, with different fixation patterns. Abundance, wealth, and diversity, in each of the experimental depths were modulated by the temperature and phytoplankton biomass and the seston. The collectors, regardless of depth and time, acted as artificial habitats, reflecting the variety of benthic organisms, mainly mollusks, that naturally share the different environments that surround the southern coast of the Gulf of Cariaco, which could be a dynamic observed in the southeast Caribbean. The Gulf of Cariaco is an important ecosystem service due to the larval supply it provides to the environment, related to the fertility of its waters.

Reproductive biology of the rayed pearl oyster (Pinctada imbricata radiata, Leach 1814) in Izmir Bay

The present study was carried out to determine gonadal stages and quality of pearl oyster meat (Pinctada imbricata radiata, Leach, 1814) in Izmir Bay (Turkey). Pearl oyster samples were collected from the study area at a depth of ~5 m between February 2013 and January 2014. The highest and lowest temperature was measured in July and January as 27°C and 14.2°C, respectively. The maximum chlorophyll a value of 4.640 μg l−1 was calculated in May and the lowest value of 1.009 μg l−1 was recorded in April. Individuals reached their first maturity in April. Spawning activity was observed from June to September and the gonad index (GI) was at the highest level during those months. The development was observed from April to February. The overall female to male ratio was 1.32:1 (p < 0.05) and it did not affect the GI (p > 0.05). There is a strong positive correlation between the GI and temperature (p < 0.05). The highest condition index (CI) was recorded in May as 12.31 ± 0.51, whereas the lowest one in January as 7.37 ± 0.22. As a result, this study revealed that the pearl oyster population in the region is characterized by high reproductive activity, especially during the summer months.

GROWTH AND SURVIVAL OF SPAT, JUVENILES AND ADULT AKOYA PEARL OYSTER PINCTADA IMBRICATA FUCATA (GOULD, 1850) IN DIFFERENT REARING CONDITIONS AND STOCKING DENSITIES

Growth trials were conducted using hatchery produced spat of Pinctada imbricata fucata (Gould, 1850) having average dorso-ventral measurement (DVM) of 3.99 mm, hinge length (HL) 3.94 mm, thickness (THK) 1.25 mm and weight (WGT) 0.008 g. The first experiment was a comparative growth assessment of spat grown in one ton FRP tanks in the hatchery and with that of spat reared in micron meshed cages under open sea conditions for a period of three months. During the third month, spats grown in micron meshed cages showed growth increments of 7.83 mm (DVM), 4.86 mm (HL), 1.61 mm (THK) and 0.192 g (WGT) whereas those grown in FRP tanks grew only by 0.95 mm (DVM), 0.5 mm (HL), 0.46 mm (THK) and 0.004 g (WGT) indicating faster growth in open sea conditions. Second experiment was conducted to elucidate the effect of stocking density on the growth and survival of juveniles reared in plastic baskets at different stocking densities viz., 200 (0.03 nos. cm-3) 300 (0.049 nos. cm-3), 400 (0.065 nos. cm-3), 500 (0.08 nos. cm-3), 600 (0.098 nos. cm-3), 700 (0.11 nos. cm-3), 800 (0.13 nos. cm-3), 900 (0.14 nos. cm-3) and 1000 (0.16 nos. cm-3) numbers per basket. Results indicated that P. imbricata fucata juveniles can be grown at stocking densities of up to 400 per basket for a period of five months with 90% survival without much reduction in growth. Third experiment was conducted on the growth of P. imbricata fucata subadults in box cages at different stocking densities viz., 200 (0.006 nos. cm-3), 300 (0.01 nos. cm-3), 400 (0.013 nos. cm-3), 500 (0.016 nos. cm-3), 600 (0.02 nos. cm-3), 700 (0.023 nos. cm-3), 800 (0.026 nos. cm-3), 900 (0.03 nos. cm-3) and 1000 (nos. cm-3) numbers per cage. Survival rates ranged from 98.5 to 98.6% at stocking densities up to 400 per cage during the fifth month without any significant variation in the DVM, HL and THK of oysters.