The Atlanto-Mediterranean holothurian Holothuria tubulosa is among the conspicuous benthic invertebrates in the shallow sublittoral zone. It is an edible species, harvested at the Aegean Sea and utilized as fishing bait. Considering the lack of information for the Aegean populations, a one-year survey, based on monthly or semimonthly samples, was carried out focusing on population structure, allometric relationships and reproductive status of H. tubulosa stocks in Pagasitikos Gulf. Population density varied around 9.93 individuals/100 m². This value was rather low compared with other studied Mediterranean populations of the species, possibly due to the scarcity of seagrass meadows in the area studied. All measured biometric characters showed high plasticity, and all the examined morphometric relationships followed negative allometry indicating a change to the shape of the animal's body as it grows. Holothurians’ length was a moderate predictor of biomass since r values reached 60%; in contrast a very strong relation was observed between drained and gutted weight. Size–frequency distribution analysis was unimodal with the exception of spring where a second mode of larger sized individuals appeared. The gonadosomatic index showed a single spawning season per year, in late summer; accordingly the reproductive cycle of the species showed a clear annual pattern which was highly correlated with the seasonal variations of temperature.

The reproductive cycle of the traditionally exploited sea cucumber Holothuria tubulosa was investigated in the Pagasitikos Gulf (39 degrees 18'457 '' N, 23 degrees 05'869 '' E) from June 2007 to July 2008. The study examined the microscopic characteristics of the gonads and was based on maturity index (MI) and oocytes' size-frequency distribution. The reproductive cycle was found to be synchronous between sexes, following an annual pattern. The minimum MI values were recorded in December and January, marking the onset of the reproductive cycle. During the spring, MI increased due to gamete development and proliferation. Mature specimens were prominent in summer while spawning occurred between July and September. The maximum MI values were recorded in mid-autumn, when most specimens were at the postspawning stage. The oocytes' size-frequency distribution showed analogous seasonal variability. The present findings are crucial for establishing an efficient management strategy for this commercial and ecosystem-engineering species, since its exploitation in Greek waters has not been under official control for more than a century. The authors propose a seasonal ban on the exploitation of the species from July to September and a minimum individual drained weight limit of 250 g

Acute toxicity and inhibition on growth of Artemia franciscana nauplii (Instar I-II) after exposure to the reference toxicants bisphenol a (BPA) and sodium dodecyl sulfate (SDS) were studied. LC₅₀ values were calculated and differences in body growth were recorded after 24, 48, and 72 h of exposure to the toxicants. The results indicated that BPA had lower toxicity than SDS. Development of the nauplii was clearly influenced by duration of exposure. Growth inhibition was detected for both toxicants. Abnormal growth of the central eye of several Artemia nauplii after 72 h of exposure to BPA was also detected. Our results indicate that growth inhibition could be used as a valid endpoint for toxicity studies.

The black sea urchin (Arbacia lixula, Linnaeus, 1758) is a non-edible marine echinoderm of high ecological importance with the potential to affect marine ecological communities. A. lixula were sampled monthly for one year from the supralittoral fringe at two locations in the Pagasitikos Gulf, in the north-western Aegean Sea. Morphometric characteristics exhibited significant spatiotemporal variation. The population in closer proximity to treated sewage effluent outflow exhibited significantly higher biometric relationships resulting in possible improved physiological conditions. Spatial distribution exhibited a clumped pattern of dispersion, consisting of predominantly six age classes. The dominant cohort was the four-year age class, comprising 31.2% of the total population. Significant negative allometric relationships were exhibited between all morphometric characteristics. The maximum approximate age of the total A. lixula population was estimated at 15.27 years. The von Bertalanffy growth equation for the entire population was estimated as: test diameter = $62.881\times \left(1-e^{-0.196\times \left(Age+1.147\right)}\right)$. The gonadosomatic index indicated a seasonal cycle with a peak in late spring. The approximate age of sexual maturity was estimated at 4.45 years. We observed a significantly higher number of females than expected at the site in closer proximity to the treated sewage effluents (32% of total female number).

Norway lobster (Nephrops norvegicus) is one of the most valuable shellfish resources in the Mediterranean and the northeast Atlantic. Sustainable management of its fishery require long-term scientific monitoring of its stocks. Population dynamics, fishery, and exploitation status of the Norway lobster were studied over a long time series (between 2008 and 2014) in a semi enclosed gulf in Easter Mediterranean (Pagasitikos Gulf). Sampling was carried out using a commercial bottom trawl with a codend mesh size of 28 mm in three different regions within the Gulf. Sex was identified macroscopically and all individuals were measured and weighed. Growth and Age groups were investigated by analysis of length–frequency distributions of the Carapace length (CL) for both sexes. Fishing, Natural and Total Mortality, along with Exploitation rate of the total stock were estimated by the FiSAT software package. Females were further examined and classified based on their maturity stage and the size at onset of sexual maturity was estimated by Probit analysis. Temporal differences in mean CL were detected for both sexes, with a tendency of lower values each year, along with a respective increase in Fishing Mortality and Exploitation Rate, indicating the effects of fishing pressure over the population. Size at onset of sexual maturity was estimated at 32.6 mm, higher than the official mesh sizes for creels (28 mm) and gillnets (26 mm). According to the analyses, the local Norway lobster stock is over-exploited, which should be taken under consideration by the regional policy makers.