Abstract
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.
Highlights
The Norway lobster Nephrops norvegicus, Linnaeus 1758, is a common decapod crustacean inhabiting the muddy bottoms of the European continental shelves and slopes, at depths from 10 to 800 m
The proposed managing measures, such as the minimum landing size (MLS), total allowable catches (TACs) or maximum sustainable yield (MSY), are decided following biological scientific advices provided by the International Council for the Exploration of the Sea (ICES) [3,5,6]
Populations of Nephrops are known to differ in terms of distribution, density, or growth rates, even in small spatial scales
Summary
The Norway lobster Nephrops norvegicus, Linnaeus 1758, (hereafter referred to as “Nephrops”) is a common decapod crustacean inhabiting the muddy bottoms of the European continental shelves and slopes, at depths from 10 to 800 m. It is found throughout the northeast Atlantic and in the western Mediterranean, the Adriatic, and the Aegean seas, with its distribution being limited by the extent of suitable muddy sediment in which animals construct their burrows [1]. Across Europe, it is considered an important target species in 34 Functional Management Units (FUs), with the UK and Ireland sharing the majority of landings from the North Atlantic stocks, followed by France, Iceland, Denmark, and Sweden [3]. Fisheries management should not be based on just recent studies, but rather on long time series data in order to better understand the temporal changes in species abundance, distribution and biology [8]
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