Differences between demersal fisheries discards: high and low productivity zones of the Northwestern Mediterranean Sea

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Tag shedding estimation in Palinurus elephas (Fabricius, 1787)

In this paper a numerical method for tag shedding calculation from double tagging data was used to estimate the tag loss rate in Palinurus elephas from capture-mark-recapture experiments. Four consecutive experimental surveys during years 1999-2002 inside the Columbretes islands marine reserve (CIMR) were carried out and the captured spiny lobsters were dorso-laterally double-tagged with T-bar anchor tags on both sides between the first and second abdominal segments. The recaptures during the following years (2000-2008) were recorded and the evolution of the proportion of single- and double-tagged specimens was analysed. The immediate tag loss produced after tagging could not be accurately modelled, but in view of the results is believed to be low. The probability of tag loss per year was estimated in 6% (sexes combined). The factors causing this tag loss and the repercussion of this rates of shedding on further studies are examine

Double tagging experiments and tag loss in Palinurus elephas

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Isotopic tissue fractionation in captive and wild lobsters Palinurus elephas (Fabricius, 1787)

Isotopic fractionation δ13C and for δ15N of the spiny lobster Palinurus elephas has been tested in four tissues: tail and leg muscle, telson and hemolymph. Comparison of tissue fractionation factors among tissues in two groups of lobsters, captive (controlled diet) and wild, show lower intra-individual variability in captive than in wild individuals. Statistical analysis (PERMANOVA) was performed to check for significant differences in δ13C and δ15N isotopic signatures between tissues and treatments. Results show significant differences in the δ13C and δ15N isotopic composition among the four tissues analyzed. Legs are the most enriched tissue in δ15N, followed by muscle, hemolymph and telson in both captive and wild specimens. For δ13C the sequence is muscle > legs> hemolymph ~ telson. The fractionation or enrichment factor for δ 13C is 0.87‰ and 1.17‰ and for δ15N 1.99‰ and 2.38‰, in captive and wild lobsters respectively. Leg muscle presents the lowest variability at isotopic level for N and telson for C. Telson presents differences for N and C in both captive and wild lobsters (Mann-U Whitney p<0.05). Hemolymph and leg only present statistical differences for N between captive and wild individuals. In the first study of tissue isotopic fractioning of a spiny lobster species we conclude that leg muscle is the best tissue for studying P. elephas trophic dynamics applying non-invasive technique

First V-notching experiment in the spiny lobster Palinurus elephas

V-notching tagging has been practiced for decades in juveniles and ovigerous females of the clawed lobsters Homarus americanus and H. gammarus as an effective conservation strategy in several European and US fisheries. For the first time a V-notch experimental study was conducted with the spiny lobster Palinurus elephas with the aims of: 1) assess survival of notched versus unnotched lobsters, 2) assess differences in the incidence of shell disease of notched and unnotched lobsters, and 3) assess the rate of notch loss (tag retention) with respect to molt frequency. A total of 36 wild young adults were housed in a tank of 10000 litres separated in three replicates of 12 lobsters each one. Half of individuals of each replicate were marked with a v-notch (side 1 cm long). Tank environmental conditions (temperature, salinity and dissolved oxygen) were controlled to mimic conditions in the wild. The experiment lasted 20 months. There were no significant differences in survival or health conditions of notched and unnotched specimens. After 15 months, all the indivudals had completed two molts and five of them have undergone the third one. After the second molt on average 25% of the notched area has been overgrown and lobsters with the third molt have overgrown 45% of the notched area. The performance of area, width and height of the V-notch tab for regulatory purposes are discusse

Will we see you again? Population evaluation of Palinurus elephas inside a marine reserve from Capture-Mark-Recapture data

To achieve an effective management of the marine exploited populations it is necessary to understand their dynamics and the processes driving short- and long-term changes. Key population parameters such as survival and movement can be estimated by means of capture-mark-recapture studies, based on the capture, tagging and re-encounter of the individuals at later times. The Cormack-Jolly-Seber model, which assesses the apparent survival i and the recapture rate pi of a population conditional on first capture, was applied to European spiny lobster Palinurus elephas data from the Columbretes islands marine reserve to evaluate the evolution of this population after closure to fishing over. Particularly strong winter conditions were reported for some years during the period of study whcih were reflected as an increase in the estimate of the encounter probability and a decrease in their survival rate. P. elephas showed a relatively high plasticity against short-term environmental effects, with the apparent survival quickly returning to pre-storm levels. Also a slight increase in survival was identified for this protected population over time. These preliminary results are discussed in terms of the factors affecting the dynamics of this population and the implications for the management of this exploited stoc