Fish Response to Multiple Anthropogenic Stressors in Mediterranean Coastal Lagoons: A Comparative Study of the Role of Different Management Strategies

Transitional waters are among the most productive ecosystems of the world and their biotic communities show high diversity and complex mechanisms of self-regulation that provide valuable ecosystem services and societal goods and benefits. In this work a comparison of the fish assemblages of three non-tidal Mediterranean coastal lagoons is carried out in order to evaluate the impacts of alternative management strategies. The anthropogenic pressures acting on the lagoons were quantified by means of categorical indicators, while the characteristics of the fish assemblages were summarized in multi-metric indices (MMIs). Two MMIs were developed using data collected with a beach seine net and with fyke nets, following an empirical approach that selects, from a pool of 73 metrics, the combination that maximizes the MMI/pressure relationship. The two MMIs include four metrics each, most of which are based on feeding mode functional guilds and habitat use functional guilds, and they are sensitive to anthropogenic pressures. The human activities directly or indirectly affecting water quality are the ones that most influence the fish assemblage, while the presence of artisanal fisheries, a typical and relevant resource use in these lagoons, seems to play a beneficial role. Lagoon fisheries management relies on the maintenance of infrastructures that guarantee the hydraulic functioning of the lagoon, thus ensuring exchanges with the adjacent coastal sea, and therefore indirectly contributing to the habitat quality

Fishery-Induced Selection for Slow Somatic Growth in European Eel

Both theoretical and experimental studies have shown that fishing mortality can induce adaptive responses in body growth rates of fishes in the opposite direction of natural selection. We compared body growth rates in European eel (Anguilla anguilla) from three Mediterranean stocks subject to different fishing pressure. Results are consistent with the hypotheses that i) fast-growing individuals are more likely to survive until sexual maturity than slow-growing ones under natural conditions (no fishing) and ii) fishing can select for slow-growing individuals by removing fast-growing ones. Although the possibility of human-induced evolution seems remote for a panmictic species like such as the European eel, further research is desirable to assess the implications of the intensive exploitation on this critically endangered fish

Il caso dell’anguilla europea, tra gestione e conservazione.

The European eel, Anguilla anguilla L., is recognised today as an international marine species and a shared resource among European and Mediterranean countries. For this species, major problems exist in relation to a continent-wide decline in recruitment observed in the course of the last decades, and to a contraction in adult eel capture fisheries. In relation to this situation, debate on the possible measures to protect the European eel stock is topical at the present moment, also in relation to a series of steps undertaken by the European Community

Acclimation trial of Mugil cephalus juveniles to freshwater: morphological and biochemical aspects

Acclimation trials of Mugil cephalus juveniles (SL = mean 28.05, sd = 3.54 mm) were performed by means of a gradual transfer to freshwater in 48 h. The adaptation capabilities of M. cephalus were evaluated using descriptors such as tissue osmolality, chloride cell number, Na+-K+ ATPase activity and morphological aspects of oesophagus and gills. The high survival rate and tissue osmolality regulation demonstrate the adaptation ability of striped mullet of this size. Chloride cell number and osmolality proved to be good markers of functional adaptation. The morphological and biochemical aspects of oesophagus and gills in juveniles are similar to those of the adult, suggesting that osmotic regulatory mechanisms are precociously developed to allow the colonization of eutrophic inland waters

Eel (Anguilla anguilla L. 1758) population structure in the low course of the river Tiber (Latium, central Italy), and preliminary considerations on its contribution to escapement

European eel (Anguilla anguilla l., 1758) demographic structure was studied in the low course of the river Tiber (Latium, Italy), where a professional fishery targeted to eel has been operating for more than 30 years, with the aim to evaluate its present state in relation to a general decrease of the local stock. this reduction is revealed by the catch contraction following the reduced glass eel recruitment to this river, consistent with what is observed at the continental level. Monthly samplings were carried out from may to november 2006. A total of 454 specimen of Anguilla anguilla were examined in order to assess the developmental stage (on the basis of body colour: yellow eel, silver eel and intermediate), total length, weight and morphometric measures (pectoral fin length, vertical and horizontal eye diameter). A subsample of 229 specimen was sacrificed in order to collect otholits for age evaluation, gonads for sex determination, swimbladders for evaluation of nematode Anguillicola crassus infestation. the developmental classification has been tested by a supervised regression technique, the partial least squares analysis (pls). In order to estimate the Tiber eel population growth curve, age-at-length has been back-calculated by using a linear model regression of the total length on the caudal radius of the otholits. Theoretical growth has been calculated by von bertalanffy’s model. On the whole, eel population structure in the Tiber does not show great changes with respect to previous investigations, contrary to what expected in relation to a possible decrease in population density. The low recruitment level might still be sufficient to sustain eel density and population structure in the low course of the tiber, because fishing effort on juveniles has ceased in the meantime. Some preliminary considerations can be made in relation to the contribution of the tiber eel stock to overall escapemen

Otolith growth allometry measurements in the european EEL

Martech 2009 Third Marine Technology Workshop, november 19th - 20th 2009, Vilanova i la Geltrú, Barcelona.-- 2 pagesPeer reviewe

A COMPARATIVE STUDY OF EEL (ANGUILLA ANGUILLA (L.)) POPULATION STRUCTURE IN THREE SITES IN ITALY, AND PRELIMINARY CONSIDERATIONS ON THE RELATIVE CONTRIBUTION TO ESCAPEMENT.

Eel population structure has been evaluated in three sites, (river Tiber, Caprolace and Lesina lagoons) in Italy, within a project aimed at the setting up of a integrated approach to the eel conservation and management in the Mediterranean area. First results show both differences and similarities between the three sites: all populations consist mostly of yellow eels, but the Tiber population consists mostly of small sizes and young specimen, whereas Caprolace and L esina populations show a comparable size distribution class with a predominance of larger individuals, even if age structure in the two lagoons is different. Furthermore, the Tiber population shows a sex ratio with the undifferentiated fraction larger than the mature and the latter consists mostly of males, while in both lagoons a predominance of females has been observed. Evident differences have been observed in infection rate by Anguillicola crassus: very high in the Tiber and intermediate in Lesina, while no infestation has been detected in eels from Caprolace. These results allow to make some preliminary considerations on the different contribution of the riverine and lagoon environments to the escapement of silver eels, not only from a quantitative but also qualitative point of view

Habitat-use strategy of th European eel Anguilla anguilla in Italian waters as indicated by otolith SR/CA ratios

THE SR/CA RATIO IN FISH OTOLITHS CAN REFLECT THE SALINITY OF HABITATS, AND IS WIDELY USED TO RECONSTRUCT THE PAST MIGRATORY ENVIRONMENTAL HISTORY OF FISH. TO UNDERSTAND THE HABITAT USE AND MIGRATORY BEHAVIOR OF THE EUROPEAN EEL (ANGUILLA ANGUILLA) IN 3 DIFFERENT SALINITY HABITATS, TEVERE RIVER (TR, MONTHLY AVERAGE SALINITY = 0.0PSU), LESINA LAGOON (LL, 16.0±11.4 PSU), AND CAPROLACE LAGOON (CL, 38.1±4.5 PSU), SOUTHERN ITALY. THE SR/CA RATIOS IN OTOLITHS FROM PRIMORDIUM TO OTOLITH EDGE OF THE EEL WERE MEASURED BY ELECTRON PROBE MICRO-ANALYZER BASED ON THE 47 INDIVIDUALS RANDOMLY SELECTED FROM THE 180 EELS COLLECTED IN THE 3 HABITATS. THE RELATIONSHIP BETWEEN THE OTOLITH SR/CA RATIOS AND AMBIENT SALINITY WAS POSITIVELY CORRELATED (R2=0.63, P<0.01), WHICH FURTHER CONFIRMED THAT THE SR/CA RATIO IS A RELIABLE PROXY IN STUDYING THE MIGRATORY ENVIRONMENT HISTORY OF THE EEL. THE MEAN(RANGE) SR/CA RATIOS IN OTOLITH FROM ELVER STAGE UNTIL OTOLITH EDGE FOR THE EEL COLLECTED FROM TR, LL AND CL WERE 3.2±2.9 MMOL/MOL (0.3-6.1 MMOL/MOL), 7.8±4.2 MMOL/MOL (3.6-12MMOL/MOL) AND 10.1±3.9 MMOL/MOL (6.2-14MMOL/MOL), WHICH CORRESPONDED TO FRESHWATER, BRACKISH AND SEAWATER MIGRATORY CONTINGENTS, RESPECTIVELY. HOWEVER, THE PROPORTION OF INTER-HABITAT SHIFTERS WAS HIGHER IN THE POORLY PRODUCTIVE LAGOON AND LOWER IN THE RICHLY PRODUCTIVE BRACKISH LAGOON. THIS STUDY DEMONSTRATES THAT THE FACULTATIVELY CATADROMOUS MIGRATION OF EUROPEAN EEL WAS CONDITIONAL