Preliminary biological data on the northeast Mediterranean conger eel Conger conger L., 1758

Los ejemplares de congrio Conger conger L., 1758 provenientes de las campañas de primavera Medits (Mediterranean International Trawl Survey, primavera de 2002) y de otoño Grund (National Group for Demersal Resource Evaluation, otoño de 2001 y 2002) en el mar Adriático (Mediterráneo nororiental), entre 0 y 400 m de profundidad, tienen una longitud que oscila entre 21 y 130 cm y, con mayor frecuencia, entre 30 y 50 cm. La edad, determinada mediante la cuenta de los anillos y la medición del eje mayor de los estatolitos, se estima entre 3 y 8 años, con predominio de ejemplares de 4 y 5 años. El análisis histológico de las gónadas ha permitido identificar solo óvulos inmaduros. La dieta, más abundante en otoño, se constituye principalmente a base de Osteichthyes, Crustacea y Mollusca.Specimens of conger eel Conger conger L., 1758 from spring Medits (Mediterranean International Trawl Survey, spring 2002) and autumn Grund (National Group for Demersal Resource Evaluation, autumn 2001 and 2002) trawl surveys in the Adriatic (northeast Mediterranean) at depths of between 0 and 400 m, were found to measure in length from 21 to 130 cm, with greater frequency in the 30 to 50 cm range. Age determined on the basis of ring count and the length of the greater otolith axis was found to be between 3 and 8 years, with the majority of specimens in the 4- to 5-year range. Histological gonad analysis only revealed immature ovaries. The specimens were found to feed chiefly on Osteichthyes, Crustacea and Mollusca, which are most abundant in autumn.Instituto Español de Oceanografí

Environmental infuence on calcifcation of the bivalve Chamelea gallina along a latitudinal gradient in the Adriatic Sea

Environmental factors are encoded in shells of marine bivalves in the form of geochemical properties, shell microstructure and shell growth rate. Few studies have investigated how shell growth is affected by habitat conditions in natural populations of the commercial clam Chamelea gallina. Here, skeletal parameters (micro-density and apparent porosity) and growth parameters (bulk density, linear extension and net calcification rates) were investigated in relation to shell sizes and environmental parameters along a latitudinal gradient in the Adriatic Sea (400 km). Net calcification rates increased with increasing solar radiation, sea surface temperature and salinity and decreasing Chlorophyll concentration in immature and mature shells. In immature shells, which are generally more porous than mature shells, enhanced calcification was due to an increase in bulk density, while in mature shells was due to an increase in linear extension rates. The presence of the Po river in the Northern Adriatic Sea was likely the main driver of the fluctuations observed in environmental parameters, especially salinity and Chlorophyll concentration, and seemed to negatively affect the growth of C. gallina

Spawning of bluefin tuna in the black sea: historical evidence, environmental constraints and population plasticity

<div><p>The lucrative and highly migratory Atlantic bluefin tuna, <em>Thunnus thynnus</em> (Linnaeus 1758<em>;</em> Scombridae), used to be distributed widely throughout the north Atlantic Ocean, Mediterranean Sea and Black Sea. Its migrations have supported sustainable fisheries and impacted local cultures since antiquity, but its biogeographic range has contracted since the 1950s. Most recently, the species disappeared from the Black Sea in the late 1980s and has not yet recovered. Reasons for the Black Sea disappearance, and the species-wide range contraction, are unclear. However bluefin tuna formerly foraged and possibly spawned in the Black Sea. Loss of a locally-reproducing population would represent a decline in population richness, and an increase in species vulnerability to perturbations such as exploitation and environmental change. Here we identify the main genetic and phenotypic adaptations that the population must have (had) in order to reproduce successfully in the specific hydrographic (estuarine) conditions of the Black Sea. By comparing hydrographic conditions in spawning areas of the three species of bluefin tunas, and applying a mechanistic model of egg buoyancy and sinking rate, we show that reproduction in the Black Sea must have required specific adaptations of egg buoyancy, fertilisation and development for reproductive success. Such adaptations by local populations of marine fish species spawning in estuarine areas are common as is evident from a meta-analysis of egg buoyancy data from 16 species of fish. We conclude that these adaptations would have been necessary for successful local reproduction by bluefin tuna in the Black Sea, and that a locally-adapted reproducing population may have disappeared. Recovery of bluefin tuna in the Black Sea, either for spawning or foraging, will occur fastest if any remaining locally adapted individuals are allowed to survive, and by conservation and recovery of depleted Mediterranean populations which could through time re-establish local Black Sea spawning and foraging.</p> </div

Melatonin Induces Follicle Maturation in Danio rerio

Most organisms modulate their reproductive activity responding to day length by the nocturnal release of melatonin by the pineal gland. This hormone is also responsible for synchronizing reproduction with specific external environment stimuli in order to optimize reproductive success

Molecular Identification of Atlantic Bluefin Tuna (Thunnus thynnus, Scombridae) Larvae and Development of a DNA Character-Based Identification Key for Mediterranean Scombrids

The Atlantic bluefin tuna, Thunnus thynnus, is a commercially important species that has been severely over-exploited in the recent past. Although the eastern Atlantic and Mediterranean stock is now showing signs of recovery, its current status remains very uncertain and as a consequence their recovery is dependent upon severe management informed by rigorous scientific research. Monitoring of early life history stages can inform decision makers about the health of the species based upon recruitment and survival rates. Misidentification of fish larvae and eggs can lead to inaccurate estimates of stock biomass and productivity which can trigger demands for increased quotas and unsound management conclusions. Herein we used a molecular approach employing mitochondrial and nuclear genes (CO1 and ITS1, respectively) to identify larvae (n = 188) collected from three spawning areas in the Mediterranean Sea by different institutions working with a regional fisheries management organization. Several techniques were used to analyze the genetic sequences (sequence alignments using search algorithms, neighbour joining trees, and a genetic character-based identification key) and an extensive comparison of the results is presented. During this process various inaccuracies in related publications and online databases were uncovered. Our results reveal important differences in the accuracy of the taxonomic identifications carried out by different ichthyoplanktologists following morphology- based methods. While less than half of larvae provided were bluefin tuna, other dominant taxa were bullet tuna (Auxis rochei), albacore (Thunnus alalunga) and little tunny (Euthynnus alletteratus). We advocate an expansion of expertise for a new generation of morphology-based taxonomists, increased dialogue between morphology-based and molecular taxonomists and increased scrutiny of public sequence databases.Versión del editor4,411

Volunteers in marine conservation monitoring: a study on the distribution of seahorses carried out in collaboration with recreational scuba divers.

Seahorses (Hippocampus) live in tropical and temperate waters. Habitat degradation and fishery overexploitation have led to drastic population declines on a global scale. Population monitoring is therefore essential to determine current status and manage conservation. In this first study in Italian waters on the geographical and ecological distribution of the two Mediterranean species, Hippocampus hippocampus and Hippocampus ramulosus, recreational scuba divers were recruited and trained to report sightings. A specially formulated questionnaire was produced and distributed to scuba diving schools and centres. In the 3-year study, 2536 divers spent 6077 diving hours gathering data and completed 8827 questionnaires. Eight percent of the questionnaires showed seahorse sightings, for a total of 3061 sighted specimens, 68% of which referred to Hippocampus ramulosus. The two species had overlapping geographic distributions. Seahorse abundance varied with the northern Adriatic Sea showing greatest abundance followed by the central-southern Tyrrhenian Sea; seahorses were rare in the Ligurian and northern Tyrrhenian Seas. Preferred habitats were shallow areas with either sandy bottoms or Posidonia oceanica (L.) Delile meadows. Seahorse distribution may be correlated with the degree of degradation of P. oceanica meadows. Resource users, like divers, were shown to be willing to take part in biological monitoring and can contribute both in scientific terms by collecting considerable amounts of data over short time periods, and in economic terms by decreasing costs. The greatest limitation with volunteers was the difficulty in obtaining a uniformly distributed sample across time and space. We conclude that recreational divers can play an active part in monitoring the marine environment and that the Mediterranean Hippocampus Mission may be used as a model for biodiversity monitoring