Fishery resources: between ecology and economy

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Spatio-temporal changes of Munida Rutllanti Zariquiey-Alvarez, 1952 (Decapoda: Galatheidae) in the North-Western Ionian Sea (Central Mediterranean)

The spatio-temporal pattern of Munida rutllanti distribution in the north-western Ionian Sea has been studied. Data were collected during 14 experimental trawl surveys conducted from 1997 to 2010 as part of the international MEDITS project. The hauls were carried out during day-light hours between depths of 10 and 800 m in the spring season. A progressive increase in the abundance index (N/km2) of M. rutllanti was observed from 2000 to 2008, then a sharp decrease was shown in the last two years. The greatest and lowest abundance indices were observed in the Apulian and central Calabrian sub-areas, respectively. The species was collected between 107 and 795 m in depth, with a significant increase and decrease over time in the maximum and minimum depth of finding, respectively. A highly significant increase over time in the mean carapace length was also observed in the whole study area. The widespread occurrence and increasing abundance of this species in the Ionian Sea could be related to the increase in temperature and the variation in hydrographic conditions which occurred in the Ionian basin during the EMT-BiOS phenomenon

Testicular activity and sperm glycoproteins in giant red shrimp Aristaeomorpha foliacea

The reproduction of male giani red shrimp Aristaeomorpha foliacea, collected from thè late winterto thè summer in thè north-western lonian Sea (Mediterranean Sea), was investigated using histological and histochemistry methods. Seasonal changes in thè spermiogenesis and thè glycoprotein pattern were found and sperm glycoproteins matured as gametes moved from thè testis to thè terminal ampliila. In serial sections stained with hematoxylin and eosin thè testicular activity appeared to be discontinuous. In late winter thè testes had no meiotic activity and thè seminiferous epithelium consisted of interkinetic spermatogonia and spermatozoa. In spring, spermiogenetic activity was high and thè seminiferous epithelium mainly consisted of spermatocytes and spermatozoa while in summer, thè testes were again inactive since both spermatocytes and spermatozoa were lacking. The use of twelve different lectins indicated that thè intratesticular spermatozoa from late winter to summer contain surface binding sites for SNA, MAA, Con A and KOH-sialidase (si)-WGA. In March and July they also exhibited nuclear and cytoplasmic reactivity for SNA and Con A. In thè hemispermatophore thè spermatozoa displayed a more complex lectin-binding pattern because they also reacted with PNA, DBA, HPA, OSA II. The staining with DBA, KOH-si- DBA, and OSA II showed differences between thè spermatozoa from late winter-spring hemispermatophores and summer hemispermatophores: thè former showed a nuclear affinity whereas thè latter displayed surface and/or cytoplasm staining. No reaction was observed with SBA, GSAI-B4, UEA I, and LTA

A trophic model of the benthopelagic fauna distributed in the Santa Maria di Leuca cold-water coral province (Mediterranean Sea)

The benthopelagic fauna distributed in and around the Santa Maria di Leuca (SML) cold-water coral (CWC) province (Northern Ionian Sea–Central Mediterranean Sea) was analyzed through the development of a mass-balanced ecosystem model. A total of nine balanced simulations were provided taking into account the biomass data collected during several experimental bottom trawl surveys carried out from 2005 to 2010 in a depth range between 101 and 541 m. A total of 100 species were included in the analysis corresponding to 15 cephalopods, 25 crustaceans, 7 chondrichthyes and 54 osteichthyes. Simulations were developed maintaining the species-level detail. The total system throughput estimated in the SML CWC province trophic web resulted mainly due to consumption and about 80% of it was maintained by species with trophic level between 2 and 4. Results highlighted important features in terms of the structure and functioning of the system, such as the high level of activity maintained by intermediate trophic levels and the important role of top-down control in the faunal assemblage due to both vertebrate and invertebrate species

Assessment of cetacean–fishery interactions in the marine food web of the Gulf of Taranto (Northern Ionian Sea, Central Mediterranean Sea)

AbstractThe exploitation of fishery resources acts as a driving force on cetaceans both directly, by determining their fishing mortality or injury as by-catch species, and indirectly, through the lowering the availability of their prey. This competitive overlap between fishing and cetaceans often results in inadequate solutions so that in some cases there have been cases of intentional cetacean culling to maximize fishing production. A modelling approach applied to investigate the ecological roles of cetaceans in the food web could prove more effective to integrate ecological and fishing aspects and to provide suggestions for management. The comparative analysis carried out in the Gulf of Taranto (Northern Ionian Sea, Central Mediterranean Sea) showed that fishing exploitation provides impacts on the investigated food web greater than those due to cetacean predation. Trawling was estimated to be the most negatively impacting fishing gear considering the mortality rates and consumption flows. On the other hand, the striped dolphin was the main impact on the food web due to its highest consumption flows. Analysis showed a negative and non-selective impact on the exploited species due to the fishing gears, while the odontocetes proved to select their prey species and provide a positive impact in the assemblage. In particular, while the fishing gears are primarily size selective, targeting mostly large and economically valuable fish, the odontocetes seem to follow a co-evolution process with their prey, developing a specialization in their resources, providing control of the meso-consumers and ensuring a trophic stability in the ecosystem

Does the Bari Canyon (Central Mediterranean) influence the fish distribution and abundance

Abstract The objective of this study was to evaluate whether the Bari Canyon influences the distribution and abundance of fish fauna in the southern Adriatic Sea. Data were collected in the Bari Canyon and in an adjacent area on the continental slope during an experimental longline survey carried out in June 2015. A total of 19 fish species were collected (16 inside and 13 outside the canyon). Differences between the sites were evaluated by means of a set of univariate and multivariate methods (analysis of variance, permutational multivariate analysis of variance, non-metric multidimensional scaling). The abundance and biomass of the whole catch were significantly greater inside than outside the canyon. The most abundant species were the shark Galeus melastomus and the teleost fishes Conger conger, Helicolenus dactylopterus, Merluccius merluccius, Pagellus bogaraveo and Phycis blennoides. All these species were found to be more abundant in the canyon than in the adjacent area. However, a significantly greater abundance inside the canyon than outside was detected for C. conger, while P. blennoides showed both significantly greater abundance and biomass in the canyon than outside. P. bogaraveo was exclusively caught inside the canyon. C. conger and P. blennoides exhibited significant differences in their sizes between the canyon and the adjacent area: a greater number of both smaller and larger individuals were found in the canyon than on the open slope. Mature females and males were mostly observed in the canyon in all the most abundant species, with the exception of P. blennoides due to its autumn-winter spawning. The present study corroborates the role of the Bari Canyon as a refuge area and an Essential Fish Habitat for fish species exploited in the neighbouring fishing grounds, highlighting the need for conservation measures