Data on discards were collected during deep-water bottom seasonal trawling surveys targetting red shrimps (Aristeus antennatus and Aristaeomorpha foliacea) in the Ionian Sea (Eastern-Central Mediterranean). The performance of 3 codends, with stretched mesh sizes of 40, 50 and 60 mm, was tested. A cover with a stretched mesh of 20 mm was employed on each codend.The discarded catch constituted an important fraction of the total catch (2050%). This was almost exclusively due to unwanted fish species, while discards of the target species and other commercial species were negligible. Discard rates increased with total catch and depth.No substantial differences were seen in the overall performance of the codends used. Differences were only detected in the biomass of the escaped fraction of the catch (both marketable and discards) and in the size selectivity. The 40 mm mesh size was not selective in Aristeus antennatus. Larger mesh size codend (50 and 60 mm) allowed a higher number of small specimens to escape. The 50% retention sizes increased according to the mesh size in all examined species.
The search for new fishing grounds in Greek waters, has led to the investigation of unexploited resources on the continental slope of the Northeastern Ionian Sea (Central Mediterranean Sea). Four seasonal experimental surveys were carried out by Greek and Italian commercial trawlers from September 1999 to September 2000, in the framework of the project called "Interregional environmental studies in the Ionian Sea". Potential targets included deep-water species of fishes, crustaceans and cephalopods.During the 4 surveys, a total of 25 species of cephalopods belonging to 10 families were recorded, including 10 oegopsid squids, two myopsid squids, five octopods, two cuttlefishes and six sepiolids. Sepietta oweniana was the most abundant species, followed by Todaropsis eblanae, Illex coindetii and Loligo forbesi. Some uncommon species such as Ancistroteuthis lichtensteini, Ctenopteryx sicula and Galiteuthis armata, were recorded for the first time in the study area. An extension of the depth range was recorded for several species.The results of multivariate analyses, based on Bray-Curtis similarity indices, showed the presence of two associations: one consisting of hauls carried out at depths of 250500 m, where Sepietta oweniana, Todaropsis eblanae and Loligo forbesi were most frequently caught, and another comprising deeper hauls (up to 800 m depth) characterized by typical species of the slope, such as, Pteroctopus tetracirrhus, Neorossia caroli, Todarodes sagittatus and Abralia veranyi.The number of cephalopod species and the hourly yield decreased with depth and varied with season. The highest mean cephalopod catches per hour (>6kg/hr) were observed in the depth zone 250500 m in September 1999 and 2000, resulting in a higher percentage (5%) of cephalopods in the total catch. Of the cephalopod species collected, Loligo forbesi, and of the ommastrephid squids, Todaropsis eblanae, Todarodes sagittatus and Illex coindetii, were of commercial interest.
The population biology and life strategies of Chlorophthalmus agassizii were studied in the Ionian Sea (eastern–central Mediterranean) using the data collected during the experimental trawl surveys carried out from 1995 to 2000. Depth-related trends of both density and size were found. With depth the former decreased while the latter increased. A typical bigger–deeper phenomenon was detected: young-of-the-year individuals occur on the shelf during autumn–winter months and move towards bathyal bottoms as they grow. The sampled population was made up of several size–age groups. The maximum age of 8 years was identified by means of otolith readings. The Von Bertalanffy growth parameters were estimated from the age–length key (Linf=189.04±5.401 mm; k=0.24±0.021; to= 1.20± 0.132; /¢=3.94) and modal progression analysis (Linf=218.33±18.397 mm; k=0.164±0.028; to= 1.694±0.171; /¢=3.89). Reproduction of this monoecious fish was observed during summer–early autumn. Considering the female portion of the gonad, the size at attainment of 50% maturity was 115 mm TL. The corresponding age is within the third year of life. The simultaneous occurrence of oocytes in different development stages was shown in the ovary. Both the asynchronous ovary and oocyte size distribution indicate that C. agassizii spawns more than once during a reproductive season (batch spawner). Functional fecundity (on average 3,018 hydrated oocytes) was between 37 and 69% of the absolute fecundity and increased significantly with the individual size. Since adult specimens are mostly distributed on the slope, eggs and larvae develop in epipelagic waters and migrate in-shore where juvenile forms recruit on the shelf. Juveniles migrate ontogenetically towards deeper bottoms and after 2–3 years start to reproduce annually within a life span greater than 10 years
SUMMARY: Data on the distribution, abundance and biological parameters of the giant red shrimp Aristaeomorpha foliacea were collected during a research survey in deep waters (600-4000 m) of the Mediterranean Sea at three locations: the Balearic Sea, the western Ionian and the eastern Ionian in early summer 2001. The shrimp was mainly found in the shallower zone (< 1000 m) of the eastern Ionian Sea. Few specimens were caught in the deeper waters of this region, with 1100 m being the lower limit of its distribution. This is the maximum depth reported for the species in the Mediterranean. At the other two locations, the species was scarcely caught and only in the shallowest zone (< 1000 m). In the area and depth zone of high abundance, 5 modal groups for females and 3 for males were distinguished using the Bhattacharya method. The recruitment seems to take place at the shallowest stations (600 m). More than 50% of adult females were in advanced maturity stages. The striking abundance differences of the species between the western and eastern locations may be explained by the different exploitation level of the deep waters (almost null in the eastern Ionian Sea and extensive more westwards). However, the distribution and biological characteristics of A. foliacea indicate a higher vulnerability to over-fishing comparing to the other commercial co-occurring deep-water shrimp Aristeus antennatus.Key words: Aristaeomorpha foliacea, distribution, biology, deep waters, Mediterranean. RESUMEN: BIOLOGÍA DEL MEDITERRÁNEO PROFUNDO: EL CASO DE ARISTAEOMORPHA FOLIACEA (RISSO, 1827) (CRUSTACEA: DECAPODA: ARISTEIDAE). -Se obtuvieron datos sobre distribución, abundancia y parámetros biológicos de la gamba gigante Aristaeomorpha foliacea durante una campaña de investigación en aguas profundas (600-4000 m) en tres localidades a lo largo del Mediterráneo: región Balear, Iónico occidental y Iónico oriental, que tuvo lugar en verano de 2004. Esta gamba fue encontrada mayoritariamente en la zona menos profunda (< 1000m) del Iónico oriental. En aguas más profundas de esta región (1100 m) se encontraron menos ejemplares, pero determinó el límite inferior de su distribución. Esta es la máxima profundidad registrada en el Mediterráneo para esta especie. En las otras dos localidades, esta especie fue escasa y solo se encontró en la zona menos profunda (< 1000 m). En el área y en la profundidad de máxima abundancia, se observaron 5 grupos modales de hembras y 3 de machos mediante el método de Battacharya. El reclutamiento parece que tiene lugar en aguas menos profundas (600 m). Más del 50% de las hembras adultas se encontraron en avanzado estado de madurez gonadal. Esta curiosa diferencia entre la parte más occidental y las localidades más orientales puede explicarse por el diferente nivel de explotación en las aguas profundas (casi nulo en el Iónico oriental e intensivo más al oeste). Sin embargo, la distribución y características biológicas de A. foliacea indican una vulnerabilidad alta a la sobre-explotación pesquera si la comparamos con o...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.