Minutus Capelanus Research Articles

Can a square-mesh panel inserted in front of the codend improve the exploitation pattern in Mediterranean bottom trawl fisheries?

A 50mm square-mesh panel was inserted in front of the codend in a Mediterranean bottom trawl as an attempt to improve the exploitation pattern for Trachurus trachurus (Atlantic horse mackerel), Merluccius merluccius (European hake), Mullus barbatus (red mullet), Trisopterus minutus capelanus (poor cod), Illex coindetii (broadtail shortfin squid), and Parapenaeus longirostris (deep-water rose shrimp). Escapement through the square-mesh panel was low, never estimated to be above 10% of the total escapement, implying that a square-mesh panel inserted in front of the codend only had minor effect on the exploitation pattern in the fishery.

Relationship of otolith length to fish total length in six demersal species from the NW Mediterranean Sea

Summary Relationships between otolith major axis length (mm) and fish size (total length, cm) were described by means of linear regression analysis for six demersal fish species from the NW Mediterranean: blue whiting (Micromesistius poutassou), greater forkbeard (Phycis blennoides), red mullet (Mullus barbatus), poor cod (Trisopetus minutus capelanus), horse mackerel (Trachurus trachurus), and Mediterranean mackerel (Trachurus mediterraneus). Results show that reconstruction of body size from otolith measurement is possible by applying this approach based on the relationship of otolith length – fish length.

The effect of mesh configuration and codend circumference on selectivity in the Mediterranean trawl Nephrops fishery

The Pomo pit area is both the main Adriatic nursery area for European hake ( Merluccius merluccius) and Norway lobster ( Nephrops norvegicus) and an important trawling ground for the Adriatic trawl fleet. The current paper is not only restricted to the escapement of Norway lobster but also takes note of the associated white fish community (European hake, blue whiting Micromesistius poutassou and poor-cod Trisopterus minutus capelanus) which makes an important contribution to the commercial catch of trawlers. This study was undertaken to analyse the effect on trawl selectivity of inserting first a 40 mm square-mesh codend and second of increasing the circumference in the diamond-mesh codend. A traditional 40 mm diamond-mesh codend, typical of the commercial trawl fisheries, was selected as a reference codend for the comparative analysis. The square-mesh codend was always more selective than the diamond-mesh codends, while the influence of codend circumference on diamond-mesh selectivity was less evident. In addition to mesh configuration and the number of meshes around the codend, the selectivity data were modelled by estimating the individual contribution of catch size and season, but there was no evidence of a coherent effect on the selectivity of these two parameters. This study confirms that all the four investigated species make the best use of the square-mesh opening, either because of their body shape or because the form of the mesh facilitates forcing of the net. Results seem to suggest that for the main target species, Norway lobster, square-mesh codend would protect specimens under the 20 mm of MLS (carapace length). Square-mesh also improves the L50 of European hake, but it seems not to be sufficient to avoid the catch of specimens under MLS of 20 cm as fixed by the EC Reg. Nr. 1967/2006. In conclusion, enforcement of installation of square-mesh codends in Mediterranean trawl Nephrops fishing could contribute to decreasing the capture of individuals from the particular nursery area of Pomo pit.

Size selection by diamond- and square-mesh codends in multi-species Mediterranean demersal trawl fisheries

Mediterranean demersal trawl fisheries traditionally operate using small diamond-shape meshes in the codend, which tend to retain almost all animals. We investigated the effect of mesh configuration on the size selectivity of nine species (the scaldfish Arnoglossus laterna, the broad-tail shortfin squid Illex coindettii, the European hake Merluccius merluccius, the red mullet Mullus barbatus, the Norway lobster Nephrops norvegicus, the common pandora Pagellus erythrinus, the deepwater rose shrimp Parapenaeus longirostris, the Mediterranean horse mackerel Trachurus mediterraneus and the poor-cod Trisopterus minutus capelanus) commonly captured in the Mediterranean demersal trawls. Two codends having meshes with the same opening (ca. 38 mm) but different mesh configuration (DM38: diamond-mesh and SM38: square-mesh configuration) were fished daily and alternately on the same trawl. They demonstrated a substantial improvement in selectivity with square-mesh. Selectivity was measured using the covered codend technique, the cover being supported by circular hoops. The results were analysed taking into account the between-haul variation in selectivity. Two other important external variables were identified: the trawling depth and the codend catch, which for some species influenced between-haul variation, but there was no evidence of a coherent effect on selectivity parameters. The selectivity of 40 mm diamond-mesh codend has been reported to be rather poor because a large proportion of the codend catch is immature and smaller than the minimum landing size (MLS) or first maturity size. With the exception of the flatfish ( A. laterna), the effect of a change of mesh configuration from diamond- to square-mesh on size selectivity positively affected the retention length at 50% ( L 50). However, square-meshes were found to be unsuitable for flat and/or deep-bodied fish as these escape more readily from diamond-meshes. The Council Regulation (EC) No. 1967/2006, concerning management measures for the sustainable exploitation of fishery resources in the Mediterranean, establishes the MLS of marine organisms. However, the increase in L 50 with square-mesh would not avoid some of the existing contradictions in allowing the use of codend mesh which leads to lower L 50 than the MLS.

Identification of gadoid species (Pisces, Gadidae) by sequencing and PCR–RFLP analysis of mitochondrial 12S and 16S rRNA gene fragments

We applied PCR–RFLP (Polymerase Chain Reaction – Restriction Fragment Length Polymorphism) analysis to identify seven gadoid species of different biogeographical origin and commercial relevance, namely Gadus morhua (Atlantic ocean); Trisopterus minutus capelanus, Trisopterus minutus minutus, Molva elongata, Phycis blennoides, Micromesistius poutassou (Atlantic ocean and Mediterranean sea); Theragra chalcogramma (Pacific ocean). Two DNA fragments belonging to mitochondrial 12S and 16S rRNA genes of about 430 and 630 bp, respectively, were isolated by PCR amplification. Their direct sequencing showed a significant genotypic diversity among gadoid species, useful for species identification. Digestion of 16S rRNA gene PCR fragment with MvaI or Bsh1285I restriction enzymes, followed by agarose gel electrophoresis of the cleaved products, yielded specific restriction profiles that enabled direct, visual identification of the species analyzed. This PCR–RFLP method allowed a clear and rapid discrimination of the gadoid species studied.

Day–night variations in the demersal nekton assemblage on the Mediterranean shelf-break

The composition of the demersal nekton assemblage inhabiting the Mediterranean shelf-break of west-central Italy was examined to investigate the diel variation in species composition and abundance. Fish were obtained during four 24-h sampling periods that represented the four annual seasons. Thirty-two hauls (eight in each season) were conducted in a shelf-break area at 140–160 m depth. The density of fish, crustaceans, and decapods exhibited differences on short- and long-term time scales: multidimensional scaling suggested that season and light intensity may be important factors influencing fish assemblage composition. At the diel scale two main assemblages separating nocturnal and diurnal hauls were identified. The typical assemblage structure of shelf-break bottoms was represented during daylight by species such as Merluccius merluccius, Capros aper, Serranus hepatus, Macroramphosus scolopax and Trisopterus minutus capelanus. At night, the assemblage showed a drastic change due to the increase of small nektobenthic species, Argentina sphyraena and Glossanodon leioglossus, together with cave-dwelling fish ( Gnathophis mystax, Chlopsis bicolor, Nettastoma melanurum) and nektobenthic crustaceans (i.e., Parapenaeus longirostris and Solenocera membranacea). The above-mentioned differences in species composition may be related to changes in vertical distribution for trophic needs ( M. merluccius) and/or in the shoal structure ( A. sphyraena and G. leioglossus). The lack of data on the pattern of trawl catchability of Mediterranean species during the day may lead to an inaccurate estimation of species abundance when only diurnal trawl survey data are used.

Body shape and trawl cod end selectivity for nine commercial fish species

This study investigates the catch components of a commercially used demersal trawl cod end in Izmir Bay, and reveals some of the morphological characteristics of nine commercial fish species; red mullet (Mullus barbatus), hake (Merluccius merluccius), whiting (Merlangius merlangus euxinus), poor cod (Trisopterus minutus capelanus), tub gurnard (Trigla lucerna), common pandora (Pagellus erythrinus), axillary sea bream (Pagellus acarne), picarel (Spicara smaris) and annular sea bream (Diplodus annularis) in relation to mesh size and shapes. Furthermore selectivity of 40-mm polyethylene netting cod end for red mullet, hake, common pandora, axillary sea bream, picarel and annular sea bream is presented. The results are discussed in a way to understand the probable effects of fish body shape on mesh selectivity.

Eastern and Western Poor Cod (Trisopterus minutus capelanus) Populations in the Mediterranean Sea: Evidence from Allozyme and Minisatellite Loci

Abstract. Nine allozyme and two minisatellite loci were used to investigate potential genetic differentiation among three samples of Mediterranean poor cod, Trisopterus minutus capelanus, from the Gulf of Lion, the Tuscan Archipelago and the Aegean Sea. Both types of markers showed consistent results, with FST values of 0.0262 and 0.0296 (P < 0.0015, after Bonferroni correction for multiple tests) for allozymes and minisatellites, respectively. Allele frequency heterogeneity tests between pairs of samples showed a clear separation between the two western Mediterranean samples (Gulf of Lion, Tuscan Archipelago) and the eastern one (Aegean Sea). The results indicate that at least two reproductively isolated populations of poor cod occur in the Mediterranean.

Recruitment dynamics of eight fishery species in the northwest Mediterranean Sea

The recruitment dynamics into the fishery of eight species in the northwestern Mediterranean Sea was studied on the basis of a monthly length sampling on commercial landings lasting one year (March 1999-February 2000). The results show that three species or groups of species ( Mullus barbatus and M. surmuletus, Eledone cirrhosa and Loligo vulgaris ) recruited mostly during a well-defined and regular season, while recruitment of the rest of species ( Merluccius merluccius, Micromesistius poutassou, Phycis blennoides, Sepia officinalis and Trisopterus minutus capelanus ) took place all year round, though with seasonal peaks. Landings of small Merluccius merluccius showed a progressive declining trend from the early 1990s, while the opposite was found for Mullus barbatus and M. surmuletus

Feeding Habits of Trisopterus minutus capelanus (Gadidae) Off the Eastern Coast of Spain (Western Mediterranean)

Abstract. The stomach contents of poor cod, Trisopterus minutus capelanus (Lacepède), were taken at monthly intervals off the eastern coast of the Gulf of Valencia (Spain). A total of 1276 were analyzed to determine diet according to fish size and season. The basic food consists of crustaceans (Mysidacea and Decapoda) and teleosts. Feeding habits varied with size: decapods and fishes were more abundant in the stomachs of larger specimens. Little seasonal variation in food habits was recorded.

Allozyme analyses of the genus Trisopterus: taxonomic status and population structure of the poor cod

Genetic analysis of the four Trisopterus (Gadidae) taxa suggests that the interrelationships of the two morphs of poor cod (T. minutus minutus in the Atlantic and T. minutus capelanus in the Mediterranean) should be reconsidered. The Mediterranean poor cod T. m. capelanus is more closely related to bib T. luscus than to the Atlantic poor cod, so the population structure in the Atlantic and Mediterranean poor cod must be considered separately. Among 635 Atlantic individuals there was some evidence of poor cod population differentiation (allele frequency heterogeneity test P <0·0005; FST=0·0135, P≤0·0005). Levels of genetic variation were similar to those reported for related gadoid species. Some differentiation was present on the Norwegian coast (samples from Trondheimsfjord) and between the Faeroe Islands (Faeroe Bank) and the adjacent European coastal location. In contrast no statistically significant population differentiation was evident in Mediterranean poor cod, but fewer samples and individuals were screened.

Escapement from the main body of the bottom trawl used for the Mediterranean international trawl survey (MEDITS)

Escapement through the body or under the footrope of the sampling trawl used for the Mediterranean international trawl survey programme (MEDITS) was assessed i) by means of visual observations performed with a towed operating vehicle equipped with a high-sensitivity video camera, and ii) by attaching small bags to the outside of the trawl body and under the footrope. Due to the small size of most of the individuals present in the study area and to the towing speed, fish behaviour in front of the trawl could not be frequently observed. In contrast, their behaviour was easily observed inside the net, especially upstream and inside the codend. Some species, such as horse mackerel ( Trachurus sp.), showed greater swimming endurance compared with others such as annular seabream ( Diplodus annularis). In three fishing trips conducted in different seasons in 1996 and 1997 to obtain data on several species in different areas of the Adriatic, six small net bags were mounted outside the body of the MEDITS trawl to quantify escapement through the trawl belly and under the footrope. Significant escapement of many species occurred in the near-bottom part of the side panels. Norway lobster ( Nephrops norvegicus) had the highest rate (64 %), mainly represented by small-size individuals. The escapement of greater forkbeard ( Phycis blennoides) was also high (53 %). For hake ( Merluccius merluccius), common pandora ( Pagellus erythrinus) and poor cod ( Trisopterus minutus capelanus), rates ranged from 10 to 16 %. The escapement of red mullet ( Mullus barbatus) was very low despite their great abundance. Blue whiting ( Micromesistius poutassou) escaped mainly through the mid-height part of the side panel. This great variability of escapement values could affect the proportion rates of the species sampled during a standard survey. Different escape behaviours among size classes were observed for M. poutassou, T. minutus capelanus and P. erythrinus, with smaller individuals tending to escape towards the bottom and larger ones towards the higher parts of the trawl body. In the species where the escape rate was size-dependent, therefore, the size-frequency distributions obtained from the codend catch may not reflect actual size-frequency distributions.

Size selectivity of diamond and square mesh codends for four commercial Mediterranean fish species

In the present study, we compared the size selectivity of the 14 mm (knot-to-knot) diamond-shaped codend (14D), presently used in Hellenic waters, with those of 20 mm square-shaped (20S) and 20 mm diamond-shaped (20D) codends for four commercially important demersal species (Merluccius merluccius, Micromesistius poutassou, Trisopterus minutus capelanus and Lepidorhombus boscii). Codend selectivity was estimated using the covered codend method. Our results suggested that 14D was not selective for any of the target species and the proportion retained by 14D ranged between 0.88 and 1. In addition, only in the case of M. merluccius did the results suggest that 20S is significantly more selective and retains fewer under-sized fish than 20D. With the exception of M. merluccius, the direct estimation of the 14D L50 values was not possible, because of the small number of specimens retained by the cover codend of 14D. The L50 value of M. merluccius for 14D was lower than its currently enforced minimum landing size (MLS) and length at 50% maturity. In contrast, for 20S and/or 20D codends, even though the estimated L50values were generally close to, or higher than, the species’ MLS, the L50 value of 20S for M. merluccius and that of 20D for L. boscii, were much smaller than their lengths at 50% maturity, a fact indicating that even the use of 20S and 20D, respectively, provides small opportunities for reproduction. Hence, the appropriate mesh sizes for these two species must be greater than 20 mm and their MLS must be raised. In contrast, forT. m. capelanusand M. poutassou, the L50values of 20D (but not of 14D) were close to their lengths at 50% maturity, a fact indicating that 20D is appropriate for these two species. The above mentioned facts clearly showed that: (a) 14D is harmful, in terms of size of landed fish, for the Hellenic demersal stocks and hence its use should be discontinued and (b) the use of a single appropriate mesh size for the Mediterranean trawl fishery as a whole is impossible because of its multispecies nature and the diVerent body sizes of species involved. Since the majority of the individuals escaping through the meshes of 20D or 20S are immature and under-sized (i.e. their length is smaller than MLS), the replacement of 14D by either 20D or 20S, the former being the codend mesh size proposed by EU for the entire Mediterranean, will be accompanied by increased yield per recruit. ? 1997 International Council for the Exploration of the Sea

Feeding ecology of Mediterranean poor cod, Trisopterus minutus capelanus (Lacepede), from the eastern coast of Greece

The stomach contents of Mediterranean poor cod ( Trisopterus minutus capelanus) collected off the eastern coast of Greece (Euboikos Gulf) were analyzed. Crustaceans constituted the main food. Shrimps, followed by crabs, were the most important crustacean prey, in terms of frequency of occurrence. Mysids, although dominant in numbers, represented only a small percentage of the diet by weight. Euphausids, Macrura Reptantia and anomurans were the other main crustaceans found in the stomachs, whereas amphipods, copepods, isopods and cumaceans were present in negligible quantities. Fish ranked second in importance and most were epibenthic or demersal species. Variations in the food of poor cod related to its length were mostly qualitative and not quantitative in terms of stomach fullness. Smaller poor cod fed mainly on mysids and crangonids, but, as fish size increased, these food organisms were replaced by large shrimps (mainly alpheids), fish and crabs. Finally, there was evidence for seasonal and regional variation of the quantity and quality of the food consumed.

Parasites as biological markers: evolutionary relationships in the heterospecific combination of helminths (monogeneans) and teleosts (Gadidae)

Analysis of the genetic structure (11 loci) of helminth populations (Monogenea, Diclidophora), parasites of two teleost species (Gadidae, Trisopterus luscus and T. minutus minulus) which are sympatric in the Atlantic, revealed the existence of two species which were specific to each of the two hosts. A strong genetic similitude was found between one of these species (Diclidophora luscae), a parasite of T. luscus and a monogenean population parasitizing a third Gadidae (Trisopterus minutus capelanus) in the Mediterranean. These results led to a re-examinination of the evolutionary systematics of the three host taxa of the genus Trisopterus. Genetic analysis showed differences between the two subspecies T. minutus minutus (Atlantic) and T. minutus capelanus (Mediterranean) at eight of the 16 loci studied. However, there was no significant genetic divergence between T. luscus and T.m. capelanus. A new phyletic structure in the genus Trisopterus is proposed and the evolutionary trends within the Gadidae/Monogenea system are discussed.

Recruitment, length at first maturity and feeding of poor‐cod,Trisopterus minutus capelanus, in the northern Tyrrhenian Sea

Abstract Although Trisopterus minutus capelanus is not a valuable resource in the northern Tyrrhenian Sea, it is an important ≪by‐catch≫ for otter trawlers in abundance, biomass and frequency of occurrence. Most likely, this species plays a major role in the demersal system economy. As a contribution to a greater knowledge and understanding of the biology and ecology of this fish, the results of three years trawl surveys are presented.

Mercury assessment and its relation to selenium levels in edible species of the northern Tyrrhenian sea

Several species of marine organisms from the northern Tyrrhenian sea used as food were analysed for mercury and selenium. The species chosen were those considered most important both commercially and for their abundance in the area, Merluccius merluccius, Eledone cirrhosa, Trisopterus minutus capelanus and Nephrops norvegicus. The flatfish Solea vulgaris and Lepidorhombus boscii were considered as well. In all the species except E. cirrhosa Hg concentration increased with length. Furthermore the metal content was high in all the species except in sole. No significant HgSe correlation was found in any of the studied species.