Axillary Seabream Research Articles

Food partitioning and diet temporal variation in two coexisting sparids, Pagellus erythrinus and Pagellus acarne

Resource partitioning in two congeneric sparids, pandora Pagellus erythrinus and axillary seabream Pagellus acarne, was investigated using stomach content analysis integrated with data on stable isotopes (δ(15) N and δ(13) C). The study was carried out on coastal muddy bottoms in the Gulf of Castellammare (southern Tyrrhenian Sea, western Mediterranean Sea) in seasons (autumn, November 2004; winter, March 2005; spring, early June 2005), at depths between 50 and 100 m. Stomach content analysis suggested low trophic niche overlap between the two species. Pagellus erythrinus mainly preyed on strictly benthic organisms (polychaetes, brachyuran crabs and benthic crustaceans). Although it consumed benthic prey, P. acarne preferred suprabenthic prey such as peracarid crustaceans from the benthic boundary layer a few metres above the bottom. The two species showed different isotopic values, with P. erythrinus exhibiting higher δ(15) N and more enriched δ(13) C than P. acarne, in accordance with its marked benthic behaviour and high predation on carnivore polychaetes. Significant temporal variability in both diet and isotopic values caused trophic differences between the two species. The autumn and winter diet differed from the spring diet and the trophic levels of both species increased from autumn and winter to spring, in accordance with variations in food availability and changes in prey δ(15) N and δ(13) C. These temporal variations may be linked to an increase in energy requirements for reproduction, together with the differing availability of preferred prey throughout the year. Significantly, lower δ(13) C was recorded in fishes collected in winter (March), suggesting the influence of river inputs as a source of particulate organic matter in this zone after the flooding season. In conclusion, these sympatric congeneric fish species displayed clear food partitioning throughout the temporal scale analysed.

Fatty acid profiles of livers from selected marine fish species

Fish livers (FLs) constitute a rich and underexploited source of long-chain polyunsaturated fatty acids (LCPUFAs). Unfortunately, FLs are usually discarded when fish are processed in industrial factories for human consumption, thus the nutritional possibilities of LCPUFAs of FLs is wasted. Nevertheless, these organs might be used as a cheaper source of LCPUFAs, such as eicosapentaenoic (EPA, 20:5 n-3), docosahexaenoic (DHA, 22:6 n-3) and arachidonic acids (AA, 20:4 n-6). In the present work, the FA profiles of FLs of 12 fish species commonly consumed in southern Spain have been determined. The output of the analyses showed that the total FA in FLs ranged between 10.8% in European anchovy to 70.0% in great weaver. FLs from shortfin mako yielded the most unsaturated oil, showing also the higher amount of LCPUFAs (51.4%) and n-3 LCPUFAs (46.3%). FLs from great weever and European anchovy were characterized by a high LCPUFA content. All species show a good n-3/ n-6 ratio, with blue whiting (10.2) at the top of the range. Saturated FAs (SFAs) reached the highest amounts in European pilchard (35.8%) and axillary seabream (35.5%), while Mediterranean hake showed the higher amounts of monounsaturated FAs (MUFAs) (50.2%), although LCPUFA content was also noticeable in this species. A remarkable characteristic of FLs confirmed in this work is that this organ constitutes a rich source of n-3 LCPUFA, especially of EPA and DHA.

Age, growth and reproduction of the axillary seabream, Pagellus acarne, in the Atlantic and Mediterranean waters off southern Spain

The biology, growth and reproduction of the axillary seabream, Pagellus acarne, was studied based on data obtained from the catches of the Andalusia commercial fleet operating off the coasts of southern Spain from October 2003 to September 2004. The axillary seabream had a very wide depth distribution, appearing from the surface down to 500 m depth. The length–weight relationship was given by TW = 0.0048 TL3.3207 (R2 = 0.98) (TW = total weight; TL = total length) for all fish from the Gulf of Cadiz and TW = 0.0093 TL3.1132 (R2 = 0.94) for all fish from the Alboran Sea. The proportion of females to males increases as length increases in both populations and the species is characterized by protandric hermaphroditism. Spawning males were present almost throughout the year although higher percentages were observed in spring and early summer. In females, the spawning period occurred mainly in spring. In both areas, the mean size at first maturity for males was smaller than for females. The mean lengths at first maturity were 18.04 cm for males and 21.7 cm for females from the Gulf of Cadiz, and 17.7 cm and 20.1 cm for males and females from the Alboran Sea, respectively. The average total fecundity was estimated at 290,070 and 173,509 oocytes for Atlantic and Mediterranean individuals, respectively. The parameters of the von Bertalanffy growth model were estimated by age readings of the 247 sagitta collected. Two rings, one opaque and one hyaline, were laid down each year on the otoliths. The opaque zone was formed during spring and summer and the hyaline one during the remaining months of the year. The relationship between otolith radius and total length of the fish was described by the equation: TL = 27.7 OR – 1.8 (r = 0.96) (where OR = otolith radius). The parameters of the fitted Von Bertalanffy growth equation were L∞ = 31.65 cm, k = 0.21 yr−1 in the Gulf of Cadiz and L∞ = 32.14 cm, k = 0.17 yr−1 in the Alboran Sea.

Selectivity of diamond (PA) and square (PE) mesh codends for commercially important fish species in the Antalya Bay, eastern Mediterranean

Summary Size selectivity of the 40 mm nominal polyethylene (PE) square mesh codend and the 44 mm nominal polyamide (PA) diamond mesh codend were determined under commercial conditions in the demersal trawl fishery. Data were collected using the covered codend technique and analyzed by logistic equation with a maximum likelihood method. Changing the mesh from a 44 mm PA diamond to a 40 mm PE square increased the mean retention lengths (L50s) of red mullet (Mullus barbatus), picarel (Spicara maena) and bogue (Boops boops) and decreased the selection ranges (SR) for common pandora (Pagellus erythrinus). For large-eye dentex (Dentex macrophthalmus) and axillary sea bream (Pagellus acarne) mean L50 and SR values were 9.6 and 11.8, and 2.4 and 2.4 cm, respectively, only in the DM44PA codend. For golden banded goatfish (Upeneus moluccensis) values for SM40PE were only 15.0 and 2.7 cm, respectively. Results showed that the 40 mm PE square mesh codend provided higher selectivity for most of the Mediterranean fishes. The results also showed that regulating mesh size and requiring square mesh openings during trawling is essential for the release of immature individuals. This practice will result in a reduction in overfishing and permit recovery of overfished stocks.

Feeding habits of <i>Pagellus acarne</i> (Sparidae) in the Gulf of Tunis, central Mediterranean

The feeding habits of the axillary seabream, Pagellus acarne (Risso, 1810), from the Gulf of Tunis were investigated in relation to season, sex and fish size (juveniles TL < 14.5 cm and adults TL ≥ 14.5 cm). A total of 536 specimens (males, females, unsexed and hermaphroditic), ranging between 11.0 and 25.2 cm TL, were collected with trammel nets from June 2005 to July 2006. Their stomach contents were analysed. Of the total number of examined stomachs, 279 stomachs were empty (Vacuity index, VI = 52%). The VI did not reveal significant seasonal differences when all of the specimens were analysed together; however, significant seasonal variations were observed for females. The diet of the axillary seabream was composed of 36 different prey species. The most important prey were Arthropoda, Mollusca and Echinodermata. Both the dietary indices and the Spearman’s coefficient of correlation indicated seasonal variations in the diet. The diet was more diversified in adults than in juveniles. The axillary seabream fed on a wide range of prey items, endofauna and nekton, and can be considered a carnivorous and euryphagous predator.

Gill net and trammel net selectivity in the northern Aegean Sea, Turkey

Fishing trials were carried out with gill nets and trammel nets in the northern Aegean Sea from March 2004 to February 2005. Four different mesh sizes for the gill nets and the inner panel of trammel nets (16, 18, 20 and 22 mm bar length) were used. Selectivity parameters for the five most economically important species, bogue (Boops boops), annular sea bream (Diplodus annularis), striped red mullet (Mullus surmuletus), axillary sea bream (Pagellus acarne) and blotched picarel (Spicara maena), caught by the two gears were estimated. The SELECT method was used to estimate the selectivity parameters of a variety of models. Catch composition and catch proportion of several species were different in gill and trammel nets. The length frequency distributions of the species caught by the two gears were significantly different. The bi-modal model selectivity curve gave the best fit for gill net and trammel net data, and there was little difference between the modal lengths of these nets. However, a clear difference was found in catching efficiency. The highest catch rates were obtained with the trammel net. Given that many discard species and small fish are caught by gill nets and trammel nets with a mesh size of 16 mm, it is clear that these nets are not appropriate for fisheries. Consequently, the best mesh size for multispecies fisheries is 18 mm. This mesh size will considerably reduce the numbers of small sized individuals and discard species in the catch.

Trawl codend design (44 mm diamond PE mesh) and the effect on selectivity forPagellus erythrinusandPagellus acarne, two species with different morphometrics

Summary The effects of different body shapes on size selectivity were analysed. Relationships between total length and fork length, height, width and girth were estimated and the selectivity parameters of a 44 mm PE diamond mesh codend determined for common pandora (Pagellus erythrinus) and axillary sea bream (Pagellus acarne). Two data sets were collected during demersal trawl trials carried out in Izmir Bay (Aegean Sea) between May 1996 and February 1997. Regression analyses were used to determine the relationships between total length and other measured dimensions of the species. However, selectivity parameters were estimated from pooled data by using the logistic equation with the maximum likelihood method. Fork length, height, width and girth were found to increase linearly with total length for both species (R2 > 0.90, except TL–W for axillary sea bream, 0.76). Ratios of average body thickness (W/H) were 0.45 (±0.002) for common pandora and 0.52 (±0.002) for axillary sea bream. L50 and SR values were found as 12.4 (±0.44) and 2.2 (±0.51) from the eight valid hauls for common pandora and as 13.6 (±0.13) and 1.9 (±0.26) from the three valid hauls for axillary sea bream, respectively. The difference between the size selectivity of the two species in the same family can be explained by the body shape and fish behaviour distinctions.

Gill-net selectivity off the Portuguese western coast

Abstract Fishing with experimental gill-nets was carried out during 1994 and 1995 off the western coast of Portugal, using mesh sizes between 40 and 90 mm. Most sets were concentrated in the region between Setubal and Lisbon in shallow waters up to 100 m, with about 1/4 being carried out at greater depths. A total of 88 species were captured over the 2 years, of which the majority had small or no commercial value. The most important commercial species (hake, Merluccius merluccius, pouting, Trisopterus luscus, axillary seabream, Pagellus acarne, red mullet, Mullus surmuletus, and horse mackerel, Trachurus trachurus) accounted for about 12% of the catch weight in the 40 mm mesh panels, between 32 and 44% for mesh panels ranging between 60 and 80 mm, and 70% in the 90 mm mesh panels. The estimation of selectivity was carried out for the latter five species and also for the dogfish, Scyliorhinus canicula, wedge sole, Dicologlossa cuneata, and spotted flounder, Citharus linguatula, applying the SELECT method to the data pooled over both years. In the case of hake, pouting and dogfish, sufficient data were available to estimate selectivity on a yearly basis. Four different uni-modal and a bi-modal (bi-normal) models were fitted, with the bi-normal always providing the best fit as given by the smallest value of the ratio deviance/degrees-of-freedom. The exception was the wedge sole where the bi-normal model did not converge and the gamma was the unimodal model providing the best fit. The 40 mm mesh panels mostly retained species of low or no commercial value and undersized hake and pouting. Mesh size panels of 60, 70 and 80 mm proved to be the most efficient in catching the commercially valuable species over the length range available, with virtually no catch of undersized fish. The 90 mm panels retained mainly valuable species, but the overall catches were poor, with the exception of the axillary seabream. These results highlight the difficulties of managing multispecies fisheries based only on mesh size, since the optimal mesh varies considerably among the target species.

Weight-length relationships for 46 fish species of the Portuguese west coast

Weight–length (W–L) relationships were estimated for 46 species of fish captured off the western Portuguese coast between April 1994 and September 1995. The best-represented family was Scyliorhinidae (2677 fishes), followed by Gadidae (1871), Sparidae (1682) and Merlucciidae (1108). The estimates for the parameter b of the W–L relationship (W = aLb) ranged between 2.171 and 3.873, with a median of 3.124. Significant variations in b were found at seasonal level for striped red mullet (Mullus surmuletus), axillary seabream (Pagellus acarne), greater weever (Trachinus draco) and the sardine (Sardina pilchardus), at the regional level for Atlantic mackerel (Scomber scombrus), and between sexes for the small-spotted dogfish (Scyliorhinus canicula).

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.

Selectivity of diamond and square mesh cod ends for horse mackerel (&lt;i&gt;Trachurus trachurus&lt;/i&gt;), European hake (&lt;i&gt;Merluccius merluccius&lt;/i&gt;) and axillary seabream (&lt;i&gt;Pagellus acarne&lt;/i&gt;) in the shallow groundfish assemblage off the south-west coast of Portugal

The effects of an increase in cod end mesh size from 65 to 70 and 80 mm and a change of mesh configuration from 65 mm diamond to 65 mm square mesh on the size selectivity of horse mackerel (Trachurus trachurus), hake (Merluccius merluccius) and axillary seabream (Pagellus acarne) of the shallow groundfish assemblage off the Portuguese southwest coast were evaluated. The increase in mesh size had a small but significant effect on size selectivity for the three species, while the change in mesh configuration led to a much more pronounced increase in the selectivity parameters. For horse mackerel, the L50 estimates ranged from 14.4 to 16.0 cm in the diamond mesh cod ends-values that are close to the minimum landing size of 15 cm. For hake, L50 of 17.0 and 18.3 cm were estimated for the 70 and 80 mm diamond cod ends respectively, while for the axillary seabream the L50 estimated was 13.9 cm for the 80 mm diamond mesh cod end. These values are well below the minimum landing sizes of 27 and 18 cm for these species. The corresponding estimates in the square mesh cod end were 21.9, 32.4 and 19.6 cm, with the loss of a high percentage (76%) of horse mackerel above the minimum landing size. For all the cod ends tested, the observed retention was presented as a function of maximum girth/mesh perimeter, which allowed a better understanding of the selection process for the species in study. Selectivity estimates for horse mackerel and hake were also compared to those obtained by Campos et al. (2003) for the same species in 1993 off the south coast, where they are captured as a by-catch in the crustacean fishery.

Reproduction, age, growth and mortality of axillary seabream, Pagellus acarne (Sparidae), from the Canarian archipelago

Axillary seabream Pagellus acarne (Risso 1826) caught off the Canary Islands from January 1991 to December 1994 were studied. The length range of the catches was between 11 and 31 cm, with a modal distribution between 17 and 21 cm. The overall ratio of males to females was 1:1.74. Males were observed up to a length of 24 cm. Hermaphrodites were recorded at lengths between 15 and 23 cm. The species was characterized by protandric hermaphroditism. The reproductive season extended from October to March, with a peak in spawning activity in December–January. The size at sexual maturity was 15.8 cm total length (2 years old) for males and 19.4 cm total length (3 years old) for females. The total length–total weight relationship for the entire population is described by the parameters a = 0.0068, and b = 3.2401. Otolith age readings showed that the population exploited consisted of 10 age groups (1–10 years), including a very high proportion of individuals between 1 and 4 years old. The von Bertalanffy growth parameters for all individuals were L∞ = 32.98 cm, k = 0.22 years−1, and t0 = −0.87 years. Males grew comparatively slower than females. The instantaneous rates of mortality for all fish were Z = 0.96 years−1, M = 0.30 years−1, and F = 0.66 years−1. The exploitation ratio and the length at first capture were, respectively, E = 0.69 and LC50 = 16.1 cm. The stock is overexploited, therefore measures such as closed seasons or changes in fishing patterns would be desirable to safeguard the spawning stock and recruits.

Cod-end selectivities of a modified bottom trawl for three fish species in the Aegean Sea

Recently, the catch per unit effort of conventional bottom otter trawl nets used in the Aegean Sea has decreased and the mean body length of the major species has become smaller. The reason may be partly the poor selectivity of conventional trawl nets. It may be possible to modify trawl net design to improve selection and protect demersal fish stocks. This study presents selectivity results for the modified design. Cod-end selectivity of red mullet ( Mullus barbatus L.), annular sea bream ( Diplodus annularis L.) and axillary sea bream ( Pagellus acarne Risso) were measured using the hooped covered cod-end method. Cod-end mesh selectivity experiments were carried out using 36, 40, 44 and 48 mm diamond and square mesh cod-ends both in Turkish and international waters of the Aegean Sea in 1995 on board R/V “Egesüf”. The cover mesh size was 24 mm. A total of 85 successful tows were made, the raw data were assessed haul by haul and the valid hauls for each cod-end were combined. The selection of cod-ends was found from the linear logistic function and the selection curves and parameters were derived from these combined data by the maximum likelihood method. The square mesh cod-ends (36, 40 and 44 mm) improved selectivity for red mullet. Fifty percent retention length and selection factors were higher for square mesh cod-ends than diamond mesh cod-ends. However, this did not apply to annular sea bream or axillary sea bream. For these species, it was found that there was no significant difference between diamond and square mesh cod-ends and the diamond mesh cod-ends even gave a slightly higher 50% retention length and selection factor than square mesh cod-ends for some mesh sizes. This result may be explained by the different body shapes and behaviour of the individual species.

Aspects of the biology and gillnet selectivity of the axillary seabream ( Pagellus acarne, Risso) and common pandora ( Pagellus erythrinus, Linnaeus) from the Algarve (south Portugal)

Two species of seabreams, Pagellus acarne and Pagellus erythrinus, from the Algarve coast (south Portugal) were studied to obtain information on these fisheries. This study presents results on first maturity, length-weight relationships and gillnet selectivity curves, which may be used to provide a scientific basis for management proposals. Spawning lasts from May to August, and length at first maturity was 20.95 cm for P. acarne and 18.03 cm for Pagellus erythrinus. Males reached first maturity at smaller lengths than females. The relationships between length and weight were W = 0.0085TL 3.153 for P. acarne and W = 0.0189TL 2.881 for P. erythrinus. The Sechin method was used to determine gillnet selectivity curves. The estimated selectivity curves correspond closely to the catch curves, but were narrower. P. acarne will be caught in the following length ranges: 15–25 cm, 18–27 cm and 20–29 cm, and P. erythrinus in the length ranges 15–25 cm, 16–27 cm and 19–30 cm, respectively, by the 60 mm, 70 mm and 80 mm mesh sizes.