By-catch and discarding practices in five Algarve (southern Portugal) metiers

The catches and discards of trawlers, seiners and trammel netters were studied in the Algarve (southern Portugal) using observers onboard commercial fishing vessels. Species diversity was high, with 236 species recorded as occasionally, frequently or regularly discarded. Mean discard rates per trip were 0.13, 0.20, 0.27, 0.62 and 0.70, respectively, for trammel nets, demersal purse seines, pelagic purse seines, fish trawls and crustacean trawls, with high variability in terms of discard volume and discard rate, This was especially so for se ncrs where from 0 to 100% of the total catch might be discarded. No significant relationships were found between discard quantity or discard rate and characteristics of the fishing vessels sampled within each metier (total length, TAB, hp, kW). Based on the above discard rates and the official landings, it was estimated that in 1996, Algarve trawlers discarded 9000-13000 tonnes (t) while seiners discarded 5500-8200 t. Discarding practices in these fisheries are reviewed and the reasons for discarding are presented by species and metier basis. The results support the need for more studies on the factors contributing to discarding, variability in discard quantities and rates, the fate of discards and their importance to the marine ecosystem, and on ways of reducing by-catch and discarding in these fisheries.

Effect of light-sticks and electralunie attractors on surface-longline catches of swordfish (Xiphias gladius, Linnaeus, 1959) in the southwest equatorial Atlantic

Two experimental fishing trials were carried out off the coast of Pernambuco, Brazil, in 1999 and 2001, using a small artisanal longliner. In experiment 1, six-hook baskets with three chemical light-sticks on alternating hooks had significantly higher catch rates than those with zero or with a light-stick on every hook, with most swordfish accounted for by hooks with light-sticks. Analysis of the data from experiment 2 showed no significant difference between electralume attractors, consisting of AA lithium batteries protected by a solid cover and light-sticks that produce a fluorescent light when two chemical products are mixed. Significant differences were detected in mean CPUE by size class, with most swordfish belonging to class 'b' (125-170 cm lower jaw to fork length (LJFL)). No differences, however, were found for swordfish catches in classes 'a' (< 125 cm LJFL) and V, and no evidence was found of interaction between the two factors (attractor and size class). Although there was no significant difference between the total length-frequency distributions of swordfish caught with light-sticks and electralume attractors, signibcant differences were found for fish smaller than 125 cm LJFL, with electralume catches consisting of smaller swordfish than those of gear using light-sticks. (c) 2004 Elsevier B.V. All rights reserved.

Feeding habits of the deep-snouted pipefish Syngnathus typhle in a temperate coastal lagoon

Feeding habits of Syngnathus typhle were determined based on monthly sampling during experimental fishing in a coastal lagoon (Ria Formosa, South Portugal) from April 2004 to May 2002. The gut contents of 856 individuals were analysed and quantified with numerical and gravimetric methods, as well as with some complementary indices and measures (vacuity, fullness and relative importance). In this study, this species fed mainly on Copepoda, Mysidacea, small caridean grass shrimps (Hippolytidae and Palaemonidae) and small fishes (Gobiidae) and to a lesser degree on other small invertebrates. No significant differences were found between the diets of males and females. However, significant differences in the fullness indexes of both sexes were observed during the reproductive period. Significant differences in the diet among seasons were also verified but no seasonal trends were discovered. Snout length showed a linear increase with growth while mouth area and total length displayed an allometric relation. Mouth shape varied between an ellipse and an almost perfect circle. The increase in mouth area and snout length as S. typhle grows contributed to the observed ontogenic diet shift with specimens smaller than 10 cm feeding almost exclusively on Copepoda, medium sized specimens feeding mainly on Hippolytidae and Mysidacea, while larger specimens preyed on Hippolytidae, Palaemonidae and Gobiidae. Prey size generally increased with size of S. typhle. (c) 2007 Elsevier Ltd. All rights reserved.

Feeding habits of the velvet belly lanternshark Etmopterus spinax (Chondrichthyes : Etmopteridae) off the Algarve, southern Portugal

Etmopterus spinax is one of the most abundant predators of the upper continental slope off the Algarve (southern Portugal), where it is captured in large quantities in deep-water fisheries. The feeding habits of E. spinax off the Algarve were investigated through the analysis of stomach contents of 376 individuals. Prey composition was described and maturity, sex and size related variations in the diet analysed. The overall diet of E. spinax suggested a fairly generalized benthopelagic foraging behaviour primarily tuned to pelagic macroplankton/microneckton, teleost fish and cephalopods. Sex and maturity related differences in the diet were not significant. Two main ontogenic diet shifts were observed at about 17 and 28 cm total length. Small and medium sized immature sharks had a diet dominated by eurybathic crustaceans, chiefly Meganyctiphanes norvegica and Pasiphaea sivado. Larger individuals consumed more teleosts and cephalopods, in part associated with scavenging as a new feeding strategy. With increasing shark size the diet diversified both in terms of resources exploited and prey size.

Gill net selectivity for European hake Merluccius merluccius from southern Portugal: implications for fishery management

A study of European hake Merluccius merluccius gill net selectivity was undertaken off the Algarve (Southern Portugal), between 1999 and 2001. Four nominal mesh sizes (70, 80, 90 and 100 mm) were used in fishing trials and the 'share each length class catch total' (SELECT) method was used to fit gill net selectivity curves. Hake were caught in the same size range by all mesh sizes, between 17 and 65 cm total length. While most fishes were wedged, significant and similar proportions were entangled in all mesh sizes, contributing to the wide size range, and in some cases, bimodal shape of catch size frequency distributions. Insignificant numbers of undersized hake were caught, with most catches consisting of mature female fish. Catch rates decreased sharply with increasing mesh size. The bimodal model gave the best fit for hake that were wedged, with estimated modal lengths of 40.1, 46.7 and 51.0 cm for the 70, 80 and 90 mm nominal mesh sizes, respectively. The high catch per unit effort of the smallest mesh size, with most fish caught being female, together with the fact that the modal length of the fitted selectivity curve is well below the size at maturity for hake in Portuguese waters, suggests that the 80 mm nominal mesh size is more appropriate for ensuring resource sustainability.

Life history of the common pandora, Pagellus erythrinus (Linnaeus, 1758) (Actinopterygii: Sparidae) from southern Portugal

The common pandora, Pagellus erythrinus, is a commercially important seabream for coastal fisheries in the north and central eastern Atlantic. Age, growth and reproductive aspects of the southern Portuguese population were estimated by analysing 386 specimens ranging in total length (TL) from 12.0 to 44.8 cm. Ages were estimated by counting growth bands on otoliths and verified by marginal increment analysis, with specimens ranging in age from 1 to 21 years. The von Bertalanffy growth function was selected as the most adequate model to fit this species' growth, with the estimated parameters being L-inf = 47.14 cm TL, k = 0.084 year(-1) and t(0) = - 4.42 year. The gonads were analyzed macroscopically over a one-year period and the reproductive spawning season found to occur from March to July. The length at first maturity for males occurs at 17.58 cm TL and 1.15 years while females mature at slightly smaller sizes (17.29 cm TL) and younger ages (1.04 years). The results presented in this study are important for comparing this population's parameters with those of other populations of the same species occurring in other areas, as well as for future studies, for assessing eventual changes in population parameters over time.

Reproductive aspects of the undulate ray, Raja undulata, from the south coast of Portugal

The maturity of the undulate ray, Raja undulata, one of the most important by-catch elasmobranch species captured in south Portugal, was studied for the first time. Females ranged in total length (TL) from 19.4 to 88.2 cm and males from 23.0 to 83.2 cm. The gonadosomatic index for females was higher during the winter, meaning that this species reproduces during this season. Females matured at significantly larger sizes and older ages than males, with 50% of the females mature at 76.2 cm TL at an age of 8.98 years while 50% maturity for males was achieved at 73.6 cm TL and 7.66 years. Females were mature at 86.3% of the maximum observed size and 69.1% of the maximum observed age while males matured at 88.5% of the maximum observed size and 63.8% of the maximum observed age, making this a very late maturing species, with important consequences in terms of fisheries management and conservation. (c) 2006 Elsevier B.V. All rights reserved.

Reproductive biology of the blackmouth catshark, Galeus melastomus (Chondrichthyes : Scyliorhinidae) off the south coast of Portugal

The reproductive biology of 1045 female (9.5-67 cm (total length(TL)) and 1007 male (9.4-64.3 cm TL) blackmouth catsharks, Galeus melastomus, was investigated. The sharks were caught off southern Portugal by bottom crustacean trawlers at depths from 209 to 754 m. The sex ratio was 1:1, and this species is sexually dimorphic with males approaching maturity at smaller size than females. Sexual segregation appears to be given for the stork within the study area. Sexual maturity was reached at a total length above 49 cm in males and above 56 cm in females. Mating and egg-deposition take place all year round, with two reproductive peaks of activity, in winter and summer. Egg capsules are, on average, 54 mm long and 21 mm wide, with a maximum of 63 x 25 mm encountered. Morphometric measurements of claspers, testes, ovaries, and oviducal glands were suitable for determining sexual maturity of blackmouth catshark.

Site fidelity and movements of gilthead sea bream (Sparus aurata) in a coastal lagoon (Ria Formosa, Portugal)

Short-time site fidelity and movements of gilthead sea bream (Sparus aurata) in a coastal lagoon were determined using passive acoustic telemetry. Nine fish, ranging from 20.1 to 32.5 cm total length, were surgically implanted with acoustic transmitters and monitored for up to 179 days. Minimum convex polygon areas ranged from 18,698.6 m(2) to 352,711.9 m(2). Home range sizes were small, with individuals using core areas on a daily basis. However, these core areas shifted within the study site over time towards the opening to the sea. Two different diel behaviors were recorded, with some individuals more active at night and others during day time. Some individuals also demonstrated homing abilities, returning to the capture site after being released more than 4 km away. (C) 2008 Elsevier Ltd. All rights reserved.

Size selectivity of diamond and square mesh cod ends for four by-catch species in the crustacean fishery off the Portuguese south coast

The effects of an increase in cod end mesh size from 55 to 60 and 70 mm and a change of mesh configuration from 55 mm diamond to 55 turn square mesh on the size selectivity of four by-catch species (the red shrimp Aristeus antennatus, the European hake Merluccius merluccius, the horse mackerel Trachurus trachurus and the blue whiting Micromesistius poutassou) commonly captured in the crustacean fishery off the Portuguese south coast, were evaluated. Selectivity parameters for blue whiting, the most abundant species in the catches, were estimated taking into account between-haul variation, while for the remaining species, captured in much lower quantities, the selectivity estimates were based on pooled data by length class for all hauls within the same cod end. Length at 50% retention, L-50, was found to increase with mesh size and with the change in mesh configuration for all the studied species. For blue whiting trawling depth and cod end catch were found to play a role in between-haul variation by increasing L-50 as well. The results suggest that an increase in the current minimum mesh size of 55-70 mm would be advisable to be compatible with the minimum landing sizes (MLSs) of 29 mm carapace length and 27 cm total length for red shrimp and hake, respectively, while it would greatly reduce the amount of discards, particularly those for blue whiting, that accounted for approximately 50% of the total catch weight. Horse mackerel was the only species for which the use of a larger mesh size would result in a significant escapement of individuals above the MLS of 15 cm. (C) 2002 Elsevier Science B.V. All rights reserved.

The reproductive biology of Spondyliosoma cantharus (L.) from the SW Coast of Portugal

The study of Spondyliosoma cantharus (L.) reproduction was carried out within the framework of a project on the Fisheries resources of the south-west coast of Portugal, and was based on the analysis of the spawning season, gonad maturation, size-at-maturity, fecundity, and hermaphroditism. Spawning took place from February to April, peaking in March. Analysis of the sex ratio by size class and season showed that females were more abundant throughout the year (M/F=0.57) and in the smaller size classes. Overall size at first maturity (L-50) was 20.10 cm total length (TL), with a significant difference between males (22.41 cm, TL) and females (19.98 cm, TL). Absolute fecundity (Fa) ranged from 37,506 to 112,074 oocytes, with a mean of 61,396. A power type relationship best described the relationships between absolute fecundity and TL (Fa = 436.27TL(1.575)), and somatic weight (Fa = 2979.7SW(0.585)). The number of oocytes/g of female somatic weight ranged from 217 to 549, with a mean of 346. The reproductive strategy of this species is characterised by protogynic hermaphroditism, as indicated by the presence of individuals in transition and of testes with vestiges of preceding ovaries associated with the significant differences in the size frequency distributions of the sexes.

The reproductive biology of the two-banded sea bream (Diplodus vulgaris) from the southwest coast of Portugal

The study of the reproduction of Diplodus vulgaris (Geoff.) as part of a base-line study of the fishery resources of the southwest coast of Portugal, was based on the analysis of the spawning season, gonad maturation, size at maturity, fecundity and hermaphroditism. The spawning season is relatively long, from December to March, with peaks in January and February. No significant differences were found either in the sex ratio (M:F = 1.01) over the year or by size. The size at first maturity (L-50) for all sexes and undetermined individuals combined was 18.33 cm total length (TL), with no significant differences between males and females. The estimated L-50 is considerably greater than the minimum legal size in Portugal of 15.0 cm. Mean absolute fecundity (F-a) was 131 127 oocytes, ranging from 31 523 to 250 608. The relationship between absolute fecundity and total length (TL) (F-a = 25 398 TL-484 426) and somatic weight (SW) (F-a = 878.8SW-71 416) was of the linear type. The mean number of oocytes per gram of somatic weight was 526, ranging from 194 to 887. The reproductive strategy of this species is characterized by a rudimentary hermaphroditism with possible protandry, as evidenced by the existence of individuals in sexual transition.

Age and growth of the bigeye thresher shark, Alopias superciliosus, from the pelagic longline fisheries in the tropical northeastern Atlantic Ocean, determined by vertebral band counts

The bigeye thresher, Alopias supercilious, is commonly caught as bycatch in pelagic longline fisheries targeting swordfish. Little information is yet available on the biology of this species, however. As part of an ongoing study, observers sent aboard fishing vessels have been collecting set of information that includes samples of vertebrae, with the aim of investigating age and growth of A. supercilious. A total of 117 specimens were sampled between September 2008 and October 2009 in the tropical northeastern Atlantic, with specimens ranging from 101 to 242 cm fork length (FL) (176 to 407 cm total length). The A. supercilious vertebrae were generally difficult to read, mainly because they were poorly calcified, which is typical of Lamniformes sharks. Preliminary trials were carried out to determine the most efficient band enhancement technique for this species, in which crystal violet section staining was found to be the best methodology. Estimated ages in this sample ranged from 2 to 22 years for females and 1 to 17 years for males. A version of the von Bertalanffy growth model (VBGF) re-parameterised to estimate L(0), and a modified VBGF using a fixed L(0) were fitted to the data. The Akaike information criterion (AIC) was used to compare these models. The VBGF produced the best results, with the following parameters: L(inf) = 293 cm FL, k = 0.06 y(-1) and L(0) = 111 cm FL for females; L(inf) = 206 cm FL, k = 0.18 y(-1) and L(0) = 93 cm FL for males. The estimated growth coefficients confirm that A. supercilious is a slow-growing species, highlighting its vulnerability to fishing pressure. It is therefore urgent to carry out more biological research to inform fishery managers more adequately and address conservation issues.

Age and growth of bluemouth, Helicolenus dactylopterus (Delaroche, 1809) from the Azores

The age and growth of the Helicolenus dactylopterus (Delaroche, 1809) in the Azorean waters were studied using whole and sliced otolith readings. Individuals were collected during demersal surveys carried out around the Azores islands and its most important fishing banks and also from commercial landings. A total of 1024 individuals were measured, weighed and their sex was determined. Individuals ranged from 3 to 49 cm total length (TL) and their estimated ages between 0 and 32 years old. The otoliths showed the typical teleost fish pattern with alternated opaque and hyaline rings. Significant differences between sliced and whole otolith readings were found, especially after 7 years old (>25 cm TL). Sliced otoliths were found easier to read, regardless of TL or age. Comparisons with other studies for the Azores region and other areas are discussed.

Reproductive aspects of the oceanic whitetip shark, Carcharhinus longimanus (Elasmobranchii: Carcharhinidae), in the equatorial and southwestern Atlantic Ocean

The present study sought to study the reproductive biology of the oceanic whitetip shark, Carcharhinus longimanus, in the equatorial and southwestern Atlantic Ocean. A total of 234 specimens were collected as bycatch during pelagic longline fisheries targeting tunas and swordfish, between December 2003 and December 2010. The fishing area was located between latitudes 10N and 35S and longitudes 3E and 40W. Of the 234 individuals sampled, 118 were females (with sizes ranging from 81 to 227 cm TL, total length) and 116 males (ranging from 80 to 242 cm TL). The reproductive stages of the females were classed as immature, mature, preovulatory and pregnant, while males were divided into immature, maturing and mature. The size at maturity for females was estimated at 170.0 cm TL, while that for males was between 170.0 and 190.0 cm TL. Ovarian fecundity ranged from 1 to 10 follicles and uterine fecundity from 1 to 10 embryos. The reproductive cycle of this species is most likely biennial, with parturition occurring once every two years.