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- Catches in ghost-fishing octopus and fish traps in the northeastern Atlantic Ocean (Algarve, Portugal)Publication . Erzini, Karim; Bentes, L.; Coelho, Rui; Lino, P. G.; Monteiro, P.; Ribeiro, J.; Gonçalves, J. M. S.Ghost fishing is the term used to describe the continued capture of fish and other living organisms after a fisherman has lost all control over the gear. Traps may be lost for a variety of reasons including theft, vandalism, abandonment, interactions with other gear, fouling on the bottom (i.e., traps and ropes are caught on rocky substrate), bad weather, and human error (Laist, 1995). Annual trap loss can be as high as 20% to 50% of fished traps in some fisheries (Al-Masroori et al., 2004). Because lost traps can continue to fish for long periods, albeit with decreasing efficiency over time (e.g., Smolowitz, 1978; Breen, 1987, 1990; Guillory, 1993), ghost fishing is a concern in fisheries worldwide.
- Potential of fisheries restocking off the Algarve coast using aquaculture produced marine fishPublication . Lino, Pedro; Santos, M. N.; Erzini, KarimThe clear decrease in fisheries landings along the Portuguese coast and in the same scale off the south coast of the Algarve prompted IPIMAR, the Portuguese fisheries institute to test recovery measures for the stocks. In addition to restrictive measures such as mesh size, fishing effort or minimum legal size, it is possible to foster stock recovery with positive measures. Having created an artificial reef along the south cost of Algarve, IPIMAR proposed to investigate the possibility of stock enhancement by releasing hatchery produced and reared fish. Since IPIMAR already had the know-how to produce several Sparidae species, namely Sparus aurata, Diplodus sargus, D. vulgaris and D. cervinus, it was possible to conduct experimental tag and release trials with these species. Although similar studies have been carried out in other countries, it is a requirement that local species are tested at the local scale. Therefore the main objective of this study was to assess the potential of restocking the Algarve coast with hatchery produced fish. In addition, there was a concern that the release of hatchery produced fish could have a negative genetic impact on the wild populations. The results of the study show that if a good management of the brood stock is carried out, there is no significant loss of genetic diversity and therefore the release of this fish will not have a negative effect on the wild populations. The results obtained through several tagging methods from conventional numbered tags to acoustic telemetry, indicate that the release of fish off this coast could have a positive impact at the local level since the selected species are able to quickly adapt to the natural environment and the dispersion occurs mainly along the South coast of the Algarve.
- Life history of the common pandora, Pagellus erythrinus (Linnaeus, 1758) (Actinopterygil: Sparidae) from southern PortugalPublication . Coelho, Rui; Bentes, Luis; Correia, Carla; Gonçalves, Jorge Manuel Santos; Lino, Pedro; Monteiro, Pedro; Ribeiro, Joaquim; Erzini, KarimThe 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.
- A comparison of monofilament gillnet and small hook longline selectivity in a multispecies artisanal fishery in the Algarve, Southern PortugalPublication . Erzini, Karim; Santos, M. N.; Monteiro, C. C.; Gonçalves, J. M. S.; Bentes, L.; Lino, Pedro G.As part of ongoing studies concerned with the small-scale fisheries of the South of Portugal, experimental fishing was carried out with monofilament gillnets and small hook longlines within the same area. Sixty-two species were caught, of which 20 were common to both gears. Pronounced differences in terms of the relative importance of different species in the catches were observed. Size selection patterns also differed, with highly overlapped hook catch distributions and few species showing evidence for size selectivity. In contrast, strong selectivity was characteristic of species which tend to be "wedged" in gillnets. Whereas smaller stretched mesh sizes (particularly 40 and 50 mm) caught significant numbers of illegal sized fish, this was minimal in the longlines. Some implications for management are discussed.
- By-catch and discarding practices in five Algarve (southern Portugal) metiersPublication . Borges, Teresa C.; Erzini, Karim; Bentes, L.; Lima Costa, Maria Emília; Gonçalves, J. M. S.; Lino, P. G.; Pais, C.; Ribeiro, J.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.
- Seasonal, tidal and diurnal changes in fish assemblages in the Ria Formosa lagoon (Portugal)Publication . Ribeiro, J.; Bentes, L.; Coelho, R.; Gonçalves, Jorge Manuel Santos; Lino, P. G.; Monteiro, P.; Erzini, KarimFish fauna were collected in two different subtidal shallow sites, seagrass and sand, using a small beam trawl in the Ria Formosa lagoon (South Portugal). Samples were taken at low and high tides, during day and night, and in each season. Fish assemblages associated with each site were significantly different, with seagrass site supporting greater fish abundance and higher number of species than sand. These site-related differences in fish assemblages were stronger than any other factor studied. Both sites showed seasonal variations in their fish assemblages, mainly because of recruitment of marine juvenile migrants during spring and summer. No significant tidal or diel changes were observed in the fish assemblages of either site, but there was a significant site-tide interaction, with higher fish abundance in seagrass at low tide. In sand, tide effect was evident only for certain species, with resident species more abundant at high tide and marine species more abundant at low tide. Within the Ria Formosa coastal lagoon, ichthyofaunal composition and structure is mainly influenced by site followed by season. (c) 2005 Elsevier Ltd. All rights reserved.
- Age and growth, mortality and reproduction of the striped sea bream, Lithognathus mormyrusLinnaeus 1758, from the south coast of Portugal (Algarve)Publication . Monteiro, Pedro; Bentes, L.; Coelho, Rui; Correia, Carla; Erzini, Karim; Lino, Pedro; Ribeiro, Joaquim; Gonçalves, J. M. S.The striped sea bream, Lithognathus mormyrus, used for this population dynamics study were obtained from longline catches and market sampling in the Algarve (south Portugal). The macroscopic analysis of the gonads and the gonad somatic index showed that the south Portuguese population of L. mormyrus spawns mainly between late spring and summer (June to August). The length at first maturity was similar for males and females and the value for both sexes combined was estimated to be 16.08 cm, corresponding to an age between 1 and 2 years. Fish age classes (0 to 13) were determined by reading growth rings on whole otoliths. Age determination was validated by marginal increment analysis. The estimated parameters of the von Bertalanffy growth equation were L∞=35.30 cm, K=0.264 and t 0= − 0.809. Mortality rates were calculated for fish captured with longlines, and the estimated parameters were M=0.356, Z=0.622 and F=0.266. From an Algarve fishery management perspective, these results suggest the need for an increase in the minimum landing size (from 15 to 17 cm), which should be beneficial for the sustainability and conservation of this species. The results also showed that fishing with longlines off the Algarve coast may allow for a sustainable use of the resource.
- An overview of the hooking mortality of elasmobranchs caught in a swordfish pelagic longline fishery in the Atlantic OceanPublication . Coelho, Rui; Fernandez-Carvalho, Joana; Lino, Pedro; Santos, Miguel N.Hooking (or “at-haulback”) fishing mortality was analysed in elasmobranchs captured by Portuguese longliners targeting swordfish in the Atlantic Ocean. Information was collected by on-board fishery observers who monitored 834 longline fishing sets between August 2008 and December 2011, and recorded information on 36,067 elasmobranch specimens from 21 different taxa. The hooking mortality proportions were species-specific, with some species having relatively high percentages of live specimens at time of haulback (e.g., blue shark, crocodile shark, pelagic stingray, manta, devil and eagle rays), while others had higher percentages of dead specimens (e.g., smooth hammerhead, silky shark, bigeye thresher). For the most captured species, logistic GLMs were carried out to compare the mortality rates between sexes, specimen sizes and the regions of operation of the fleet. The sex-specific proportions of hooking mortality were significantly different for blue and crocodile sharks, with the males of both species having higher proportions of hooking mortality than the females. Specimen size was significant for predicting the hooking mortality for blue and shortfin mako sharks: in both cases, the larger specimens had lower odds of dying due to the fishing process. There were differences in the hooking mortality depending on the region of operation of the fleet, but those differences were also species-specific. For blue and crocodile sharks, the hooking mortality was higher in the Equatorial and southern Atlantic areas (when compared to the NE Atlantic region), while the opposite was observed for the shortfin mako, with lower mortality rates in the NE tropical area compared with the other regions. The results presented in this paper can be integrated into future ecological risk assessment analysis for pelagic elasmobranchs. Furthermore, the new information can be used to evaluate the impact of recent recommendations prohibiting the retention of some vulnerable elasmobranch species.
- Age and growth, maturity, mortality and yield-per-recruit for two banded bream (Diplodus vulgaris Geoffr.) from the south coast of PortugalPublication . Gonçalves, J. M. S.; Bentes, L.; Coelho, Rui; Correia, C.; Lino, P. G.; Monteiro, P.; Ribeiro, J.; Erzini, KarimThe population dynamics parameters of Diplodus vulgaris (Sparidae) from the south and south-west coast of Portugal were studied. 1086 fishes with total lengths ranging from 3.3 to 37.9 cm were obtained from previous gear selectivity studies supplemented by market sampling and beach seining for juveniles (1992–2000). The spawning season extended from September to April and total lengths at 50% maturity were 17.27 cm for males and 17.65 cm for females. These estimated sizes were greater than the minimum legal landing size (MLS = 15 cm) and smaller than length at first capture (Lc50 = 21.68 cm) for the longline fishery. The parameters of the von Bertalanffy growth equation were: L∞ = 27.73 cm, K = 0.40 per year, t0 = −0.34 year. The instantaneous rates of total mortality (Z) and natural mortality (M) were 0.63 and 0.45 per year, respectively. Rates of fishing mortality F and exploitation E were 0.18 and 0.28 per year, respectively. Estimated parameters and the relative yield-per-recruit analysis showed that this species is not over exploited by longlines.
- Non-commercial invertebrate discards in an experimental trammel net fisheryPublication . Gonçalves, J. M. S.; Bentes, L.; Coelho, R.; Monteiro, P.; Ribeiro, J.; Correia, C.; Lino, P. G.; Erzini, KarimNon-commercial invertebrate discards in an experimental trammel net fishery were studied in relation to selectivity of the gear, depth, soak time and season. Forty experimental fishing trials were carried out over a 1-year period with six combinations of small mesh (100, 120 and 140 mm) inner and large mesh (600 and 800 mm) outer panels. On average, 43.8 +/- 12.2 (SD) (individuals 1000 m(-1) of net) of non-commercial invertebrates were discarded, accounting for 48% and 65% of the total catch and total discards by numbers, respectively. Within non-commercial invertebrates discards, the six most abundant species by number were Phallusia mammillata (Cuvier) (27.5%), Cymbium olla (L.) (13.0%), Sphaerechinus granularis (Lamarck) (11.3%), Paracentrotus lividus (Lamarck) (10.9%), Astropartus mediterraneus (Risso) (8.2%) and Astropecten aranciacus (L.) (8.1%); Echinoderms (43.1%) particularly important. The highest and lowest discard ratios were found in autumn and winter, respectively. Discards generally decreased with depth, varied considerably in relation to soak time and were not related to mesh size combinations. Trammel nets seem to be the most important gear in terms of ecological impacts on benthic invertebrates compared with other coastal fishing gears and at the depths studied (15-60 m).