Pedro G. Lino

Weight-length relationships for selected fish species of the small-scale demersal fisheries of the south and south-west coast of Portugal

Abstract Weight-length relationships were estimated for 31 fish species from the south and south-west coasts of Portugal. These species, which are mainly sea breams (Sparidae), dominate the catches of the main fixed gears used in this region and account for more than 50% and 40% of the total fish landings by weight and by value.

Species and size selectivity in a 'red' sea bream longline 'metier' in the Algarve (southern Portugal)

A longline ‘metier’ using small hooks for ‘red’ sea breams (Pagellus acarne and Pagellus erythrinus) in the Algarve (south of Portugal) was studied. Experimental longlining was carried out with three sizes of “Mustad” round bend, flatted, spade end Quality 2316 DT hooks (numbers 11, 13 and 15) and two types of bait: razor shell (Ensis siliqua) and mud shrimp (Upogebia pusilla). A total of 3 328 fish and at least 36 species were caught with 33 600 hooks fished in 28 longline sets. Five species of sea breams (Sparidae) accounted for 79% of the catch: Pagellus acarne, Pagellus erythrinus, Diplodus vulgaris, Spondyliosoma cantharus, and Boops boops. High catch rates of 20–30 fish per 100 hooks were made in a number of 1 200 hook longline sets, with total catch weights of 40 to more than 60 kg per set. In general, the smallest hook (number 15) had the highest catch rate. Bait type did not significantly affect the catch size distributions. Although more fish were caught with the razor shell bait, higher catch rates of ‘red’ sea breams were obtained with mud shrimp. Catch rates were also affected by the location of the fishing grounds and the time of the set, with the highest catch rates obtained when the longline was set within two hours before sunrise. A wide size range was caught for each species, with highly overlapped catch size frequency distributions for the three hook sizes used. Except for Spondyliosoma cantharus, few illegal-sized fish were caught, even with the smallest hook. The logistic model fitted by maximum likelihood was used to describe hook selectivity for Diplodus vulgaris, Pagellus acarne, Pagellus erythrinus, and Spondyliosoma cantharus.

Age and growth, maturity, mortality and yield-per-recruit for two banded bream (Diplodus vulgaris Geoffr.) from the south coast of Portugal

The 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 (Lc 50 = 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.

Comparative Behavior of Wild and Hatchery Reared White Sea Bream (Diplodus sargus) Released on Artificial Reefs Off the Algarve (Southern Portugal)

Three hatchery produced and reared (HPR) and five wild white sea bream (Diplodus sargus) were double tagged with Vemco V8SC-2L acoustic transmitters and Floy Tag T-bar anchor tags, and released on artificial reefs located near a natural reef off the southern coast of Portugal. Passive telemetry was used to monitor movements of the white sea bream over a nine week period from April to June 2007. Differences in behavior at release, habitat association (artificial vs. natural reef), and in daily movements were registered. Wild fish moved from one habitat to the other with increased preference for the artificial habitat during the day, whereas HPR fish showed no site fidelity or consistent daily movement pattern and left the release site soon after release. Comparison of Minimum Convex Polygon (MCP) showed a higher area usage by wild fish. This experiment shows that these artificial reefs are used on a daily basis by wild white sea bream but apparently are not optimal release locations for hatchery produced white sea bream.

Genetic differences between wild and hatchery populations of Diplodus sargus and D. vulgaris inferred from RAPD markers: implications for production and restocking programs design

Restocking and stock enhancement programs are now recognized as an important tool for the management of fishery resources. It is important, however, to have an adequate knowledge on the genetic population structure of both the released stock and the wild population before carrying out such programs. In this study, random amplified polymorphic DNA (RAPD) markers were applied to assess genetic diversity and population structure of wild and hatchery populations of the white seabreamDiplodus sargus and the common two-banded seabreamD. vulgaris (Sparidae). The estimated values for intrapopulation genetic variation, measured using the percentage of polymorphic loci (%P), Shannon indexH’, and Nei’s gene diversity (h), showed high values for all populations. The percentage of genetic variation withinD. sargus andD. vulgaris populations, based on coefficient of gene differentiation, reached 82.5% and 90% of the total genetic variation, respectively. An undeniable decrease in genetic variation was found in both hatchery populations, particularly inD. sargus, compared to the wild ones. However, the high values of variation within all populations and the low levels of genetic variation among populations did not indicate inbreeding or depression effects, thus indicating a fairly proper hatchery management. Nevertheless, the results of this study highlight the importance of monitoring the genetic variation of hatchery populations, particularly those to be used in restocking programs. The creation of a genetic baseline database will contribute to a more efficient conservation management and to the design of genetically sustainable restocking programs.

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

A bica, Pagellus erythrinus, e uma especie comercialmente importante para as pescarias costeiras do norte e centro este Atlântico. A idade, crescimento e aspectos reprodutivos da populacao que ocorre no sul de Portugal foram estudados atraves da analise de 386 exemplares com comprimentos totais (TL) entre 12.0 e 44.8 cm. A idade foi estimada pela contagem de bandas de crescimento nos otolitos e verificada pela analise do incremento marginal, tendo-se observado exemplares entre os 1 e 21 anos. A curva de crescimento de von Bertalanffy foi o modelo mais adequado para explicar o crescimento desta especie, tendo estimado Linf = 47.14 cm TL, k = 0.084 ano-1 e t0 = - 4.42 ano. As gonadas foram analisadas macroscopicamente ao longo do periodo de um ano e determinou-se que a desova ocorre entre Marco e Julho. A primeira maturacao dos machos ocorre aos 17.58 cm TL e 1.15 anos enquanto as femeas maturam com tamanhos (17.29 cm TL) e idades (1.04 anos) ligeiramente menores. Os resultados apresentados sao importantes para a comparacao desta populacao com populacoes de outras regioes, assim como para a comparacao com estudos futuros, para a determinacao de eventuais alteracoes nos parâmetros populacionais ao longo do tempo.

Northernmost record of Kyphosus sectator (Osteichthyes: Perciformes: Kyphosidae) in the north-eastern Atlantic

This note reports the main morphometric and meristic parameters of a male Bermuda sea chub (khyphosus sectator) caught off the Algarve coast (southern Portugal). This is the first occurrence of this tropical fish species in Portuguese continental waters, and the second and northernmost capture ever reported for the north-eastern Atlantic.

Age and growth, mortality and reproduction of the striped sea bream, Lithognathus mormyrus Linnaeus 1758, from the south coast of Portugal (Algarve)

Abstract 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.