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Artificial reefs have been deployed along the southern coast of Portugal (Algarve) since 1990 to enhance artisanal fisheries. The objectives of this study were to: (1) describe the colonisation process; (2) assess the role of the artificial reefs in terms of juvenile recruitment and growth and as mating/spawning areas and (3) evaluate the potential of artificial reefs as near shore artisanal fishing grounds for three economically important fish species, Diplodus bellottii (Steindachner), Diplodus sargus (L.) and Diplodus vulgaris (Geoffroy Saint-Hilaire). The fish assemblages were monitored after the deployment of a large artificial reef (Faro/Ancão) in 2002. Colonisation rates for the three species were fast. Artificial reefs play a multiple role for Diplodus spp., acting as recruitment, growth and nursery areas for juveniles, and spawning/mating areas for adults, and can thus be considered essential fish habitat. Three months after deployment of the artificial reefs, exploitable biomass was 16, 29 and 8 kg per reef group, respectively, for D. bellotti, D. sargus and D. vulgaris. These results indicate that artificial reefs quickly become good fishing grounds, where suitable financial yields may be obtained by fisher. Moreover, the artificial reefs became new and alternative fishing grounds, allowing reduction of fishing effort over traditional rocky areas that are scarce along the Algarve coast. Management measures for artificial reefs, in terms of fishing strategies, are discussed. [ABSTRACT FROM AUTHOR]

Recreational shore angling in the Atlantic Ocean between Moledo and Aveiro (Portugal) was examined using roving creel surveys (March/September 2001). Cooperation was high (90% of 2310 anglers approached). At least 39 species of fish were caught at a rate of approximately 0.5 fish angler h−1. An estimated 7319 kg of Dicentrarchus labrax (L.), with 45.6% below the minimum legal size, and 2040 kg of sea breams (genus Diplodus), correspond to 5.75% and 1.19% of the commercial landings in the same geographical area, respectively. The results shed light on a number of issues relevant to integrated coastal management, including temporal and spatial distribution of fishing effort, species caught, sizes of fish, catch rates, and factors influencing catches and angler satisfaction. Whilst the results suggest that the catches of sea breams and sea bass by day-time recreational shore angling in northern Portugal are small compared with commercial fishing, other recreational activities, such as boat fishing and spear-fishing, must be assessed. [ABSTRACT FROM AUTHOR]

Summary The study of the reproduction of Diplodus vulgaris (Geoff.) as part of a base-line study of the fishery resources of the south-west 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 (L50) for all sexes and undetermined individuals combined was 18.33 cm total length (TL), with no significant differences between males and females. The estimated L50 is considerably greater than the minimum legal size in Portugal of 15.0 cm. Mean absolute fecundity (Fa) was 131 127 oocytes, ranging from 31 523 to 250 608. The relationship between absolute fecundity and total length (TL) (Fa = 25 398 TL – 484 426) and somatic weight (SW) (Fa = 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. [ABSTRACT FROM AUTHOR]

Abstract: Artificial reefs are used as management tools for coastal fisheries and ecosystems and the knowledge of habitat use and fish movements around them is necessary to understand their performance and improve their design and location. In this study wild specimens of Diplodus sargus were tagged with acoustic tags and their movements were tracked using passive acoustic telemetry. The monitored area enclosed a natural rocky reef, an adjacent artificial reef (AR) and shallower sandy bottoms. Most of the fish were close to full time residents in the monitored area. Results revealed that D. sargus use the natural reef areas on a more frequent basis than the AR. However, excursions to the adjacent AR and sandy bottoms were frequently detected, essentially during daytime. The use of acoustic telemetry allowed a better understanding of the use of artificial reef structures and its adjacent areas by wild D. sargus providing information that is helpful towards the improvement of AR design and location. [Copyright &y& Elsevier]

Abstract: The common two-banded sea bream (Diplodus vulgaris) is an important fish in the marine ecosystems of the NW Atlantic and Mediterranean. In southern Portugal it is a major fishery resource being targeted mainly by the artisanal fleets. Although there is some knowledge of the age, growth and reproductive biology of the species, information about its population structure is scarce and somewhat limited to the Mediterranean Sea. In this study the otolith elemental signatures of 90 specimens of D. vulgaris of the same age group (2+ years) and cohort collected from the important fishery regions of SW Portugal (Sesimbra, Sagres and Faro) have been analysed by inductively coupled plasma mass spectrometry (ICP-MS). Two different methodologies have been applied: solution based analysis of the whole otoliths; representative of the entire life-history prior to capture, and laser ablation analysis of otolith cores; representative of the larval and early post-settlement phase. Whole otolith comparisons utilised Sr/Ca, Ba/Ca, Mn/Ca, Li/Ca and Ni/Ca to demonstrate regional population structure. Classification accuracy rates from linear discriminant function analyses (LDFA) of whole otolith chemistry data were high for each region; Faro – 93%, Sagres – 90% and Sesimbra – 80%. Comparison of the otolith core chemistry utilised Sr/Ca, Ba/Ca, Mn/Ca and Mg/Ca and Zn/Ca. LDFA for the otolith core chemistry also achieved accurate classification for samples from Sesimbra (73%), but there was high overlap of otolith chemistry between samples from Faro and Sagres (47 and 43% classification accuracy respectively). The whole otolith results suggest that D. vulgaris are resident in the regional fishing areas during the juvenile phase. Both the core and whole otolith chemistry data supported separation of the Sesimbra fishery region from the more southern and closely associated Faro and Sagres regions for management purposes. However, while the whole otolith data indicated that the populations at Faro and Sagres likely remained separated in the juvenile stage, the otolith core chemistry data was inconclusive as to whether recruitment to these two areas was derived, or not, from different spawning areas. [Copyright &y& Elsevier]

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 (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. [Copyright &y& Elsevier]