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The present study reports a detailed description of the catches of cuttlefish (Sepia officinalis) in the trap fishery performed seasonally off the Algarve coast (southern Portugal). A total of 86 fishing surveys were performed during the fishing season (May-September) from 2009 to 2014, on sandy bottoms at bathymetrics ranging from 8 to 10 m depth. During the whole study period, fishing operations involved 6311 cuttlefish traps with a gear catch rate of 37% (frequency of traps with cuttlefish) and a mean of 0.9 S. officinalis caught per trap. A total of 5883 S. officinalis (1424.0 kg) were caught, being only recorded 282 dead individuals (mortality rate of 4.6%). The mean fishing yield (standardised CPUE's in number and weight) was 46.6 individuals and 11.3 kg 50 traps(-1). Overall, males (n = 3188) outnumbered females (n = 2695), producing a significant male-biased (1 M: 0.85 F) sex ratio. On average, females were significantly larger and heavier (124.4 +/- 22.9 mm ML; 253.1 +/- 148.8 g TW) than males (121.9 +/- 24.0 mm ML; 230.7 +/- 143.1 g TW). Accordingly, the length-frequency distributions displayed significant gender differences, with 89.6% of females and 85.8% of males accomplishing the MCRS (100 mm ML). This markedly seasonal, highly sustainable and low impacting small-scale fishery constitutes a locally important socio-economic activity during spring and summer. Undamaged catches and highly fresh individuals further contribute to the considerable price reached by S. officinalis caught using this artisanal fishing gear. Agência financiadora European Union (EU) Fisheries Operational Programme (MAR 2020) European Maritime and Fisheries Fund (EMFF 2014-2020) info:eu-repo/semantics/publishedVersion

The main objectives of this study were (i) to provide an updated age-length key for D. trunculus from Atlantic waters, and (ii) to evaluate population dynamics, the timing of recruitment and production parameters of the wedge clam Donax trunculus in two moderately exposed sandy beaches (the protected area of Donana National Park and the tourist destination of Isla Canela) along the littoral of Huelva (SW Spain). First an in-depth analysis of the shell and updated estimation of growth parameters of the intertidal D. trunculus population were performed between January 2014 and July 2015 using two different methods i) thin-layer cross section (TL) (ii) length-frequency distributions (LFD). Von Bertalanffy growth functions provided an asymptotic length of 46 mm (LFD) and 46.7 mm (TL) and growth constants of 0.48 (LFD) and 0.47 yr(-1) (TL) in Donana beach. In addition, several deformities as well as signs of shell repair were observed. Population dynamics analyses through length frequency distribution clarified the timing of recruitment (February-March and July). The mean annual biomass ((B) over bar) of intertidal populations of D. trunculus ranged between 3.03 (Donana) and 3.31 g ash-free dry mass (AFDW) m(-2) yr(-1) (Isla Canela). Individual production showed the highest value at 27 mm length (0.117 g AFDW m(-2) yr(-1)) and annual production (P) ranged between 3.40 (Donana) and 4.91 g (Isla Canela), resulting in renewal rate (P/(B) over bar) values between 1.03 and 1.61, respectively. The present results, together with information on environmental parameters, revealed clear differences in population dynamics and production between beaches related to the presence or absence of a protection figure. European Fisheries Fund info:eu-repo/semantics/publishedVersion

The exploitation of the common octopus Octopus vulgaris in Portugal increased 50% in the last 20 years, largely motivated by the depletion of many fish stocks. Recently, the biomass of this fishery resource sharply decreased in some areas causing serious concern among local fishermen and an effort is underway to advise on novel and sustainable management measures. In this context, the octopus pre-recruit aggregations along the Portuguese coast are identified using georeferenced fishery-independent data, from autumn and winter sampling between 1996 and 2008. The relationships between pre-recruit aggregations and several environmental variables are analyzed to characterize their essential habitats (EFH). Pre-recruits are distributed throughout the Portuguese coast aggregated in 8 distinct recruitment grounds located on the middle-shelf at 11–19 km from the coastline, which are characterized by average bottom depths of 65–110 m and are associated to major rivers and lagoon systems. Within each season pre-recruit abundance is much higher in the south region, while pre-recruit aggregations on the northwest coast showed high inter-annual and seasonal variation driven by environmental variability. The western zone adjacent to Ria Formosa lagoon (southern coast) was identified as the main recruitment ground for O. vulgaris along the Portuguese coast. This is supported by the higher abundance of pre-recruits and by the recurrence of their presence in this area over the years analyzed, both in autumn and winter. The effects of physical variables on pre-recruit abundance modelled with generalized additive models (GAM) showed important regional differences. Bottom salinity and river runoff are the environmental variables that have most impact on pre-recruit distribution and abundance on the west coast, regardless of any seasonal effects. On the other hand, temperature imposes distinct seasonal and regional limitations on pre-recruit distribution, both on the NW and S regions. Pre-recruit preferential habitat is characterized by bottom temperatures of 14 °C, salinity values around 36.0, low precipitation (average

This paper explores the evolution of productivity of the artisanal dredge fleet that operates in the south coast of Portugal. This fleet is considered to be one of the most significant in the sector, essentially due to the volume and value of its catches. In this context, the study carried out sought in first place to determine variation in productivity over a time window of 10 years (between 1995 and 2004). Secondly, it sought to distinguish the performance of local and coastal vessels comprising the chosen fleet. The performance of the five homeports in the Algarve coast was also compared. We used Malmquist indexes to measure productivity change and explored the impact of changes in stock conditions and in regulatory policies on productivity levels. During the time period analysed, the measures defined by regulatory entities included allowing the use of a new type of dredge and the establishment of fishing quotas per vessel and per species. Finally, the fishing quotas allowed for each vessel were confronted with the captures officially declared.

An experiment to study ghost fishing using a total of 27 monofilament gill nets in two trials was conducted between 2000 and 2002, approximately 6.5 miles off the city of Faro (Algarve, southern Portugal). The nets were set during spring and autumn, on a sandy-muddy fishing ground at depths between 65 and 78 m, for European hake ( Merluccius merluccius ). They were set with one end cut loose to simulate lost nets. The hake catches (size, number and biomass) and biofouling (weight) from the twine of the deliberately lost nets were monitored over time, by using grapnel equipment to “creep” for and retrieve the nets in groups of three at sequential increasing intervals. The day before each net retrieval, three control nets were set in order to evaluate the changes in the catching efficiency of the lost nets over time. Similar patterns were observed in both trials, with a sharp decrease in the nets’ catching efficiency and an increase on the biofouling. Hake catches were initially comparable to those taken in normally fished gill nets in the area, but decreased steadily over time. Biofouling was strongly associated with declines in net catching efficiency. Under the conditions experienced in the study, the maximum fishing lifetime of a “lost” gill net is 248 days, but showing negligible catches after 3 months. Based on an exponential model, we estimated that a 100 m length of gill net will catch is a maximum 87.6 hake, weighing 29.9 kg during this time. The study showed that hake “ghost fishing” represent only 0.5% of the total annual hake catches in the Algarve, and is considered to be a minor problem compared to discarding.

The use of biofouling for estimating the age of lost nets was investigated by means of net loss simulations and sequential retrieval, conducted in the Bay of Biscay (northern Spain) and off the Algarve (southern Portugal). Two trials were conducted in each location at different seasons. At both study sites, heavier colonisation was observed on the upper parts of the retrieved nets than in the bottom sections, irrespective of season. The biomass of fouling organisms was subject to geographical and seasonal variation, being considerably higher in the Algarve and throughout the spring/summer trials. Three bivalve species were selected as key species for net ageing: Anomia sp., Hiatella artica and Pteria hirundo . Bivalve abundance increased over time, until the 7th month of the trials in the Bay of Biscay and the 3rd month off the Algarve, and decreased thereafter. Analyses of the specimens’ size evolution over time indicated that the shell length of Anomia sp. could be used for ageing abandoned nets in the Bay of Biscay and that of P. hirundo off the Algarve. However, the use of these particular organisms for estimating soaking times of fishing gear is limited to a specific set of environmental conditions.

Fishermen surveys were conducted in the major fishing ports of the Algarve (southern Portugal) to investigate the reasons and extent of losses of gill and trammel nets. A total of 112 interviews were made covering both the local and coastal components of the fleet, with special attention being given to the hake metier. The inquiries showed different causes for net loss between the two fleet components. The smaller boats lost nets mainly due to rough weather, while the conflicts with other gears caused more losses to the larger boats. Most skippers attempted to recover their nets, but the local fleet had the lowest success. Most skippers reported an annual loss of fewer than 25 net panels per boat/year, and the effective mean number of panels lost per boat/year was estimated as 3.2, 5.1 and 7.4 for the local fleet, coastal fleet and hake metiers, respectively.

Clam-dredging results in the exposure of Spisula solida individuals not caught by the dredge. Subsequent survival depends on clam damage, reburial time, and the time needed by predators to reach the impacted area.We analyse these variables and discuss the importance of predation on exposed S. solida caused by dredge fishing. Sampling was performed in July 2000 off the southern coast of Portugal, at Vilamoura, a traditional S. solida sandy fishing ground.We compared the time needed for S. solida individuals to rebury themselves, relative to the abundance of potential predators. Bivalves collected by divers were placed on the seabed, and the times required for reburial were measured. These were compared with the times needed for reburial of the clams exposed by dredge impact. At each of three dredge tracks, we analysed the number of predators that entered three equal quadrats (0.0250 m2) per minute. These results were compared with a non-affected control area. Impact caused by the fishing dredge significantly increases the number of exposed S. solida clams ðp < 0:05Þ and the abundance of potential predatory species ðp < 0:05Þ. The brittle star Ophiura texturata was the most abundant and first species to reach the dredge track (less than 3 min after dredge impact). Other species reaching the dredge track were Pomatochistus spp. (6 min after impact), Diogenes pugilator, and Nassarius reticulatus (both 9 min after impact). Although predators reached the impacted area while S. solida bivalves were still exposed, our results suggest that predation on the non-buried clams in the dredge track is not a major factor for subsequent indirect mortality of S. solida.

This study reports weight–length relationships for 50 selected fish species of the Algarve coast (southern Portugal). Specimens were caught during fishing surveys with different types of fishing gears (trawls, nets, long-lines and traps) or sampled during whole fish market sampling operations. A total of 22 825 individuals were sampled, belonging to 50 fish species from 25 families. The best represented was family Sparidae (13 species), distantly followed by Scombridae and Triglidae (four species), Carangidae (three species), and by Gadidae, Haemulidae, Scyliorhinidae, Serranidae and Soleidae (two species). In numerical terms, the most important species were Trachinus draco and Diplodus bellottii , with 2767 and 2144 individuals, respectively, followed by Citharus linguatula (1844), D. vulgaris (1206), Microchirus azevia (1165), Scorpaena notata (1118) and Pagellus erythrynus (1075). To the author’s best knowledge, this study presents the first references on weight–length relationships for six fish species worldwide, for 15 species for the northeastern Atlantic, for 20 species for Portuguese waters and for 25 species for the Algarve coast (southern Portugal).

The shell growth and reproductive cycle of Donax trunculus (Mollusca: Bivalvia) from southern Portugal were studied from December 1993 to November 1994. Both the acetate peel method and quantification of surface growth rings were used to establish age and estimate growth rate. Widely spaced growth bands were formed in spring and summer whilst narrowly spaced bands were deposited in late summer and early autumn. No cessation of growth was observed during the winter. The von Bertalanffy growth curve estimated from the internal bands did not differ significantly from that obtained from the surface rings. However, the age of clams can be determined more accurately from acetate peels than directly from surface rings. Laboratory experiments demonstrated that periodicity of the deposition of microgrowth bands was related to an innate rhythm. Gonadal development was monitored using standard histological methods. Both males and females showed synchronism in gonadal development. The gametogenic cycle began in late November and ended in late August. Spawning occurred between March and August with two major spawning phases: March and May–August. D. trunculus reached maturity during the first year of life.