While fishing resources available to fishermen are becoming increasingly scarce, management actions that regulate these resources are becoming more restrictive, to such an extent that some fisheries remain closed for years. The anchovy fishery in the Bay of Biscay, which was closed for 5 years, from 2005 to 2009, is one of the most important sources of revenue for the Basque pelagic purse-seiner fleet. Throughout the course of this closure the fleet was forced to find alternative revenue streams. In the present study, the fishing alternatives were analysed before and during the anchovy fishery closure, defining an adaptability indicator to measure the ability of the fleet to cope with fisheries closures. Four differently-behaved segments were found within the purse-seiner fleet. Only one of these segments managed to maintain the same level of turnover during the anchovy closure, while the others could not reach a minimum level of adaptability. Compensation of the fishery closure through financial aid was studied, analysing the impact that public aid had on the profit of each segment and on the adaptability indicator.

Several fleets with various fishing strategies operate as a mixed fishery in the Bay of Biscay. Among the main fleets, bottom trawlers target Norway lobster (Nephrops norvegicus) and, together with gillnetters, they also catch hake (Merluccius merluccius). Trawling leads to average-size catches that are below the minimum landing size (MLS); such catches are discarded since they cannot be sold. These discards result in negative impacts on stock renewal, as most of them do not survive. This also results in an economic loss for both bottom trawlers and gillnetters since these discards represent a future loss of rent. This study, based on the 2009 and 2010 selectivity experiments at sea, assesses the short- and long-term bio-economic impacts of four experimental selective devices aimed at reducing N. norvegicus and M. merluccius discards over a 20-year simulation period. Tests were conducted at sea on a research trawler. Using the impact assessment model for fisheries management (IAM model), selectivity scenarios for trawlers in the Bay of Biscay were compared to a theoretical selective scenario of adopting an optimal device that catches only N. norvegicus and M. merluccius above MLS (9 cm and 27 cm total length, respectively). Costs and benefits were analyzed with the objective of finding the best compromise between a reduction in discards of undersized fish and a loss of valuable catches among the experimental devices. Selectivity scenarios show positive impacts on stocks but different economic impacts between fleets. The combination of a square mesh cylinder with a grid and square mesh panels gives the closest results to the theoretical scenario tested in terms of stock recovery and economic benefits. This experimental device leads to low economic losses in the short term and eventually to higher N. norvegicus yields, which would be favourable for fleets that greatly contribute to N. norvegicus fishing efforts.

In this study, we compared the size selectivity of a T90 codend (nettingturned by 90 degrees) with that of a standard codend made of similar netting. Sea trialswere conducted in a Norway lobster directed fishery in the Kattegat-Skagerrak area, wherethere is a need for improved selectivity because of a severe discard problem. The codendswere tested by fishing simultaneously with them in a twin trawl rig. Codend covers mountedwith Minisamplers were used, which made it possible to catch individuals escaping duringtowing and haul-back separately. Herein we proposed a model to assess the sequentialselection during towing and haul back. This model takes into account the parameterCtow, which can be interpreted as theproportion of fish that comes into contact with the codend meshes during towing and,thereby, has a chance of escape. Compared to the standard codend, the T90codend retained fewer Norway lobster both below and above the legal minimum landing size(40 mm, cephalothorax length), thereby causing a reduction of commercial catch. Thedifference was mainly due to a significantly higher escape rate during towing for theT90 codend. For plaice below minimum landing size (27 cm), theretention was slightly but significantly higher for the T90 codendcompared to the standard codend. A model developed for both codends showed that not allplaice are able to attempt escapement during the towing process. For cod, the resultsindicated an increased L50 (the length at which 50% of this species iscaught) for the T90 codend, but the effect was not statisticallysignificant, probably due to the limited number of cod retained during the sea trials. Theresults demonstrated that, for all three species, a significant proportion did escapeduring haul-back in both codends.

The survival of the highly endangered, anadromous fish species North Sea houting (Coregonus oxyrinchus) depends on the correct timing of downstream dispersal during its early ontogenetic stages. To date, however, no studies have investigated the ontogenetic differentiation of swimming performance and behaviour, including the potential of habitat complexity to influence dispersal rates. By testing larval and juvenile North Sea houting in a laboratory, we examined (1) swimming performance measured as maximum swimming performance (Umax) and routine swimming speed (Uroutine) and (2) the potential of habitat complexity (i.e., cover providing shade) to influence dispersal behaviour in an indoor stream channel. The Umax and the Uroutine were 9.4 and 4.6cm s-1, respectively, in the larvae [body length (BL) s-1: 7.3 and 3.5, respectively], and 25.2 and 16.3 cm s-1 in the juveniles (BL s-1: 7.0 and 5.2, respectively). We compared laboratory swimming performance data with water speeds in North Sea houting spawning areas in the Danish River Vidaa. Results showed that the water speeds present in 95% and 85% of the water column caused downstream displacement of larvae and juveniles, respectively. However, areas with slow-flowing water near river banks and river beds could function as nursery habitats. Stream channel experiments showed that cover providing shade caused delayed dispersal in both larvae and juveniles, but the larvae dispersed later and spent less time under cover than the juveniles, a finding that implies ontogenetic effects. Finally, the larvae refused to cross an upstream-positioned cover, a behaviour that was not observed in the juveniles. Therefore, habitat complexity may have the potential to influence dispersal behaviour in both larval and juvenile North Sea houting. Overall, we provided the first evidence of ontogenetic differentiation in the North Sea houting. These findings will be valuable for the development and dissemination of science-based conservation strategies.

Among other applications, self-feeding has been used to study food preferences in fish allowing them to choose between feeders with different food content. Preference tests assume that (i) trigger actuations are motivated by appetite, (ii) fish can learn which feeder contains which food and discriminate between feeders solely on the basis of their content, and (iii) in groups of fish, the triggering preferences is representative for the individuals of the group. We studied individual triggering behaviour in four groups of 14 Atlantic cod (length of 34  ±  2 cm, weight of 424  ±  102 g, mean  ±  SE, water temperature comprised between 7–8 °C) that were first given the choice between two self-feeders with identical content (Period 1 of 14 days) and subsequently with one feeder full and the other empty (Period 2 of 14 days) . In all four groups, one or two individuals performed the majority of the actuations, and in three groups the high triggering fish was a female high-ranked for size and growth rate. Cod displayed a preference for one of the two feeders despite their identical content. When the preferred feeder was emptied, the preference switched after one to eight days but both feeders were still actuated throughout the experiment. In conclusion, the assumption that actuation frequency reflects food preference and is representative for the individuals of the group may not be true, at least for Atlantic cod. If aiming at determining preferences representative for the whole population multiple representative fish should be kept isolated in separate tanks, with self-feeders containing each food option, on each tank.

The capacity to bioaccumulate trace metals present in San Jorge Bay, Antofagasta, Chile,was determined in northern scallop, Argopecten purpuratus, to examine thevalue of this important commercially species as a bioindicator of heavy metal pollution inareas where it is cultured. Scallops were sampled in summer 2009 in four sites: threenatural populations (Coloso, Historic District and La Rinconada, marine reserve), and acommercial hatchery (Colorado). The concentrations of three heavy metals (copper, cadmiumand lead) were then determined through stripping chronopotentiometric methods, and thelevels of four biomarkers: three genes implicated in the stress and oxidative metabolism,i.e., glutathione peroxidase (GPx), glutathione s-transferase (GST) and heat shock protein70 (HSP70), and a protein marker in the digestive gland and gill, a metallothionein (MT).The Historic District, located in the downtown area of the city, showed the highest metalconcentration of all the sampled sites, as well as the highest levels of the fourbiomarkers. This can be largely attributed to the nearby international port area of thetown and high sea traffic flow, exacerbated by the prevailing winds.

Producing high quality cultured black pearls from Pinctada margaritifera is one of the major challenges for the “pearl oyster” industry in French Polynesia. In order to assess donor effect on cultured pearl quality, wild Pinctada margaritifera originating from the Tuamotu Archipelago were used in a duplicated grafting experiment. After 12 months of culture, nucleus retention was assessed and seven pearl quality traits recorded on the 454 cultured pearls harvested from the experiment. The traits scored were nacre thickness and pearl weight, surface defects, lustre, grade, and the colour components: 1) darkness of cultured pearl colour, and 2) visual perception of colour class (bodycolor and/or overtone). Our results demonstrate for the first time that individual wild donors of implanted mantle grafts significantly affect these seven quality traits in P. margaritifera cultured pearls. This finding was repeated in two series of grafts made by different professional grafters. The wild donors could be ranked from “best” (e.g., the donor whose grafts produced the cultured pearl with the maximum lustre) to the “worst”. Moreover, we showed strong correlations between: 1) cultured pearl nacre thickness and grade, with grade A showing the greatest nacre thickness on average compared with grade D and rejects; and 2) nacre thickness/cultured pearl weight and colour components (darkness and visual “colour categories”), with the palest cultured pearls (i.e. white cultured pearls) being the smallest (lowest nacre thickness and weight). Thus, one way of enhancing P. margaritifera foundation stocks for a selective breeding program could be to select the “best” donors, using appropriate molecular tools. Generation of selected donor lines from these stocks through hatchery production would be one way to increase the quality of cultured pearl farming of P. margaritifera in French Polynesia.