The loliginid squid Loligo forbesi has a flexible life-cycle, involving variable size and age at maturity, presence of summer and winter breeding populations, and extended periods of breeding and recruitment. This paper reviews life history data collected since 1983 from the commercial fishery in Scottish (UK) waters, alongside fishery data collected since 1970, and examines (a) the relationship between body size and timing of maturation, (b) evidence for shifts in the relative abundance of the summer and winter breeding populations, and (c) the possible role of environmental signals in determining the timing of breeding. Evidence from fishery data suggests that, since the 1970s, the summer breeding population has declined while the winter breeding population now dominates and breeds later than was previously the case. Length-weight relationships and size at maturity showed significant inter-annual and seasonal variation during the period 1983-2001. Males are shown to decline in relative weight as they mature while females increase in relative weight; possible interpretations are discussed. High autumn/winter temperatures (high winter NAO values) were associated with high squid abundance and precocious maturation and tended to favour high abundance in the following year, along with increased body weight at length and a decrease in the proportion of animals breeding in December. High abundance in summer, conversely, leads to a fall of body weight at length in the following year. Thus there may be alternation of precocious and slow maturation, and/or summer and winter breeding, driven by a combination of environmental conditions and intraspecific competition.

The terms ‘ecosystem-based fisheries management’, ‘ecosystem-based management’ and ‘ecosystem approach to fisheries’ have recently entered the vernacular of fisheries management. Examination of contemporary guidelines and proposals for such an approach illustrates that ecosystem-based fisheries management is, for all intents and purposes, a re-expression of the objectives and processes associated with ecologically sustainable development (and associated international instruments). Since the early 1990's, all levels of government in Australia have committed themselves to the concept of ecologically sustainable development, and a complex network of policies and laws exist to support this, particularly in natural resource management. One significant outcome of these instruments is the application of environmental impact assessment to the management of fisheries. This has forced extensive deliberation of the ecological impact of fisheries and stimulated the development and application of new research tools. Application of environmental impact assessment to the management of fisheries has been a crucial step for the implementation of ecosystem-based fisheries management in Australia. These assessments are embedded within a range of legal and policy instruments that capture the ecological, economic and social dimensions of fisheries. The scientific challenges associated with many aspects of ecosystem-based fisheries management are very significant, but it is likely that the value-based nature of the underlying environmental issues will continue to dominate the managerial agenda.

The recruitment of Strangomera bentincki (common sardine) and Engraulis ringens (anchovy) and the relationships with oceanographic conditions in the upwelling ecosystem of central-south Chile were investigated from 1990 to 1998, with emphasis on the 1997–1998 El Niño. Time series of recruitment, biomass, local sea surface temperature, and a coastal upwelling index were used to explore relationships during the spawning (July–August) and pre-recruitment (August–December) periods. The 1997–1998 El Niño caused physical changes in the small pelagic fish habitat off central-south Chile. Anomalous sea surface temperatures (SST) and upwelling indexes began to be detected from May 1997 and persisted into 1998. Recruitment of common sardine showed significantly negative relationship with SST anomalies during the pre-recruitment period, as well as with the upwelling index during the peak of spawning. However, the recruitment of anchovy did not seem to be affected by the environmental changes observed in the 1990s. Instead, the recruitment rate of anchovy showed negative relationship with the recruitment rate of common sardine. We conclude that the conditions of the 1997–1998 El Niño off central-south Chile affected the survival of common sardine offspring, and that the recruitment success of anchovy could be determined by less-abundant cohorts of common sardine through a biological mechanism of interaction.

When assessing oyster-reef habitat in estuaries it is important to understand the influence of salinity on the spatial and temporal variability of associated organisms. How comparable is community structure among stations located at different points along the salinity gradients of estuaries or among tidal tributaries that experience different levels of freshwater inflow? Do assemblages vary seasonally in response to changing salinity and freshwater inflow? To address these questions, multivariate techniques were employed to analyze decapod crustacean and fish abundance data. Organisms were collected at three reefs along the salinity gradient of three estuaries: the Caloosahatchee River and estuary, Estero River and Bay, and Faka Union Canal and Bay. Additional collections were made from reefs located near the mouths of Estero Bay's five tidal tributaries. Samples were dominated by the decapods Eurypanopeus depressus and Petrolisthes armatus. Commonly occurring species included the decapods Panopeus obesus, Alpheus heterochaelis and Rhithropanopeus harrisii and the fishes Gobiosoma robustum, Lophogobius cyprinoides and Gobiesox strumosus. Analysis of similarities suggested differences among stations located along the salinity gradients of all three estuaries. Community structure also varied among stations located near the mouths of the tidal tributaries of Estero Bay. Multidimensional scaling identified community structure present at upper stations as distinct from that downstream and at high-flow tributaries as distinct from that near low-flow tributaries. Upper stations and stations near high-flow tributaries were typified by E. depressus and gobiid fishes. Downstream stations and stations near low-flow tributaries were typified by E. depressus and P. armatus. Percent dissimilarity was greatest when upper and lower stations were compared along the salinity gradient or when low salinity and high-salinity sites were compared among tributaries. Within-station sample variability tended to be higher upstream or in association with high-flow tributaries.

Most recent authors have called the Chilean blue mussel (formerly Mytilus chilensis) Mytilus edulis. Mussels from four nominal species (Mytilus edulis, M. trossulus, M. galloprovincialis and M. chilensis) were collected from the eastern coast of Newfoundland, Canada, New Zealand and the southern coast of Chile. Canonical discriminant analysis of selected shell morphometrical characters showed that although there is some overlap in canonical variates, the three nominal species, M. edulis, M. trossulus and M. chilensis can be morphologically divided into three distinct groups. The two nuclear-DNA markers (ITS and Glu-5) and the mtDNA marker studied indicate that the nuclear and mitochondrial genomes of M. edulis and M. trossulus are different. M. edulis, M. galloprovincialis and M. chilensis share similar restriction fragment patterns for the mtDNA and for the ITS nuclear-DNA marker, while the Glu-5 polymerase chain reaction (PCR) assay showed that the M. edulis and M. chilensis genotypes disagree, producing species-specific banding patterns that can be used as a diagnostic marker between the two nominal species. The molecular and morphometric data reported here give more evidence to support the view of other authors that the Chilean blue mussel should be included as M. edulis subspecies: Mytilus edulis chilensis.

With the aim of establishing cryopreservation protocols for oyster (Crassostrea gigas) embryos, toxicity of single or combined cryoprotectants to oyster embryos was investigated. In experiments on the toxicity tolerance of oyster embryos, four conventional cryoprotectants, namely, acetamide (A), dimethyl sulfoxide (DMSO), ethylene glycol (EG) and propylene glycol (PG), with concentrations from 1 to 5 M were used to test the toxicity tolerance of oyster embryos at eight different developemental stages. On a molar-equivalent basis, DMSO appeared to be less toxic to PG, EG and acetamide in general. Oyster embryos were tolerant to low concentrations of all cryoprotectants tested in the range from 1 M to 2 M for all developmental stages. Early stage embryos were more vulnerable to high concentration (4 M and 5 M) cryoprotectants tested than late stage embryos. Experiments were subsequently performed to study the combined effects of DMSO and acetamide adding trehalose or glucose in reducing toxicity to 4 hour oyster embryos. The use of trehalose or glucose reduced toxicity of high cryoprotectant concentrations. Survival was higher when DMSO was combined with acetamide than when using DMSO or acetamide alone at high concentration (5 M). By adding trehalose to combined 5 M DMSO and acetamide (total concentration) an average survival rate of 67 ± 7% was obtained in contrast to 8 ± 5% or 2 ± 1% survival when testing with 5 M DMSO or 5 M acetamide, respectively.

Because preying on close relatives may cause a loss of inclusive fitness, cannibalistic animals are generally deemed to cannibalise non-related conspecifics preferentially to kins. Whether this basic principle also applies to fish exerting intracohort cannibalism at an early developmental stage is uncertain, and more intense cannibalism among mixed progenies might just be a consequence of greater size heterogeneity. To investigate this, progenies of sharptooth catfish of equivalent initial body weights but with contrasting size heterogeneity were reared separately or in mixed groups containing equal proportions of each progeny (27 ± 1°C, 12 h light:12 h night, 2.5 L aquaria, 100 or 200 fish·L–1). Cannibalism was monitored on a daily basis until the end of the larval stage (3–15 days after hatching). Cannibalism in mixed groups was intermediate between those in pure progenies, and was positively correlated (R2 = 0.803, P < 0.01) with initial size heterogeneity, irrespectively of fish origin. This finding does not exclude that catfish larvae were able to discriminate between siblings and non-related fish, but this obviously had very little influence on cannibalism. The implications of this finding are discussed, as they apply to prey selection in fast growing larvae, and aquaculture of catfish.

A method for acoustic abundance estimation by horizontal guided sonar of fish schooling close tosurface is presented. The basic principle is to measure the horizontal area of schools in situ, and derive the school biomass subsequently through a school area to school biomass relationship. The application of the method is exemplified through a sonar survey in the eastern North Sea-Skagerrak in September 1990. The areas of recorded schools were measured by the estimate function of a Furuno CSH-70 sonar, and selected schools were captured by purse seine to establish a school-area to school-biomass relationship. In the actual region, the biomass of herrig (Clupea harengus) and mackerel (Scomber scombrus) was estimated to about 90 000 and 43 0000 tons, respectively. The accuracy of the method is discussed and improvements are suggested.

Retention of the second polar body for the production of triploid Arctic charr (Salvelinus alpinus) was induced by 65 MPa (650 bar) pressure shocks applied 30, 40 or 50 min after fertilization, each shock lasting 5 min. Triploid yield (percentage of relative survival to control × percent triploidy) varied from 55 to 100 % and it was generally superior to 80. Despite increased mortality and decreased growth in diploid charrs during the spawning period, growth and survival did not differ between diploid and triploid Arctic charr up to and during their third year of life. Most of the triploid males had developed testis, but they did not render milt; few triploid females had developed ovaries. Fecundity of triploid females was low and fertilized eggs from triploid females did not hatch.

European hake Merluccius merluccius is the main commercial demersal species in the Gulf of Lions (Northwestern mediterranean). This fish is exploited by French and Spanish trawler fleets and by small-scale fisheries using gillnets and longlines. Data on landings and the demography of catches by type of gear are now available for the period 1988–1991. The assessment of the hake stock was carried out using methods of virtual population analysis (VPA), or cohort analysis, based respectively on mean pseudocohorts and cohorts by age. The results of these VPA were then analysed and compared from a methodological point of view. The general results have confirmed previous studies with regard to the level of exploitation of the species. The two methods gave quite similar results for fishing mortality rates and for mean biomass. The maximal fishing mortality rate was observed at age 4, but it was already high at age 1, due to the exploitation of juveniles by trawlers. The mean biomass was about 7 000 tons. The high values for turnover (about 80% or more) and for the maximal biomass/mean biomass ratio (23% or more) indicated a high level of exploitation but did not seem high enough to be dangerous for the stock. Yield-per-recruit analysisshowed also that the present level of exploitation is far above the optimal sustainable level.

Escapement through the body or under the footrope of the sampling trawl used for the Mediterranean international trawl survey programme (MEDITS) was assessed i) by means of visual observations performed with a towed operating vehicle equipped with a high-sensitivity video camera, and ii) by attaching small bags to the outside of the trawl body and under the footrope. Due to the small size of most of the individuals present in the study area and to the towing speed, fish behaviour in front of the trawl could not be frequently observed. In contrast, their behaviour was easily observed inside the net, especially upstream and inside the codend. Some species, such as horse mackerel (Trachurus sp.), showed greater swimming endurance compared with others such as annular seabream (Diplodus annularis). In three fishing trips conducted in different seasons in 1996 and 1997 to obtain data on several species in different areas of the Adriatic, six small net bags were mounted outside the body of the MEDITS trawl to quantify escapement through the trawl belly and under the footrope. Significant escapement of many species occurred in the near-bottom part of the side panels. Norway lobster (Nephrops norvegicus) had the highest rate (64 %), mainly represented by small-size individuals. The escapement of greater forkbeard (Phycis blennoides) was also high (53 %). For hake (Merluccius merluccius), common pandora (Pagellus erythrinus) and poor cod (Trisopterus minutus capelanus), rates ranged from 10 to 16 %. The escapement of red mullet (Mullus barbatus) was very low despite their great abundance. Blue whiting (Micromesistius poutassou) escaped mainly through the mid-height part of the side panel. This great variability of escapement values could affect the proportion rates of the species sampled during a standard survey. Different escape behaviours among size classes were observed for M. poutassou, T. minutus capelanus and P. erythrinus, with smaller individuals tending to escape towards the bottom and larger ones towards the higher parts of the trawl body. In the species where the escape rate was size-dependent, therefore, the size-frequency distributions obtained from the codend catch may not reflect actual size-frequency distributions.

This work presents a method to observe pelagic fish around drifting fish aggregating devices (DFADs). A triple-frequency vertical echosounder was employed to observe fish distributions in the vicinity of DFADs. Surveys were conducted in a star pattern that was centred at the DFADs. The objective of the study was to define a methodology for future acoustic studies. This goal was pursued by (i) studying the spatial distribution of fish aggregations, (ii) developing concepts for the grouping of observed aggregations and (iii) developing specifications for future autonomous acoustic tools. For this purpose 5 cruises were carried out in the western Indian Ocean. The multi-frequency approach proved useful as a means of separating acoustic detections into sound-scattering layers (e.g. plankton and micronekton), fish aggregations and individual fish. Fish target strength (TS) was measured. Four types of aggregations were found near DFADs: (i) dense structure (ii) medium structure (iii) loose structure and (iv) structure consisting of separated targets. More than 90% of these structures were found within a radius of 400 m and about 75% within 200 m of the DFADs. The spatial configuration of DFAD fish aggregations appeared to be more dynamic compared to aggregations near moored FADs. The spatial distribution and structure of DFAD aggregations have direct implications for their catchability by tuna purse-seiner. We have carried out the first quantitative acoustic recordings around DFADs, and obtained a better understanding of the spatiotemporal dynamics of fish aggregations around DFADs in the Indian Ocean. Based on this knowledge we are now working on specifications for instrumented buoys that are intended as autonomous data recording observatories for such pelagic environments.

The Pacific herring Clupea pallasi population in Prince William Sound (PWS), Alaska, is both a valuable commercial resource and an important forage species for marine fish and wildlife. Historically, the herring were managed by a combination of age-structured models and egg deposition estimates. When these methods predicted a large return for spring 1993 that failed to materialize, we began surveying with echointegration–purse seine methods. After a decade of acoustic surveys, we show the new approach yields highly precise biomass estimates, which are consistent with historical measures of the miles of beach spawning. When compared, we show the traditional methods overestimated stock biomass, which resulted in harvest rates approaching 40%. In contrast, the acoustic methods are most likely to underestimate biomass. Since the acoustic estimates can be quickly obtained, we recommend their use to set harvest quotas for the fishery in the spring just prior to harvest. The shift from the traditional preseason to inseason management practices for herring in PWS is consistent with the Precautionary Principle by the fact that protection of the spawning population does not rely on the ability of science to predict how the population is changing. Furthermore, synoptic infrared measurements on our night-time acoustic surveys revealed herring to be the most important winter forage to marine birds and wildlife in PWS, including the endangered Steller sea lion Eumetopias jubatus. Given the importance of forage to marine birds and wildlife in the North Pacific during the extended winter conditions (October–March), the implementation of inseason management for herring using echointegration–purse seine techniques may be the most effective method to restore depressed populations of marine birds and mammals in the North Pacific.

The long term influence of individual biological rhythms on group feed demand behaviour was investigated in European sea bass (Dicentrarchus labrax) held under controlled environmental conditions with an on-demand feeding system. The experiment was realized over 219 days with 190 fish distributed on 4 tanks. Sea bass had a mean body mass comprised between 139 g to 183 g. The number of feed demand acts by each individual was calculated daily, and the population could thus be partitioned into three categories (high-, low- and zero-triggering fish). The duration of the period that an individual held high-triggering status could vary, but was 63 ± 16 days on average. The transition period between two highest-triggering fish in one tank was on average 4 ± 4 days. The group feeding rhythm followed the same pattern of feed demand rhythm as the highest-triggering individual fish. When the highest-triggering fish was nocturnal, the totality of feed demand in the group was realized during the night with one peak at 22:00, corresponding to dusk under experimental conditions. When the highest-triggering fish was diurnal, the majority of feed demand in the group was realized during the light period with one peak at 06:00, corresponding to dawn, and/or another at 12:00. This study therefore highlights that sea bass group feeding behaviour is not the sum of individual feed demand behaviours, but is directed by the rhythm and behaviour of a few high-triggering fish. The regular changes of high-triggering fish in the group proved that it was not the identity of these particular fish that was most important for the group, but their role as a feed demand leader.

A total of 361 skipjack tuna (Katsuwonus pelamis) between 41.5 and 71.5 cm fork length and 333 yellowfin tuna (Thunnus albacares) between 48 and 150 cm fork length were collected in the western Indian ocean, between latitude 5° N to 10° S and longitude 45° to 65° E from February 1989 to November 1990. Yellowfin populations have one major reproductive season during the north monsoon while in skipjack the reproduction is almost continuous all year round with two peaks in activity during north and south monsoons. The gonadosomatic indexes (GSI) are correlated with the three climatic situations: the north monsoon, the south monsoon and two inter-monsoon seasons. The steroid hormone variations (oestradiol, oestrone and testosterone) are well correlated with the GSI in females. In males, maximum levels coincided with the two main reproduction periods in skipjack while the maximum values of testosterone and 11-ketotestosterone levels were only found during the north monsoon. Even if both species are continuous spawners, these results indicate the existence of different reproductive traits, especially when considering steroidogenesis and vitellogenesis. These findings suggest that over our fishing zone, the reproductive activity is significantly modulated by climatic changes.

Short-term storage over several days as well as cryopreservation of turbot (Scophthalmus maximus) sperm were studied. Two extenders, Ringer 200 and artificial seminal liquid (ASL2), are suggested for semen collection in order to avoid the deleterious effect of urine contamination, and for the purpose of short-term storage between 0 and 15 °C. Oxygen atmosphere is not suitable for turbot sperm storage. Turbot spermatozoa undergo cryopreservation with a high rate of success especially in a sucrose solution with 10% dimethyl sulfoxide (DMSO) and 10% egg yolk.

This review presents environmental and biological indicators of the impact of three major categories of inputs in coral reef lagoons i.e. particles, nutrients and metals. Information was synthesized to extract well established indicators together with some interesting new concepts currently under development, and to provide the reader with an assessment of their respective advantages and drawbacks. The paper has been organized according to the capacity of three categories of indicators to respond either in a specific or a non specific way to a given source of input. The first section focuses on abiotic indicators which main interest is to respond instantaneously and in a truly specific way to a given source of input. The second and third sections present informations on bioindicators either at the sub-individual level or at the individual to community level, indicator specificity generally decreasing as a direct function of biological or ecological complexity. This review showed that even though significant work has already been done on coral reef ecosystems, much more scientific studies are still needed to answer the growing local demands for simple and truly validated tools to be used in environmental surveys. It is further stressed that, due to the biological and environmental diversity of coral reef lagoons, a preliminary step of on-site validation must be considered as an absolute prerequisite when indicators are planned to be used in the frame of a local environmental monitoring programme.

In this paper, we present an approach to compare the impact of different management options on the dynamics of a mixed fishery. We used ISIS-Fish, a simulation tool aimed at evaluating the impact of spatial and seasonal management measures on the dynamics of mixed fisheries. The French Nephrops norvegicus (Norway lobster) – Merluccius merluccius (hake) mixed fishery of the Bay of Biscay was chosen as a study case. First, we parameterised the population and exploitation models. We then selected several management measures, including marine protected areas (MPAs) and total allowable catches (TAC), and parameterised fishermen's reaction to each measure. Then, a sensitivity analysis was performed according to a fractional factorial experimental design. Management scenarios were assessed and compared using a statistical simulation design. The sensitivity analysis showed the large influence of some parameters, such as natural mortality, N. norvegicus fecundity, and catchability on both abundance and catches. Given model parameters, an improvement of trawl selectivity and several MPA designs (differing in size, seasonality and location) were found to result in a significant increase in abundance over 10 years, especially for N. norvegicus. This study illustrates the need for a pluri-specific approach to fisheries assessment and management.

To study the behavior of dolphinfish (Coryphaena hippurus) around drifting Fish Aggregating Devices (FADs), we tagged individuals with long-lived, coded sonic transmitters and attached automated sonic receivers to drifting FADs in two regions of the Western Indian Ocean. Among the three tagging methods used in this study (surgery, external hooks, underwater bait without capture), the latest resulted in residence times significantly shorter than the other ones, likely due to regurgitation. Dolphinfish tagged with the two other methods usually stayed several days associated to FADs (Kaplan-Meier survival analysis 5.09 days, mean 6.25 days, SD 4.39 days, maximum 15.26 days), drifting with them. There was no significant difference in the residence times of dolphinfish in equatorial and tropical areas. While associated to FADs, dolphinfish spent most of their time close to floating object (<365 m). The total time spent away from FADs was low (median 8%), and likely corresponded to making feeding excursions. Dolphinfish did not form a single school while associated to a given FADs, but formed multiple small schools. FADs are likely to be sites with exchanges of individuals between schools. These results are discussed in regards to the possibility of FADs acting as ecological traps and the validity of meeting-point hypotheses as an explanation for fish aggregations under floating objects.

The pole and line tuna fishery in the Maldives relies heavily on an array of 45 anchored fish aggregating devices (FADs), making it one of the largest anchored FAD-based tuna fisheries in the world. We examined the behaviour of skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares) tuna around anchored FADs (1 000 to 2 000 m deep) in the Maldives using passive acoustic telemetry. Eight neighbouring FADs (distance range: 30 to 95 km, average: 50 km) were equipped with automated acoustic receivers in January 2009, for a period of 13 months. A total of 40 skipjack (37−54 cm FL) and 21 yellowfin (35−53 cm FL) tuna were tagged with Vemco V13 transmitters in January (start of the northeast monsoon, dry season) and November (end of the southwest monsoon, wet season) 2009 and released at the two central FADs within this instrumented array. No movement between FADs was observed for any acoustically-tagged tuna in the instrumented FAD array. These results suggest that FADs in the Maldives may act independently. The maximum time a tagged skipjack remained associated with a FAD was 12.8 days in January but only one day in November. In addition, residence times at FADs were found to differ with time (month) and space (FAD location) for skipjack tuna, suggesting that external biotic factors (e.g., prey, conspecifics or predators) might influence the time this species spends at FADs. In November, the residence times of yellowfin tuna (maximum observed time: 2.8 days) were three times greater than those of skipjack tuna at the same FADs. This specific difference could be explained either by the two species responding to different factors or by the species’ responses being dependent on the same factor but with different thresholds. No particular preference for time of departure from the FADs was observed. Some monospecific and multispecific pairs of acoustically-tagged individuals were observed leaving the FADs simultaneously. Thus, this study indicates a high degree of complexity in the behavioural processes driving FAD associations.