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The tooth histology of a total 22 and 95 short-beaked common dolphins ( Delphinus delphis) from Scottish ( UK) and Galician ( Spain) waters, respectively, was examined to determine whether the incidence of mineralization anomalies could be related to certain stressful conditions linked with life-history events or to exposure to anthropogenic pollutants (i.e. Polychlorinated biphenyls and Dichlorodiphenyltrichloroethanes). Overall, the incidence of five categories of mineralization anomalies increased with age. Model results indicated that the presence of cemental disturbance increased with age, body length and sexual maturity in common dolphin from both areas. In addition, incidence of dentinal resorption and accessory lines increased with age and body length in Galician animals. The time course of appearance of dentinal resorption and cemental disturbance was similar to the time course of maturation suggesting a link between anomaly occurrence and the age at which the animals become sexually mature. There were two age ranges at which marker lines tended to appear: 1-2 and 6-8 years old, which coincided with the beginning of weaning and/or the age at sexual maturation, respectively, suggesting an association with these two major life-history events. Pulp stones were recorded in teeth of a few mature Galician dolphins ( n = 4). No evidence was found that the presence of mineralization anomalies in dolphin teeth was significantly related to persistent organic pollutant concentrations in the blubber. Our results provide evidence that certain tooth mineralization anomalies could be interpreted as time markers associated with life-history events, potentially representing a powerful tool for long-term monitoring and modelling. [ABSTRACT FROM AUTHOR]

Seasonal and size-related patterns in feeding habits of the Atlantic bonito ( Sarda sarda) in the Northeast Aegean were investigated over a 2-year period May 2007 - May 2009 based on analysis of stomach contents of 134 fish ranging from 266-655 mm fork length. The fish were caught by purse-seine boats operating around the islands of Lesvos and Chios ( Greece). Of the stomachs examined, 46% contained at least one prey item and significant seasonal and size-related patterns were found in the occurrence of non-empty stomachs. The overall diet composition in terms of numerical importance was 71% fish, 28% crustaceans and 1% cephalopods. Of the fish, Engraulidae ( Engraulis encrasicolus) were the dominant prey taxon, followed by Centracanthidae ( Spicara spp.) and then Clupeidae ( Sardina pilchardus). Statistically significant monthly variation in diet was apparent, suggesting that S. sarda take advantage of seasonally abundant prey fish in the study area, but no size-related variation in the importance of the main prey species was detected. [ABSTRACT FROM AUTHOR]

This study demonstrates the utility of trawl data, collected during acoustic surveys of pelagic fish stocks as a way of confirming fish identification, to characterize the pelagic community, as well as allowing description and prediction of fish distribution patterns, based on data from Spanish Atlantic Ocean shelf surveys during spring 2005-2011. The composition of the pelagic community is described, as well as spatial and temporal patterns of variation in both the community composition and the presence and importance of two of the main exploited pelagic species, sardine Sardina pilchardus and anchovy Engraulis encrasicolus. The most important species in terms of both frequency of occurrence and standardized mass in hauls were mackerel Scomber scombrus, hake Merluccius merluccius, horse mackerel Trachurus trachurus, S. pilchardus and bogue Boops boops. Multivariate analysis indicated significant effects of depth, geographical area and year on haul composition. Descriptive generalized additive models ( GAM), with latitude, longitude and depth as predictors, identified clear spatial patterns in the occurrence and abundance of both S. pilchardus and E. encrasicolus, with abundance being highest closer to the coast and, in the case of E. encrasicolus, higher near the French and Portuguese borders. Further GAM analysis, using environmental variables to explain spatial patterns, revealed significant effects of depth and sea surface temperature ( SST) gradient and depth on S. pilchardus importance, while E. encrasicolus importance was related to SST. The importance of both species in hauls was higher in the years of higher spawning stock biomass ( SSB) and E. encrasicolus also appeared to expand its range when SSB was higher. [ABSTRACT FROM AUTHOR]

The behavioural effects of confinement of sardine Sardina pilchardus in a purse seine were evaluated through three laboratory experiments simulating the final stages of purse seining; the process of slipping (deliberately allowing fishes to escape) and subsequent exposure to potential predators. Effects of holding time (the time S. pilchardus were held or entangled in the simulation apparatus) and S. pilchardus density were investigated. Experiment 1 compared the effect of a mild fishing stressor (20 min in the net and low S. pilchardus density) with a control (fishing not simulated) while the second and third experiments compared the mild stressor with a severe stressor (40 min in the net and high S. pilchardus density). In all cases, sea bass Dicentrarchus labrax were used as potential predators. Results indicated a significant effect of crowding time and density on the survival and behaviour of slipped S. pilchardus. After simulated fishing, S. pilchardus showed significant behavioural changes including lower swimming speed, closer approaches to predators and higher nearest-neighbour distances (wider school area) than controls, regardless of stressor severity. These results suggest that, in addition to the delayed and unobserved mortality caused by factors related to fishing operations, slipped pelagic fishes can suffer behavioural impairments that may increase vulnerability to predation. Possible sub-lethal effects of behavioural impairment on fitness are discussed, with suggestions on how stock assessment might be modified to account for both unobserved mortality and sub-lethal effects, and possible approaches to provide better estimates of unobserved mortality in the field are provided. [ABSTRACT FROM AUTHOR]

The skinnycheek lantern fish Benthosema pterotum (Myctophidae) represents a virgin resource in the Oman Sea. Because of its potential importance for fishmeal production there has been great interest during the last decade in starting commercial exploitation. Acoustic surveys to estimate stock biomass and trial fishing using pelagic trawls were carried out in Iranian waters of the Oman Sea from 1992 to 1998. Lantern fish schools are found in offshore waters, on the edge of the continental shelf wherever sea depth is more than 100 m. During the day the fish occur in two vertical layers, with the densest schools in the shallower layer (80–130 m), whereas at night B. pterotum occur in a single dispersed layer closer to the surface (mainly at 30–70 m). Biomass estimates range from 1 to 4 million tonnes (t), with an average of 2.3 million t. Densities vary seasonally, with the highest densities recorded in spring (May–June) and lowest in autumn (October–November). The highest densities were seen in the western Oman Sea. Although recommendations can be made with regard to the best fishing seasons, areas and depths, trial catch rates were too low (<30 t daily per boat) to support a commercially viable fishery. Further trials are needed to identify the best gear and vessel size. [ABSTRACT FROM AUTHOR]

Little is known about the feeding ecology of pygmy sperm whales ( Kogia breviceps) in the Northeast Atlantic. Results are presented on the stomach contents of five whales stranded on the Galician coast (NW Spain) between 1995 and 2002 and seven whales stranded on the French Atlantic coast between 1984 and 2001. These results are compared with those obtained from the stomach contents of two pygmy sperm whales (a pregnant female and her calf ) stranded on the Scottish (UK) coast in 1999, the first records of the species in Scotland. In 13 out of 14 cases, food remains consisted almost entirely of cephalopod beaks, although some crustacean and fish remains were also present. In all the Spanish specimens, the identified prey were oceanic species: the cephalopods Histioteuthis reversa, H. bonnellii, Todarodes sagittatus, the viperfish Chauliodus sloani, and the giant mysid Gnatophausia sp. The same cephalopod species were found in the stomachs of the whales stranded in Scotland, although both whales had also consumed neritic cephalopod species such as Rossia macrosoma and other sepiolids. In the French specimens, almost all prey identified were oceanic cephalopods ( H. reversa, Brachioteuthis riseii, T. sagittatus, Taonius pavo, etc.), but remains of crustaceans and a neritic squid ( Loligo forbesi) were also found. One whale from France had eaten mainly Henslow's swimming crab ( Polybius henslowi). Results from the present study are consistent with those found by other authors in the Azores and the Canary Islands in that pygmy sperm whales appear to be mainly teuthophagous, with histioteuthid squids forming an important part of the diet. Strandings records suggest that occurrence of pygmy sperm whales in the NE Atlantic may be seasonal, with most strandings occurring in autumn and winter. [ABSTRACT FROM AUTHOR]

Detailed observations of the behaviour of harbour seals, Phoca vitulina L., at sites within the estuaries of the Rivers Dee and Don, in north-eastern Scotland, were made over two full years between 1993 and 1996. Small numbers of grey seals, Halichoerus grypus Fab., were also present. The presence of seals within the estuaries was strongly related to season, with maximum numbers observed in winter and early spring; seals were virtually absent in June and July. The River Don was used largely as a haul-out site, while the River Dee was used predominantly as a foraging site, although it was not possible to determine whether the same seals were using the two estuaries. More seals were hauled-out on the River Don during twilight and dark than in daylight. The seals were observed to eat mostly salmonids, Salmo salar L. and S. trutta L., unidentified roundfish and flounder, Pleuronectes flesus L. The otoliths identified in scats collected at the mouth of the River Don belonged to marine species indicating that the seals were also feeding outside the estuaries. A minimum estimate is given of the numbers of large salmonids eaten in each river during the course of the year. Although no information was available on the numbers of salmonids using the rivers or the reproductive status of the fish eaten by the seals, as a cause of mortality, seal predation on large salmonids in estuaries is apparently an order of magnitude less important than mortality caused by angling within the river. [ABSTRACT FROM AUTHOR]

In this study, we consider the influence of mesoscale oceanographic processes around the Falkland Islands (Islas Malvinas) in the South-west Atlantic, during the period in which the commercial squid fishery for Illex argentinus operates. Spatially referenced fishery data and satellite-derived advanced very high resolution radiometry (AVHRR) sea surface temperature (SST) data were examined using geographic information system (GIS) techniques. The distribution and relative abundance of I. argentinus in the Falkland Islands fishery was examined for the period 1989–96. Three consistent areas of high abundance were observed to the north-east (shelf-break region) and north-west (shelf region) of the islands, and close to the northern coast of East Falkland. Areas of high sea surface temperature gradients (thermal gradients) extracted from remotely sensed satellite images were used as an indicator of mesoscale oceanographic activity and compared with the location of the fishery. I. argentinus were found to be associated with areas of thermal gradients, commonly seen at the interface of Falkland Current and Patagonian shelf waters. The techniques used in this analysis allow the overlay and analysis of physical oceanographic and fishery data with potential applications in fisheries management and operational fisheries oceanography. [ABSTRACT FROM AUTHOR]

This study demonstrates the utility of trawl data, collected during acoustic surveys of pelagic fish stocks as a way of confirming fish identification, to characterize the pelagic community, as well as allowing description and prediction of fish distribution patterns, based on data from Spanish Atlantic Ocean shelf surveys during spring 2005-2011. The composition of the pelagic community is described, as well as spatial and temporal patterns of variation in both the community composition and the presence and importance of two of the main exploited pelagic species, sardine Sardina pilchardus and anchovy Engraulis encrasicolus. The most important species in terms of both frequency of occurrence and standardized mass in hauls were mackerel Scomber scombrus, hake Merluccius merluccius, horse mackerel Trachurus trachurus, S. pilchardus and bogue Boops boops. Multivariate analysis indicated significant effects of depth, geographical area and year on haul composition. Descriptive generalized additive models ( GAM), with latitude, longitude and depth as predictors, identified clear spatial patterns in the occurrence and abundance of both S. pilchardus and E. encrasicolus, with abundance being highest closer to the coast and, in the case of E. encrasicolus, higher near the French and Portuguese borders. Further GAM analysis, using environmental variables to explain spatial patterns, revealed significant effects of depth and sea surface temperature ( SST) gradient and depth on S. pilchardus importance, while E. encrasicolus importance was related to SST. The importance of both species in hauls was higher in the years of higher spawning stock biomass ( SSB) and E. encrasicolus also appeared to expand its range when SSB was higher. [ABSTRACT FROM AUTHOR]