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Fish farms have been shown to aggregate large numbers of wild fish in their surroundings. Although little is known about how this affects the local fishery, two hypotheses have been put forward; a trapping and a protecting effect on wild fish. This study provides the first monitoring of commercial and recreational fishing activity at a fish farm. We assessed the effect on the small-scale fishery analysing the differences between fishing in farm proximity and away from the farm (in terms of catch rate, income and catch composition). Moreover, we estimated the biomass removal from fishing activities by farm employees inside the farm. The study was conducted from January 2011 to June 2012 at a Gilthead seabream farm in the NW Mediterranean. The findings revealed a relevant amount of commercial and recreational fishing effort in farm proximity. Yet, the results showed no benefit or difference of fishing in close proximity to the farm compared with areas away from the farm. Thus, we conclude that farm-aggregated fish are protected from the commercial fleet by the farm leasehold area, but remain vulnerable to hidden fishing practices inside the farm, where farm employees harvest more than 4 t of wild fish annually. [ABSTRACT FROM AUTHOR]

Factors influencing within-farm variability of wild fish aggregations have not been systematically studied. We tested the hypothesis that fish abundance and species composition vary between feeding and non-feeding periods and different bottom substrates within a Sparus aurata ( L.) farm. Sampling took place during feeding and non-feeding periods on six consecutive days in July 2011. Visual censuses were carried out at three different depths and at three sampling stations over rocky-sandy and sandy substrates respectively. In all, 33 species belonging to 17 families were observed. Total fish abundance, biomass and species community significantly differed between feeding and non-feeding periods. Each depth was represented by a distinct species community and was therefore affected differently by the feeding activity. At the surface, fish abundance was significantly higher during feeding compared with non-feeding periods. The distance from the feeding vessel significantly influenced fish aggregations in the water column, indicating that planktivorous species learnt to associate the boat noise with food availability through classic conditioning. At the bottom, substrate type was the dominant factor explaining aggregation variability. This study provides new information about the dynamics of fish aggregations within farms, emphasizing the importance of considering the different sources of variability in future study designs. [ABSTRACT FROM AUTHOR]

Individual foraging tactics are widespread in animals and have ecological and evolutionary implications. Indo-Pacific bottlenose dolphins ( Tursiops sp.) in Shark Bay, Western Australia, exhibit a foraging tactic involving tool use, called 'sponging.' Sponging is vertically, socially transmitted through the matriline and, to date, has been described in detail in the eastern gulf of Shark Bay ( ESB). Here, we characterize sponging in the western gulf of Shark Bay ( WSB), in which a different matriline engages in the behavior. We identified 40 individual 'spongers' in 9 mo of boat-based surveys over three field seasons. As is the case in ESB, the majority of WSB spongers was female and engaged in sponging in deep channel habitats. In contrast to ESB, however, there was no difference in the number of associates between spongers and nonspongers in WSB, and activity budgets differed between spongers and deep-water nonspongers; spongers foraged more frequently and rested less than nonspongers. Group sizes in deep channel habitat, where sponging was prevalent, were typically larger than those in shallow habitat, except for foraging, perhaps indicative of higher predator abundance and/or scattered prey distribution in deep-water habitat. This research improves our understanding of within-population foraging variations in bottlenose dolphins. [ABSTRACT FROM AUTHOR]

This study investigates the predation of P. noctiluca ephyrae on Atlantic Bluefin tuna (ABFT) eggs under different experimental conditions. The specific factors considered in the experimental design were: a) water mix conditions to explore predation under two-dimensional (2D) and three-dimensional (3D) prey distributions, b) prey density to investigate the ingestion rate capacity, and c) incubation time to inspect gut saturation. The eggs and jellyfish ephyrae were collected during the 2012 ABFT spawning survey off Ibiza (Balearic Isl., Western Mediterranean). The results showed that the proportion of feeding ephyrae increased with size. The mean clearance rate of feeding ephyrae, 4.14 L h-1, was the highest ever recorded for ephyrae. Under calm conditions the eggs floated at the surface (2D spatial arrangement) and the clearance rates, at low prey densities, were at least twice those under mixed conditions (3D spatial arrangement). At high prey density, clearance rate did not differ between mix conditions, probably due to the fast gut saturation, which was reached in c.a. 15 min, as revealed by time series observations of gut contents. The fast saturation of ephyrae and their slow digestion time of approximately 18 h suggest the existence of a diel feeding periodicity. We conclude that in the Western Mediterranean, P. noctiluca ephyrae are capable of predating on ABFT eggs, a highly pulsed and spatially restricted resource that potentially switches from a 3D to a 2D configuration in the absence of wind-generated turbulence. The P. noctiluca and Atlantic Bluefin tuna egg system might represent an example of a general mechanism linking pelagic and neustonic food webs. [ABSTRACT FROM AUTHOR]