Predators on marine fish farms in Tasmania

Pemberton, David; Brothers, Nigel; Copson, GR

doi:10.26749/rstpp.125.33

Cited by 9 publications

(16 citation statements)

References 2 publications

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“…Prey remains are often recovered when seals target fish in trawl nets or aquaculture pens (Kemper et al 2003). Australian fur seals have been found to leave parallel striations and puncture wounds on fish caused by penetration of prey items with their long canine teeth during biting (Pemberton et al 1991). In contrast to fur seals, harbor seals have been found to bite open the abdomen to remove the liver and 580 stomach of fish prey (Rafferty et al 2012).…”

Section: Discussionmentioning

confidence: 99%

Prey capture and processing behaviors vary with prey size and shape in Australian and subantarctic fur seals

Hocking

Fitzgerald

Salverson

et al. 2015

Marine Mammal Science

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When hunting at sea, pinnipeds should adapt their foraging behaviors to suit the prey they are targeting. We performed captive feeding trials with two species of otariid seal, Australian fur seals (Arctocephalus pusillus doriferus) and subantarctic fur seals (Arctocephalus tropicalis). This allowed us to record detailed observations of how their foraging behaviors vary when presented with prey items that cover the full range of body shapes and sizes encountered in the wild. Small prey were captured using suction alone, while larger prey items were caught in the teeth using raptorial biting. Small fish and long skinny prey items could then be swallowed whole or processed by shaking, while all prey items with body depths greater than 7.5 cm were processed by shaking at the water's surface. This matched opportunistic observations of feeding in wild Australian fur seals. Use of “shake feeding” as the main prey processing tactic also matches predictions that this method would be one of the only tactics available to aquatic tetrapods that are unable to secure prey using their forelimbs.

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Section: Discussionmentioning

confidence: 99%

Prey capture and processing behaviors vary with prey size and shape in Australian and subantarctic fur seals

Hocking

Fitzgerald

Salverson

et al. 2015

Marine Mammal Science

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“…The concentration of abundant potential food within fish farms is a major attraction to piscivorous predators and results in a significant management problem for fish farmers (Ross 1988, Pemberton et al 1991. In the northern and southern hemisphere seals are the most prevalent predators at fish farms (Hawkins 1985, Ross 1988, Pemberton & Shaughnessy 1993.…”

Section: Introductionmentioning

confidence: 99%

“…In the northern and southern hemisphere seals are the most prevalent predators at fish farms (Hawkins 1985, Ross 1988, Pemberton & Shaughnessy 1993. The Australian fur seal (Arctocephalus pusillus doriferus) is the main predator interacting with salmonid fish farms in Tasmania (Pemberton et al 1991).…”

Section: Introductionmentioning

confidence: 99%

Trapping and relocating seals from salmonid fish farms in Tasmania, 1990-2000: was it a success?

Hume¹,

Pemberton²,

Gales³

et al. 2002

PPRST

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In an effort to reduce the impact of seals on fish farms, the trapping and relocation of seals at Tasmanian salmonid farms began in 1990. To the end of May 2000, 353 identified individual seals had been trapped in 672 capture events. Most were non-breeding male Australian fur seals (Arctocephalus pusillus doriferus). The number of seals captured increased (from four in 1990 to a peak of 164 in 1998) with the size and extent of the farms, and an increase in salmon production from 55 tonnes in 1986/87 to almost 10 000 tonnes in 1999/2000. Of 586 capture events 52% were of seals that had been captured more than once. When seals are recaptured following trapping and relocation, this occurs on average 25 days after capture. Capture-mark-recapture calculations show that many seals in the viciniry of fish farms are not 'trappable', suggesting that trapping is only effective for certain individuals. Some individuals are recaptured many times, reflecting the predisposition of some individuals to be captured ('trap-happy'). Interaction is seasonal, with most seals trapped during winter, between May and September. The assessment of trends in capture rates is problematic, due to the lack of capture effort information from the farms. A further confounding factor has been the change in management practice both between farms and over time, as the use of predator nets has become more widespread. Two seals trapped at fish farms and fitted with satellite transmitters before relocation have either not returned to the farm or returned to the vicinity of farms and not interacted with them, although on one occasion the individual was trapped. The effectiveness of the relocation program as a management tool to reduce seal interactions cannot be quantified from the relocation data per se, bur relocation does not stop seals interacting with farms.

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“…), and common bottlenose dolphins (Tursiops truncatus) (Díaz López, 2006b;Díaz López, 2012) in the vicinity of fish farms, causing occasional conflicts with the industry (Würsig & Gailey, 2002;Kemper et al, 2003;Díaz López & Shirai, 2007;Díaz López, 2012). This is because marine top predators such as dolphins may take fish from sea cages and sometimes scare the farmed fish, thereby increasing their susceptibility to different diseases and reducing their growth rate as a result of stress (Pemberton, Brothers & Copson, 1991;Price & Nickum, 1995;Díaz López, 2006b;Vilata, Oliva & Sepulveda, 2010). Furthermore, dolphins may also face other potential risks derived from such interaction beyond intentional killing (Notarbartolo di Sciara & Bearzi, 2002), namely entanglement (Würsig & Gailey, 2002;Díaz López & Shirai, 2007), habitat exclusion (Watson-Capps & Mann, 2005), hearing damage, habitat avoidance, and the masking of important biological sounds caused by aversive acoustic devices (Olesiuk et al, 2002;Fjälling, Wahlberg & Westerberg, 2006;Díaz López & Mariño, 2011;Todd, Jiang & Ruffert, 2019), habitat degradation, and the alteration of natural behaviour (Díaz López, 2009).…”

Section: Introductionmentioning

confidence: 99%

Common bottlenose dolphin (Tursiops truncatus) interaction with fish farms in the Gulf of Ambracia, western Greece

Andrés

Cardona

Gonzalvo

2021

Aquatic Conservation

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1. Marine aquaculture, and its fast-growing development, has the potential for wider environmental, ecosystem, and biodiversity impacts. This study assesses the impact of fish farming on a bottlenose dolphin (Tursiops truncatus) population within the Gulf of Ambracia (western Greece) between 2007 and 2018. Two different study areas were defined in order to investigate differences on occurrence, abundance, behaviour, and seasonal fluctuations between them: a 'control area', in the north-western side of the Gulf; and a 'fish farm area', in the south west, where the highest density of fish farm cages is found.2. A total of 169 daily surveys were dedicated to the control area and 74 days were dedicated to the fish farm area, yielding 104 and 37 sightings, respectively. Both the probability of detecting dolphins (U = 6,763.000, P = 0.002) and the group sizes (U = 578.000, P < 0.001) were smaller around fish farms.3. Seasonality analyses were restricted to 2007-2008, as this was the period with year-round effort. Results revealed that dolphins were more frequently seen around fish farms in the winter (Kruskal-Wallis test, P = 0.036).4. From the 40 identified individuals that were re-sighted at least 10 times during the study period, 21 used the fish farm area less than expected according to sampling effort, and 10 of them were never observed in that area (binomial test, P < 0.05).5. The results revealed an impact of fish farms on the distribution of bottlenose dolphins in the Gulf of Ambracia. This information should be taken into consideration when defining ecosystem-based management measures within the management plan, which is currently in preparation for this Natura 2000 site.

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Predators on marine fish farms in Tasmania

Cited by 9 publications

References 2 publications

Prey capture and processing behaviors vary with prey size and shape in Australian and subantarctic fur seals

Prey capture and processing behaviors vary with prey size and shape in Australian and subantarctic fur seals

Trapping and relocating seals from salmonid fish farms in Tasmania, 1990-2000: was it a success?

Common bottlenose dolphin (Tursiops truncatus) interaction with fish farms in the Gulf of Ambracia, western Greece

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