Male gray seals specialize in raiding salmon traps

Königson, Sara; Fjälling, Arne; Berglind, Malin; Lunneryd, Sven-Gunnar

doi:10.1016/j.fishres.2013.07.014

Cited by 42 publications

(48 citation statements)

References 18 publications

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“…Seals bycaught in static gear are most often juveniles or young adults (Bäcklin et al, 2011). Königson et al (2013) found that some grey seals specialize in raiding static fishing gear such as salmon trap-nets, and that these tend to be adult males in particular. These rogue seals return repeatedly to catch salmon and are apparently experienced with the fishing gear and know how to avoid getting caught.…”

Section: Discussionmentioning

confidence: 99%

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Seal exclusion devices in cod pots prevent seal bycatch and affect their catchability of cod

et al. 2015

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Section: Discussionmentioning

confidence: 99%

“…In average they had 55 fishing trips in 2009 and 45 trips in 2010. Königson et al (2013) showed that a fisherman using 120 pots can get viable commercial catches. Results from this study show that the average bycatch frequency for area 1, 2 and 3 is one seal per 408 unit efforts when pots without SED are used.…”

Section: Discussionmentioning

confidence: 99%

Seal exclusion devices in cod pots prevent seal bycatch and affect their catchability of cod

et al. 2015

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“…For example, in the Baltic Sea set-trap salmon fisheries, seal presence was estimated to account for 37%-46% more catch loss than that estimated from partially consumed catch alone (Fjälling, 2005). Given the proven importance of underwater imagery to understand the extent of seal depredation in other fisheries (Königson et al, 2003(Königson et al, , 2013, we believe that DIDSON will have much broader application in the future study and mitigation of marine mammal interactions with fisheries. Similar modifications have been attempted in Baltic Sea trap fisheries with some success (Lehtonen & Suuronen, 2004).…”

Section: Figurementioning

confidence: 99%

“…Königson et al, 2013) prevented the use of statistical inference to further explore diel patterns. The opening, or "mouth" of the catch chamber, or "bowl" is visible at the top of the image, as is the netting of the "heart" and bowl extending away from the poles on either side of the mouth (ca.…”

Section: Figurementioning

confidence: 99%

“…Research was recommended to undertake a stepwise, sequential approach, with experiments and field trials of depredation reduction methods following documentation of the nature, extent, and costs of depredation. Seal depredation has been well documented in Baltic Sea trap fisheries (e.g., Kauppinen et al, 2005;Königson et al, 2007), where underwater imagery has proven valuable in documenting species and behavior of seals engaged in depredation of catches in fyke nets and salmon traps (Königson et al, 2003(Königson et al, , 2013. Seal depredation has been well documented in Baltic Sea trap fisheries (e.g., Kauppinen et al, 2005;Königson et al, 2007), where underwater imagery has proven valuable in documenting species and behavior of seals engaged in depredation of catches in fyke nets and salmon traps (Königson et al, 2003(Königson et al, , 2013.…”

Section: Introductionmentioning

confidence: 99%

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Gray Seal Behavior in a Fish Weir Observed Using Dual-Frequency Identification Sonar

Nichols¹,

Eldredge²,

Cadrin³

2014

mar technol soc j

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A B S T R A C TMarine mammal depredation can have significant negative effects on the performance of fixed fishing gears. Gray seals (Halichoerus grypus grypus) have been observed feeding on fish weir catches in Nantucket Sound, and remnants of longfin inshore squid (Doryteuthis pealeii ) and finfish in the nets are attributable to seal depredation. A dual-frequency identification sonar (DIDSON) deployed in a weir to monitor squid and fish occurrence captured observations of seal presence and behavior. Continuous recordings of 24+ h were subsampled at multiple intervals to optimize the likelihood of seal detection while minimizing processing time. Targets detected and identified to species included squid, bluefish (Pomatomus saltatrix), and gray seals. Seal occurrence in the weir was observed primarily at night. The presence and behavior of seals may negatively affect the efficiency of the weir due to disruption of the passage of schooling squid and finfish into the catch chamber. Behavioral observations collected using DIDSON can aid in the design of fishing gear modifications to reduce seal depredation.

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Behavioural heterogeneity across killer whale social units in their response to feeding opportunities from fisheries

Auguin,

Guinet,

Mourier

et al. 2024

Ecology and Evolution

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Intra‐population heterogeneity in the behavioural response of predators to changes in prey availability caused by human activities can have major evolutionary implications. Among these activities, fisheries, while extracting resources, also provide new feeding opportunities for marine top predators. However, heterogeneity in the extent to which individuals have responded to these opportunities within populations is poorly understood. Here, we used 18 years of photo‐identification data paired with statistical models to assess variation in the way killer whale social units within a subantarctic population (Crozet Islands) interact with fisheries to feed on fish caught on fishing gear (i.e., depredation behaviour). Our results indicate large heterogeneity in both the spatial and temporal extents of depredation across social units. While some frequently depredated on fishery catches over large areas, others sporadically did so and in small areas consistently over the years. These findings suggest that killer whale social units are exposed to varying levels of impacts of depredation, both negative (potential retaliation from fishers) and positive (food provisioning), on their life history traits, and may explain the contrasted demographic patterns observed within the declining population at Crozet but also potentially within the many other killer whale populations documented depredating on fisheries catches worldwide.

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Male gray seals specialize in raiding salmon traps

Cited by 42 publications

References 18 publications

Seal exclusion devices in cod pots prevent seal bycatch and affect their catchability of cod

Seal exclusion devices in cod pots prevent seal bycatch and affect their catchability of cod

Gray Seal Behavior in a Fish Weir Observed Using Dual-Frequency Identification Sonar

Behavioural heterogeneity across killer whale social units in their response to feeding opportunities from fisheries

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