Human Interactions with Dusky Dolphins

Markowitz, Tim M.; Dans, Silvana Laura; Crespo, Enrique A.; Lundquist, David; Duprey, Nicholas M. T.

doi:10.1016/b978-0-12-373723-6.00011-4

Cited by 9 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Future work that compares current data with older data prior to the conservation regulations and fishing prohibitions will determine if the protocols have efficiently reduced anthropogenic impacts on the Kaikoura population. Future studies should assess threats in other geographic regions where dusky dolphins migrate to/from Kaikoura such as Admiralty Bay, which is subject to intense aquaculture (Markowitz et al, 2010a). Similar to the stock assessments conducted for false killer whales near Hawaii (Baird et al, 2014), further population estimates and health assessments need to be performed to determine whether the Kaikoura population is stable and "sustainable" or decreasing.…”

Section: Management Implicationsmentioning

confidence: 96%

“…comm.). Possible sources of fishing gear scars off Kaikoura include craypots, set nets, purse seines, hand-and longlines, and trawl nets (Markowitz et al, 2010a;Te Korowai o Te Tai ō Marokura, 2012). Craypot entanglement is an issue for migrating whales off Kaikoura as Table 4.…”

Section: Human Impactmentioning

confidence: 99%

“…There is a need for more information on the potential threats to dusky dolphins as current data is scarce (Markowitz et al, 2010a;Srinivasan & Markowitz, 2010). It is likely that many anthropogenic incidents with dusky dolphins are not reported and that many dead animals are not found.…”

Section: Introductionmentioning

confidence: 97%

“…In near-shore shallow waters, dolphin habitat use overlaps with areas of human recreational activities, increasing the risk of injuries to dolphins (Barr & Slooten, 1998;Weir et al, 2010). Dusky dolphins are at risk of propeller strikes when they approach vessels to ride bow waves (Markowitz et al, 2010a). Although commercial and recreational fishing activities are frequent off Kaikoura (Barr & Slooten, 1998;Duprey et al, 2008;Weir et al, 2008;Heinrich et al, 2010; Te Korowai o Te Tai ō Marokura, 2012), commercial bycatch rates of dolphins are reported to be low in New Zealand, with only six animals reported dead in local gillnets between 1997 and 2000 (Markowitz et al, 2010a).…”

Section: Introductionmentioning

confidence: 98%

“…Dusky dolphins are at risk of propeller strikes when they approach vessels to ride bow waves (Markowitz et al, 2010a). Although commercial and recreational fishing activities are frequent off Kaikoura (Barr & Slooten, 1998;Duprey et al, 2008;Weir et al, 2008;Heinrich et al, 2010; Te Korowai o Te Tai ō Marokura, 2012), commercial bycatch rates of dolphins are reported to be low in New Zealand, with only six animals reported dead in local gillnets between 1997 and 2000 (Markowitz et al, 2010a). As some dolphins migrate between different regions (Markowitz, 2004;Würsig et al, 2007), there may be more substantial threats from fisheries in other locations or along the migration pathway.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Sources of Notch and Scar Patterns on the Dorsal Fins of Dusky Dolphins (Lagenorhynchus obscurus)

Kügler¹

2014

Aquat Mamm

View full text Add to dashboard Cite

Few studies have investigated the origins of distinctive marks on cetaceans and quantitatively evaluated the causal factors. We used photo-identification data to categorize the ecological sources of scars and notches on the dorsal fins of freeranging dusky dolphins (Lagenorhynchus obscurus) off Kaikoura, New Zealand. Dorsal fin photographs of 1,171 individuals that had marks from ecological sources were collected from October 2011 through January 2012. Photographs of scars and notches were compared to marks of known origin, cross-validated by experts, and categorized as derived from conspecifics, killer whales, sharks, vessel strikes, fishing gear, or unknown. A total of 1,019 dusky dolphins had notches, of which 419 (41%) individuals had additional scars. A smaller subset of dolphins (152 individuals) had only scars or pigmentations as marks. The marks on the majority of dusky dolphins were attributed to intraspecific interactions (notches: 84%, n = 983; scars: 30%, n = 355). Indications of predation attempts (sharks: 0.17%, n = 2; killer whales: 0.09%, n = 1; unclassified natural predators: 0.26%, n = 3) and human impact (net/line: 0.43%, n = 4; vessel: 0.17, n = 2; unclassified human impact: 0.34%, n = 4) were comparatively low. These results are consistent with previous studies and indicate that most marks on dusky dolphins are caused by conspecifics and that predation pressure and bycatch rates are low off Kaikoura. We suggest that these data indicate that current management actions regulating commercial and recreational boating activities in the area are sufficient, with no need for immediate modification.

show abstract

Section: Management Implicationsmentioning

confidence: 96%

Section: Human Impactmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Sources of Notch and Scar Patterns on the Dorsal Fins of Dusky Dolphins (Lagenorhynchus obscurus)

Kügler¹

2014

Aquat Mamm

View full text Add to dashboard Cite

show abstract

Dusky Dolphins of Continental Shelves and Deep Canyons

Pearson

2019

Ethology and Behavioral Ecology of Odontocetes

View full text Add to dashboard Cite

Seasonal flow dynamics exacerbate overlap between artisanal fisheries and imperiled Ganges River dolphins

Paudel

Koprowski

Cove

2020

Sci Rep

View full text Add to dashboard Cite

Here we quantify the effects of artisanal fisheries on the ecology of a small cetacean, the Ganges River dolphin (Platanista gangetica gangetica, GRD), in a large river system of Nepal. We examine the size-classes of fisheries’ catches, behavioural changes in GRD in response to fishing activities, and diel overlap between GRD and fishing activity. We observed high human exploitation rates (> 60% of the total catch per effort) of GRD-preferred prey sizes, indicating risks of high resource competition and dietary overlap, especially during the low water season when resource availability is reduced. Competitive interactions in the feeding niches during the low water season, plus temporal overlap between the peak exploitation and critical life-history events (e.g., reproduction), likely have ecological consequences. Furthermore, we detected 48% (95% CI 43–52%) increase in the chance of behavioural changes among dolphins exposed to anthropopressure (fishing activity), risking social behaviour impairment in exposed dolphins. The higher diel overlap and increased diel coefficient as the surveys progressed towards the monsoon season suggest temporal shifts in GRD socio-behavioural states and seasonal effects on resource partitioning, respectively. This work identifies drivers of small cetaceans-fisheries interactions and their consequences, and can be used to help reduce biologically significant fishing impacts on small cetaceans. Mitigation strategies, together with river sanctuary and distanced-based approaches, should be urgently included in a framework of ecosystem-based management.

show abstract

Human Interactions with Dusky Dolphins

Cited by 9 publications

References 0 publications

Sources of Notch and Scar Patterns on the Dorsal Fins of Dusky Dolphins (Lagenorhynchus obscurus)

Sources of Notch and Scar Patterns on the Dorsal Fins of Dusky Dolphins (Lagenorhynchus obscurus)

Dusky Dolphins of Continental Shelves and Deep Canyons

Seasonal flow dynamics exacerbate overlap between artisanal fisheries and imperiled Ganges River dolphins

Contact Info

Product

Resources

About