Simon Northridge (Sea Mammal Research Unit, University of St Andrews, U.K.) and colleagues have reviewed causes of bycatch, including of seabirds, in gill net fisheries in the journal Conservation Biology.

The paper’s abstract follows:

“Gillnet fisheries are widely thought to pose a conservation threat to many populations of marine mammals, seabirds, and turtles. Gillnet fisheries also support a significant proportion of small-scale fishing communities worldwide. Despite a large number of studies on protected-species bycatch in recent decades, relatively few have examined the underlying causes of bycatch and fewer still have considered the issue from a multitaxon perspective. We used 3 bibliographic databases and one search engine to identify studies by year of publication and taxon. The majority of studies on the mechanisms of gillnet bycatch are not accessible through the mainstream published literature. Many are reported in technical papers, government reports, and university theses. We reviewed over 600 published and unpublished studies of bycatch in which causal or correlative factors were considered and identified therein 28 environmental, operational, technical, and behavioral factors that may be associated with high or low bycatch rates of the taxa. Of the factors considered, 11 were associated with potential bycatch reduction in 2 out of the 3 taxa, and 3 factors (water depth, mesh size, and net height) were associated with trends in bycatch rate for all 3 taxa. These findings provide a basis to guide further experimental work to test hypotheses about which factors most influence bycatch rates and to explore ways of managing fishing activities and improving gear design to minimize the incidental capture of species of conservation concern while ensuring the viability of the fisheries concerned.”

Read more on bycatch issues with gill nets in ACAP Latest News here.

References:

Northridge, S., Coram, A., Kingston, A. & Crawford, R. 2017.  Disentangling the causes of protected-species bycatch in gillnet fisheries.  Conservation Biology 31: 686-695.

Žydelis R., Small, C. & French, G. 2013.  The incidental catch of seabirds in gillnet fisheries: a global review.  Biological Conservation 162: 76-88.

John Cooper, ACAP Information Officer, 26 May 2017

Earlier this year ACAP attended the 12th Meeting of the Ecology Related Species Working Group (ERSWG 12) of the Commission for the Conservation of Southern Bluefin Tuna (CCSBT).  The meeting was held in Wellington, New Zealand over 21-24 March; ACAP was represented by Igor Debski, Vice-convenor of the ACAP Seabird Bycatch Working Group.

During the meeting seabirds and in particular seabird bycatch comprised an important part of the agenda, largely aimed to progress the assessment of the risks to ecological related species posed by fishing for Southern Bluefin Tuna Thunnus maccoyii (SBT).  Seabird matters addressed during the meeting included:

1. the status and trends of seabird species likely caught by SBT fisheries,
2. the process for the elaboration of an ecological risk assessment,
3. discussions on methods for calculating bycatch rates and total numbers of seabirds bycaught in SBT fisheries,
4. an update of the ACAP best-practice advice to mitigate seabird bycatch in pelagic longline fisheries, and
5. a review of tools and guidelines available for on-board observers, including the guide to improve seabird species identification developed by ACAP in collaboration with the Japan Fisheries Research Agency (now the National Research and Development Agency, Japan Fisheries Research and Education Agency).

Further collaboration between ACAP and CCSBT will include engagement with fishing nations to improve data collection, reporting and analysis, as well as providing advice during the process of developing a multi-year seabird strategy.  ACAP tabled several papers at the meeting as listed below:

• CCSBT-ERS/1703/15. (ACAP & BirdLife International) An update on the status and trends of ACAP-listed albatrosses and petrels in the CCSBT area.
• CCSBT-ERS/1703/16. (ACAP) The development of ACAP seabird bycatch indicators, data needs, methodological approaches and reporting requirements.
• CCSBT-ERS/1703/17. (ACAP) Current ACAP advice for reducing the impact of pelagic longline fishing operations on seabirds.
• CCSBT-ERS/1703/18. (ACAP and BirdLife International) Summary of tools and guidelines available to assist observers in the identification of seabird species and handling of bycaught individuals.

Igor Debski, Vice-convenor, ACAP Seabird Bycatch Working Group, 25 May 2017

Caroline Pott and David Wiedenfeld (American Bird Conservancy, The Plains, Virginia, USA) have reviewed information gaps in seabird bycatch in the journal Biological Conservation.

The paper’s abstract follows:

“Seabirds, as foragers in marine waters for at least part of their lifecycle, encounter the global fishing fleet in search of marine resources. While fishing gear is designed to catch fish and invertebrates, it also catches unintended species, including seabirds. We reviewed bycatch incidence for 378 marine and coastal bird species in 18 different gear types, and found that 60% (228 species) have been recorded interacting with at least one type of fishing gear. At least one species from each of the taxonomic groups analyzed (generally at the family level) has been documented interacting with fishing gear. With respect to two measures of degree of interaction, four families have a high degree of documented interaction: Gaviidae (loons or divers), Podicipedidae (grebes), Diomedeidae (albatrosses) and Sulidae (boobies and gannets). Set and drift gillnets (among the most studied gear types), have the greatest number of documented species interactions: 92 and 88 species, respectively. Hook gear (longlines and handlines) have documented interactions with 127 species. Together these four gear types have documented bycatch of 193 species. The waters of the Arctic, the Caribbean, the Guinea and Canary Currents in the Atlantic, the Indian Ocean and Asia have been poorly studied. Particular gear types, including industrially-deployed seines, and the artisanal fisheries sector also constitute significant gaps in our knowledge of seabird bycatch patterns worldwide.”

A bird-scaring line keeps seabirds at bay from the trawler warp, photograph by Leo Tamini 

With thanks to Caroline Pott: “Your news items were of great use to me when I was knee-deep in seabird lit research.”

Reference:

Pott, C. & Wiedenfeld, D.A. 2017.  Information gaps limit our understanding of seabird bycatch in global fisheries. Biological Conservation 210: 192-204.

John Cooper, ACAP Information Officer, 24 May 2018

Natalia Montesdeoca (Department of Animal Pathology, Veterinary Faculty, University of Las Palmas de Gran Canaria, Arucas, Las Palmas, Spain) and colleagues have published in the on-line journal PLoS ONE on seabirds, including Cory’s Shearwaters Calonectris borealis treated by a rehabilitation centre in the Canary Islands.

The paper’s abstract follows:

Aims

The aims of this study were to analyze the causes of morbidity and mortality in a large population of seabirds admitted to the Tafira Wildlife Rehabilitation Center (TWRC) in Gran Canaria Island, Spain, from 2003 to 2013, and to analyze the outcomes of the rehabilitation process.

Methods

We included 1,956 seabirds (133 dead on admission and 1,823 admitted alive) in this study. Causes of morbidity were classified into nine categories: light pollution (fallout), fishing gear interaction, crude oil, poisoning/intoxication, other traumas, metabolic/nutritional disorder, orphaned young birds, other causes, and unknown/undetermined. The crude and stratified (by causes of admission) rates of the three final disposition categories (euthanasia Er, unassisted mortality Mr, and release Rr), the time until death, and the length of stay were also studied for the seabirds admitted alive.

Results

Yellow-legged Gull (Larus michahellis) was the species most frequently admitted (46.52%), followed by Cory’s Shearwater (Calonectris diomedea borealis) (20.09%). The most frequent causes of morbidity were light pollution (fallout) (25.81%), poisoning/intoxication (24.69%), and other traumas (18.14%). The final disposition rates were: Er = 15.35%, Mr = 16.29%, and Rr = 68.34%. The highest Er was observed in the ‘other traumas’ category (58.08%). Seabirds admitted due to metabolic/nutritional disorder had the highest Mr (50%). The highest Rr was observed in the light pollution (fallout) category (99.20%).

Conclusions

This survey provides useful information for the conservation of several seabird species. We suggest that at least the stratified analysis by causes of admission of the three final disposition rates, and the parameters time until death and length of stay at the center should be included in the outcome research of the rehabilitation of seabirds. The high release rate for seabirds (68.34%) achieved at the TWRC emphasizes the importance of wildlife rehabilitation centers for the conservation of seabirds.

A fledgling Cory's Shearwater downed by city lights 

Reference:

Montesdeoca, N., Calabuig, P., Corbera, J.A. & Orós, J. 2017.  A long-term retrospective study on rehabilitation of seabirds in Gran Canaria Island, Spain (2003-2013).  PLoS ONE doi.org/10.1371/journal.pone.0177366.

John Cooper, ACAP Information Officer, 23 May 2017