Thomas Clay (School of Environmental Sciences, University of Liverpool, UK) and colleagues have published open access in the Journal of Animal Ecology on utilizing albatross and petrel bio-tracking data from South Georgia (Islas Georgias del Sur)* to identify “hot spot” overlaps with southern-hemisphere fisheries

The paper’s abstract follows:

“Incidental mortality (bycatch) in fisheries remains the greatest threat to many large marine vertebrates and is a major barrier to fisheries sustainability. Robust assessments of bycatch risk are crucial for informing effective mitigation strategies, but are hampered by missing information on the distributions of key life‐history stages (adult breeders and non‐breeders, immatures and juveniles).

Using a comprehensive biologging dataset (1,692 tracks, 788 individuals) spanning all major life‐history stages, we assessed spatial overlap of four threatened seabird populations from South Georgia, with longline and trawl fisheries in the Southern Ocean. We generated monthly population‐level distributions, weighting each life‐history stage according to population age structure based on demographic models. Specifically, we determined where and when birds were at greatest potential bycatch risk, and from which fleets.

Overlap with both pelagic and demersal longline fisheries was highest for black‐browed albatrosses, then white‐chinned petrels, wandering and grey‐headed albatrosses, whereas overlap with trawl fisheries was highest for white‐chinned petrels.

Hotspots of fisheries overlap occurred in all major ocean basins, but particularly the south‐east and south‐west Atlantic Ocean (longline and trawl) and south‐west Indian Ocean (pelagic longline). Overlap was greatest with pelagic longline fleets in May–September, when fishing effort south of 25°S is highest, and with demersal and trawl fisheries in January–June. Overlap scores were dominated by particular fleets: pelagic longline—Japan, Taiwan; demersal longline and trawl—Argentina, Namibia, Falklands, South Africa; demersal longline—Convention for Conservation of Antarctic Marine Living Resources (CCAMLR) waters, Chile, New Zealand.

Synthesis and applications.  We provide a framework for calculating appropriately weighted population‐level distributions from biologging data, which we recommend for future fisheries bycatch risk assessments. Many regions of high spatial overlap corresponded with high seabird bycatch rates recorded by on‐board observers, indicating that our approach reliably mapped relative bycatch risk at large spatial scales. Implementation of effective bycatch mitigation in these high‐risk regions varies considerably. Although potential bycatch risk appears to have decreased since the early 2000s, albatross and petrel populations from South Georgia and elsewhere are still declining, emphasizing the need for much improved observer coverage and monitoring of compliance with bycatch regulations.”

Wandering Albatross in the Drake Passage - one of the species studied; photograph by Kirk Zufelt

Reference:

Clay, T.A., Small, C., Tuck, G.N., Pardo, FD., Carneiro, A.P.B., Wood, A.G., Croxall, J.P., Crossin, G.T. & Phillips, R.A. 2019.  A comprehensive large‐scale assessment of fisheries bycatch risk to threatened seabird populations.  Journal of Applied Ecology https://doi.org/10.1111/1365-2664.13407.

John Cooper, ACAP Information Officer, 29 May 2019

*A dispute exists between the Governments of Argentina and the United Kingdom of Great Britain and Northern Ireland concerning sovereignty over the Falkland Islands (Islas Malvinas), South Georgia and the South Sandwich Islands (Islas Georgias del Sur y Islas Sandwich del Sur) and the surrounding maritime areas.

Lucas Krüger (Instituto Antártico Chileno, Punta Arenas, Chile) writes in the journal Polar Biology on trends in numbers of Southern Giant Petrels Macronectes giganteus breeding at an Antarctic site.

The paper’s abstract follows:

“In several parts of Antarctica, the information on the size of seabird populations is outdated by decades. Considering the environmental changes taking place at the Antarctic Peninsula, up-to-date information is urgently required. In this study, the breeding population of southern giant petrel (Macronectes giganteus) at Harmony Point, Nelson Island, was counted and mapped during incubation. The total number of active nests was 481, distributed mostly in small dispersed groups (< 30 nests); one single colony presented > 100 nests. Nests were distributed throughout the whole area. Current colony distribution was similar to the ones reported previously. The current number of nests is similar to those reported since 2005, and also for early counts in the 1965 and 1989s. However, current numbers were almost half of those counted in the 1997. The apparent increases in the number of southern giant petrels by 1997 was attributed to prohibiting tourism visits to the area (giant petrels are sensitive to human disturbance), but causes of the following decrease are unknown. This highlights the need for updated information in order to understand which factors are responsible for trends in Antarctic seabird populations.”

Southern Giant Petrels breeding in Antarctica, photograph from Maria Virginia Petry & Uwe Horst Schulz.

Reference:

Krüger, L. 2019.  An update on the Southern Giant Petrels Macronectes giganteus breeding at Harmony Point, Nelson Island, Maritime Antarctic Peninsula.  Polar Biology doi.org/10.1007/s00300-019-02504-5.

John Cooper, ACAP Information Officer, 28 May 2019

BirdLife South Africa is tackling the problem of designing bird-scaring lines (BSLs) for small (<35-m) longliners in the domestic fishery that are cheap, easy to deploy and less likely to get entangled than those made for deployment on larger vessels.  Use of BSLs is mandatory in South African longline (and trawl) fisheries.

Andrea Angel and Reason Nyengera of BirdLife South Africa’s Albatross Task Force (ATF) write in a recent blog

“Bird-scaring lines (BSLs) have become the primary and most commonly prescribed seabird bycatch mitigation measure in longline fisheries worldwide.  These are usually composed of a backbone section, colourful streamers and a drag section or towing device. They are extremely effective at reducing seabird bycatch since they scare foraging birds away from the “danger zone” in which baited hooks are close to the surface and easily accessible.  However, since BSLs have primarily been developed for and on large vessels, there is an urgent need to adapt them to the reality of small vessels and the fishing gear and conditions found on these. In South Africa our domestic longline fleets are largely under 35 m and while some skippers report successfully deploying BSLs on a regular basis, others have reported concerns relating to difficulties with deployments in bad weather conditions, entanglements with fishing gear, lack of high attachment points and unnecessarily cumbersome and bulky BSLs.”

A South African bird-scaring line is deployed behind a demersal trawler, keeping two Black-browed Abatrosses (and a Cape Gannet) away from the warp

BirdLife South Africa’s ATF has been working for over a decade with the Ocean View Association for Persons with Disabilities (OVAPD), which is based in the southern part of the Cape Peninsula near Cape Town, to manufacture BSLs of two different designs to keep birds away from demersal trawl cables and from longline fishing hooks on South Africa vessels.  The partnership brings meaningful employment to a disadvantaged community (click here).  OVAPD members will now be trained to manufacture the new design of BSLs, before they can be used commercially. Read earlier ALN postings on OVAPD here.

OVAPD members make a bird-scaring line

OVAPD members with Andrea Angel, Albatross Task Force Leader in South Africa (kneeling left)

Photographs from BirdLife South Africa's Albatross Task Force

BirdLife International and ACAP have co-produced a series of 15 Seabird Bycatch Mitigation Factsheets which describe the range of potential mitigation measures available to reduce seabird bycatch in longline and trawl fisheries, including different types of bird-scaring lines.

With thanks to Andrea Angel.

John Cooper, ACAP Information Officer, 27 May 2019

Morgan Gilmour (Ocean Sciences Department, University of California, Santa Cruz, California, USA) and colleagues have published in the journal Ecological Indicators on mercury and prolactin levels in Flesh-footed Shearwaters Ardenna carneipes (globally Near Threatened) and Great-winged Petrels Pterodroma macroptera.

The paper’s abstract follows:

“Marine predators are frequently exposed to contaminants through diet, and thus contaminants like mercury have the potential to be used as tracers of foraging ecology. Mercury’s neurotoxic and endocrine-disrupting effects can have far-ranging consequences for both individuals and populations, and thus mercury concentrations could also be indicative of wildlife health. Because blood samples are relatively non-invasive and easy to obtain in seabird colonies, we investigated whether blood-based mercury concentrations were representative of foraging ecology and breeding hormone concentrations in seabirds. Blood-based mercury carbon and nitrogen stable isotopes, and the reproductive hormone, prolactin, were sampled from two seabird species that exhibit different foraging strategies in Western Australia: Great-winged Petrels (Pterodroma macroptera) are pelagic squid-specialists whose populations are under-studied; Flesh-footed Shearwaters (Ardenna carneipes) are coastal foragers that associate with fishing vessels, and are a species listed as Vulnerable in Western Australia. Mercury was six times higher in Great-winged Petrels (geometric mean ± SE: 3.360 ± 0.180 μg g⁻¹ ww, n = 15) than Flesh-footed Shearwaters (0.554 ± 0.109 μg g⁻¹ ww, n = 12). There was a significant difference in δ¹⁵N between species, and within-species variation in δ¹³C mirrored variation in mercury concentrations, supporting the view that foraging ecology plays a central role in mercury exposure. Furthermore, Great-winged Petrels’ mercury concentrations are among the highest reported in seabirds. However, no relationship between mercury and prolactin concentrations was detected. Overall, these results demonstrate that mercury can be used as a foraging ecology tracer in these populations but may not be a good indicator of seabirds’ breeding hormones like prolactin, though mercury may affect other aspects of reproduction that we did not measure. These results may aid in future assessment of population trends in these, and other, species.

Flesh-footed Shearwater, photograph by Barry Baker

Reference:

Gilmour, M.E., Lavers, J.L., Lamborg, C., Chastel, O., Kania, S.A. & Shaffer, S.A. 2019.  Mercury as an indicator of foraging ecology but not the breeding hormone prolactin in seabirds.  Ecological Indicators 103: 248-259.

John Cooper, ACAP Information Officer, 24 May 2019