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

Lucía Soliño (Instituto Português do Mar da Atmosfera, Lisbon, Portugal) and colleagues have published in the journal Harmful Algae on whether harmful algal blooms can affect pelagic seabirds, such as Cory’s Calonectris borealis and Scopoli’s C. diomedea Shearwaters.

The paper’s abstract follows:

“Marine birds have been hypothesized to be underreported victims of harmful algal blooms (HABs). Toxic blooms of Pseudo-nitzschia spp., the primary amnesic toxin producer microalgae, domoic acid (DA) are known to cause massive mortalities of coastal seabirds and marine mammals around the world. However, these fatalities are only detected when birds die nearby the coastline and little is known about possible outbreaks of pelagic seabirds in oceanic areas. Here we aim to understand whether pelagic seabirds are exposed to amnesic shellfish poisoning (ASP) toxins. For this purpose, we tracked pelagic seabirds feeding on small epipelagic fish and squid, reported to be vectors of DA, which are obtained in high productivity zones where intense Pseudo-nitzschia blooms regularly occur. In particular, we tracked Cory’s (Calonectris borealis) and Scopoli’s (C. diomedea) shearwaters breeding in Gran Canaria (Canary Is.) and in Menorca (Balearic Is.) and feeding on the Canary Current region and the Catalonian coast, respectively. We sampled birds for blood at the recovery of the GPS (Global Positioning System) and analyzed it for DA determination by Liquid Chromatography coupled with Tandem Mass Spectrometry (LC–MS/MS). Among the 61 samples analyzed from Gran Canaria, and 87 from Menorca, 31 (50.8%) and 28 (32.2%) from each location presented detectable levels of DA ranging 1.0–10.6 ng mL⁻¹. This work reveals that DA can be detected at variable levels in the blood of ASP-asymptomatic shearwaters and suggests a chronic exposure of shearwaters to DA, highlighting the need for further studies on DA effects. These results are of high relevance due to the vulnerability of these marine birds, which populations are in continuous decline. Since global warming is expected to alter and increase the occurrence of HABs, marine toxins might become an additional stressor for seabirds and exacerbate the already precarious conservation status of many species.”

Scopoli's Shearwater, photograph by 'Pep' Arcos

Reference:

Soliño, L., Ferrer-Obiol, J., Navarro-Herrero, L. González-Solís, J. & Costa, P.R. 2019.  Are pelagic seabirds exposed to amnesic shellfish poisoning toxins?  Harmful Algae 84: 172-180.

John Cooper, ACAP Information Officer, 23 May 2019

Ben Dilley (FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch, South Africa) and colleagues have published in the journal Ardea on three species of burrowing petrels at Marion Island competing for burrows, including two ACAP-listed Procellaria petrels.

The paper’s abstract follows:

“Competition for nest sites is relatively common amongst burrow-nesting Procellariiformes, especially on some sub-Antarctic islands where there is limited availability of good burrow-nesting habitat. Where space is limited, petrels may even successfully share a common burrow entrance or nest chamber and burrow densities can reach >7000 burrows/ha. Interspecies burrow competition and chick evictions generally occur as a result of an overlap in breeding seasons, yet there are few documented records of this behaviour and even within study colonies many evictions are unconfirmed or probably go undetected. Here we report on interactions among three burrow-nesting petrels (White-chinned Petrels Procellaria aequinoctialis, Grey Petrels P. cinerea and Great-winged Petrels Pterodroma macroptera) at Marion Island which we observed through regular nest checks with a burrowscope and using infra-red video cameras inside burrow chambers. Despite relatively low petrel densities, White-chinned Petrels were responsible for 17% (8/46) of the Great-winged Petrel chick mortalities over the five breeding seasons (3% of the breeding attempts), but two were also recorded feeding Great-winged Petrel chicks. A pair of White-chinned Petrels evicted a Grey Petrel chick, but then had their own chick killed by Grey Petrels the following season, who went on to breed successfully in the same burrow. Feral Cats Felis catus were eradicated in 1991 and the greatly reduced petrel populations are slowly recovering, which could exacerbate competition for burrows on Marion.”

White-chinned Petrel with a 97-day old Great-winged Petrel chick it had killed, photograph by Ben Dilley

 Supplementary video at https://youtu.be/OyeSBDW8tqg of a White-chinned Petrel kiling a 30-day old Great-winged Petrel chick.

With thanks to Ben Dilley.

Reference:

Dilley, B.J., Davies, D., Stevens, K., Schoombie, S., Schoombie, J. & Ryan, P.G. 2019.  Burrow wars and sinister behaviour among burrow-nesting petrels at sub-Antarctic Marion Island.  Ardea 107: 97-102.

John Cooper, ACAP Information Officer, 22 May 2019