A Campbell Albatross off North Cape, New Zealand; photograph by Kirk Zufelt

A report prepared by Vita Maris for New Zealand’s Department of Conservation titled, BCBC2020-11b: Development of bottom longline underwater setting devices, has been released by the Conservation Services Programme. 

Noting ACAP best practice guidelines on bottom long-line fishing which include the three mitigation measures of: night setting, line weighting, and tori lines, the authors signal advantages of underwater setters, including: reduced risk to birds, increased sink rates, and the potential of daytime setting for fishers.

The summary as follows:

“Estimated capture rates of at-risk seabirds by the small vessel demersal longline fleet are likely to be acceptable in the long term; both scientifically (e.g., Richard et al. 2017), and from a social ‘licence to operate’ perspective (e.g., RNZ, 2020), indicating the need for improvements in performance over and above that achievable using traditional mitigation measures.

The Agreement for the Conservation of Albatrosses and Petrels (ACAP) best practice guidance for bottom longline fishing includes use of the following three measures at all times: night setting, line weighting, and tori lines (ACAP, 2019). Setting lines for the ‘bite time’ over the change of light means many sets targeting snapper in the summer months do not meet the ACAP definition of best practice (Pierre et al., 2018). Additionally, the ACAP advice recognises that night setting may not be effective in bright moonlight, or for crepuscular/nocturnal foragers, and notes that mitigation measures need to be acceptable to fishers and not affect fish catch rates. Similarly, tori lines are often not fully effective to the prescribed aerial extent (pers. obs. DG).

The introduction of mitigation standards for demersal longliners (MPI, 2019) and subsequent changes to regulation (MPI 2021) require a hook depth of 5 m at the end of the tori line aerial extent, and likely require substantial changes to gear configuration and setting speed for some of the fleet (Goad & Olsen, 2022).

Underwater setting has the potential to increase sink rates and reduce risk to birds. It is particularly relevant to meeting the latest regulations and mitigation standards, whilst maintaining flexibility of gear configuration for fishers. It also has the potential to open up daytime setting in high-risk times and places.

Efforts to reduce the availability of pelagic longline hooks to birds has focused on increasing the sink rate of the hook, either mechanically (Gilman et al., 2003, Ryan & Watkins 2002, Robertson & Ashworth 2010), or by adding weight (e.g. Robertson 2013), or protecting the barb of the hook (Oceansmart, 2011, Hookpod, 2020). These ‘hook by hook’ approaches are feasible for pelagic longlines where branch lines are longer than 10 m, baited as they are set, set relatively slowly (e.g. Robertson 2013, Goad et al., 2019), and the hook sinks, certainly initially, independently from the mainline (Robertson et al., 2010).

Conversely, the inshore manual baiting demersal longline fleet in New Zealand clip on pre-baited hooks with short branchlines (or snoods), typically 0.6 m length, to a stoppered mainline relatively quickly (Goad et al., 2010). Therefore, in order to set demersal longlines underwater, both the hook and the mainline have to be deployed at depth. This presents a different set of challenges, and a downward force must be applied to the mainline in order to achieve sufficient depth.

This report describes work undertaken developing two underwater setting devices. The first was initially conceived by Dave Kellian, and is described here as the ‘underwater setter’. It is towed behind the vessel at depth and the longline passes under a guide. Previous work is described in Goad, 2011; Baker et al., 2013; 2016; and Goad et al., 2020. The second device was conceived by Nigel Hollands and uses a roller held under the surface by a pole fixed to the vessel, with the longline passing under the roller. It is described here as the ‘line depressor’ and previous work is described in Hollands et al., 2022.”

Reference:

Goad, D., Kiddie, B., Hollands, N., Clow, A., Angel, J. 2022. Development of bottom longline underwater setting devices. BCBC2020-11b final report prepared by Vita Maris for Department of Conservation, Wellington. 30 pp.

Posted 15 August 2022

Applications are open for ACAP’s 2022 Secondment Programme. Proposals should clearly address tasks contained within the work programmes of the Advisory Committee (see Annex 4, MoP7 Report) and Secretariat (see Annex 2, MoP7 Report), and aspire to foster capacity-building within Parties. Applicants are encouraged to develop proposals that account for any ongoing practical challenges and limitations associated with the COVID-19 pandemic.

Progress reports from previous secondments can be found at the ACAP website.

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Applications must be received by the ACAP Secretariat by close of business on Monday, 26 September 2022. Applicants will be advised of the outcome of their application by Tuesday, 8 November 2022.

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12 August 2022

 
Wandering Albatross at sunset, Île de la Possession, Crozet Islands; photograph by Franck Theron

Ruijiao Sun (Biology Department, Woods Hole Oceanographic Institution, Massachusetts, USA) and colleagues have published open access in the journal Ecological Monographs on life-history outcomes of a male-skewed population of Vulnerable Wandering Albatrosses Diomedea exulans on Île de la Possession, Crozet Islands, caused by fishery bycatch.

The paper’s abstract follows:

“Many animals form long-term monogamous pair bonds, and the disruption of a pair bond (through either divorce or widowhood) can have significant consequences for individual vital rates (survival, breeding, and breeding success probabilities) and life-history outcomes (lifetime reproductive success [LRS], life expectancy). Here, we investigated the causes and consequences of pair-bond disruption in wandering albatross (Diomedea exulans). State-of-the-art statistical and mathematical approaches were developed to estimate divorce and widowhood rates and their impacts on vital rates and life-history outcomes. In this population, females incur a higher mortality rate due to incidental fishery bycatch, so the population is male-skewed. Therefore, we first posited that males would show higher widowhood rates negatively correlated with fishing effort and females would have higher divorce rates because they have more mating opportunities. Furthermore, we expected that divorce could be an adaptive strategy, whereby individuals improved breeding success by breeding with a new partner of better quality. Finally, we posited that pair-bond disruptions could reduce survival and breeding probabilities owing to the cost of remating processes, with important consequences for life-history outcomes. As expected, we showed that males had higher widowhood rates than females and females had higher divorce rates in this male-skewed population. However, no correlation was found between fishing effort and male widowhood. Secondly, contrary to our expectation, we found that divorce was likely nonadaptive in this population. We propose that divorce in this population is caused by an intruder who outcompetes the original partner in line with the so-called forced divorce hypothesis. Furthermore, we found a 16.7% and 18.0% reduction in LRS only for divorced and widowed males, respectively, owing to missing breeding seasons after a pair-bond disruption. Finally, we found that divorced individuals were more likely to divorce again, but whether this is related to specific individual characteristics remains an important area of investigation.”

Reference:

Sun, R., Barbraud, C., Weimerskirch, H., Delord, K., Patrick, S.C., Caswell, H. & Jenouvrier, S. 2022.  Causes and consequences of pair-bond disruption in a sex-skewed population of a long-lived monogamous seabird.  Ecological Monographs  doi.org/10.1002/ecm.1522.

John Cooper, ACAP News Correspondent, 11 August 2022

White-chinned Petrel by ABUN artist Judith MacKay; after a photograph by Andy Wood

 Graeme Elliott and Kath Walker (Albatross Research) have reported to New Zealand’s Department of Conservation via its Conservation Services Programme (CSP) on a survey of globally Vulnerable White-chinned Petrels Procellaria aequinoctialis on Antipodes Island.

The final report’s abstract follows:

“During the summers of 2020-21 and 2021-22 the area of land occupied by white-chinned petrels on Antipodes Island was assessed along with burrow density and burrow occupancy which were combined to produce an estimate of the total size of the white-chinned petrel population there. This was compared with similar estimates made in 2008–2011, and the potential impact of landslides in 2014 and the eradication of mice from Antipodes I in 2016 on the current size of the white-chinned population was assessed. The most recent population estimate is larger than that made in 2008-2011, but the confidence intervals about both estimates are so large that it is not reasonable to conclude there has been any population change. The 2008–2011 and 2021–2022 estimates in combination suggest the population comprises ~46,000 breeding pairs.

The landslides in 2014 destroyed 5.6% of the white-chinned petrel burrows and as birds were incubating at the time of the landslides, up to 2.6% of the breeding population was killed. Subsequently the land on which the landslides occurred has been unsuitable for white-chinned petrel burrows and the birds that used these places have either died, moved, or stopped breeding.

Although mice are known to prey on white-chinned petrels, any improvement in nesting success because of the mouse eradication has not had sufficient time to be reflected in the size of the breeding population.

The use of distance sampling for assessing burrow density, as well as the explicit assessment of the effectiveness of burrow occupancy measurement techniques are useful improvements in white-chinned petrel population size assessment techniques. With greater field effort and increased sample sizes these tools could provide more precise estimates of population size, though even with these improvements, estimates of population size are not precise enough to reliably detect population trends. Detection of population change is likely to be more easily achieved with an intensive mark-recapture study of birds in a representative study population.”

Reference:

Elliot, G. & Walker K. 2022.  Estimating the number of white-chinned petrels breeding on Antipodes Island.  Nelson: Albatross Research.  17 pp.

John Cooper, ACAP News Correspondent, 10 August 2022