Rodent eradication could be at least 10 times more cost effective than area closures in conserving seabird populations affected by Australia’s Eastern Tuna and Billfish Fishery (ETBF).

While not directly reducing bycatch, a biodiversity offset system of this nature may be more cost effective than a fishery closure as an interim measure while longer term solutions are being developed.

Biodiversity offsets – actions at one site that compensate for losses at another – have been advocated as a means of conserving seabird species that are caught as bycatch in ocean fisheries.  As part of their Marine Biodiversity Hub research, Sean Pascoe and Chris Wilcox of CSIRO, and Josh Donlan of Conservation Strategies and Cornell University, have examined their potential use in the ETBF, which historically has an annual catch of up to 4,500 flesh-footed shearwaters (Puffinus carneipes) - a species listed under marine and migratory species in the Environment Protection and Biodiversity Conservation Act.

The shearwaters breed on Lord Howe Island and forage in areas of high fishing activity. They also face threats such as habitat loss, ingestion of plastic, and predation by invasive predators.

“Efforts to reduce fisheries bycatch are improving, but they are costly and difficult to enforce,” Pascoe says. “Fishery area closures are one possibility, but these impose substantial costs on the industry through loss of access to key fishing grounds.

“Previous modelling suggests that even modest predation rates by invasive species such as rats may have a significant impact on the seabird population.

“This suggests greater reductions in mortality (and greater benefits) could potentially be achieved by re-focusing attention away from a fishery-based solution to other conservation activities: such as the eradication of invasive species, or the creation of new (or restoration of old) breeding habitats.”

Pascoe and his colleagues built on earlier modelling work of a colony of seabirds that interacts with both fishers and an invasive species. They compared the relative costs and conservation benefits of a fishery area closure and invasive species eradication, allowing bycatch technical solutions to be developed over time.

They found that biodiversity offsets may play an important role as a ‘stop-gap’ measure to provide initial relief where seabird populations have threats other than fishing affecting their populations.

While these may not be an appropriate long term solution, they may remove the need for more drastic and costly measures (such as fishery closure) in the short term.

The mechanism used to fund biodiversity offsets could be individual vessel levies for bycatch. This would provide regulatory certainty for operators; create incentives for fishers to avoid bycatch; fund mitigation actions that at least partially offset the bycatch; and potentially fund the development of bycatch reduction technologies.  These and similar actions would support the Lord Howe Island Biodiversity Management Plan (NSW DECC 2007) and the Threat Abatement Plan for the Incidental Catch (or Bycatch) of Seabirds During Oceanic Longline Fishing Operations (AAD 2006).

The principles could be extended to different offsetting approaches such as habitat restoration or creation, and several species and broader ecosystems would benefit from the removal of invasive mammals and other on-island restoration actions.  The NERP Marine Biodiversity Hub is researching how offsets could be used more broadly in managing the marine environment.

Source:
Pascoe S., Wilcox C., Donlan C.J. (2011) Biodiversity Offsets: A Cost-Effective Interim Solution to Seabird Bycatch in Fisheries? PLoS ONE 6(10)

Photo:  Bird hooked.  (Ed Melvin, NOAA; Jennifer Lavers. 2007)