Conservation of transnational species: The tensions between legal requirements and best scientific evidence

Abstract

1. This paper describes the tensions between the legal requirements for conservation and the most beneficial biological practice for mobile transnational marine species, using the harbour porpoise (Phocoena phocoena) in European Atlantic waters as a case study. 2. Harbour porpoise are the smallest and one of the most abundant cetaceans occurring throughout the European continental shelf waters, and are affected by human activities occurring in the same waters, especially certain fishing activities. 3. The Convention on the Conservation of European Wildlife and Natural Habitats (the Bern Convention) and its implementing legislation the Council Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora 92/43/EEC (i.e. the Habitats Directive) are the main legal drivers for species conservation throughout the European Union. They aim for the long-term achievement of favourable conservation status and make provision for the use of two conservation measures: protected areas and strict protection measures. The strict protection measures aim to ensure that all forms of deliberate killing are prevented, and that where incidental killing and capture occurs, it does not have a negative effect on conservation status.4. The conservation of harbour porpoise is currently dependent upon tackling the key issue of bycatch in fisheries. However, in challenges to Member States on their application of the Habitats Directive, the European Commission has chosen to focus on site designation rather than the implementation of the strict protection measures required to monitor and, where necessary, reduce bycatch. 5. This tension between a legal focus on the designation of protected areas instead of tackling threats such as bycatch has potentially led to negative conservation consequences for harbour porpoise and, in part, may explain why wider marine biodiversity has continued to deteriorate in Europe.

Harbour Porpoise Abundance in Portugal over a 5-Year Period and Estimates of Potential Distribution

“…Despite the pressure for site designation in Portugal (which should have framed the application of a conservation plan), there have been no further measures effectively applied to promote the conservation of porpoises, which should have been focused on bycatch mitigation, to address the most important mortality source [ 7 ]. Similar situations have been described in other EU countries with respect to the conservation of transnational species [ 8 ].…”

“…Other important areas are visible in coastal areas south of Cape Carvoeiro (Peniche), south of Sines and around Cape São Vicente, although their importance varies between years. Nonetheless, marine protected areas are not useful to the conservation of the Iberian harbour porpoise unless monitoring and threat mitigation measures are put in place (see [ 8 ]).…”

Porpoises, by‐catch and the ‘pinger’ conundrum

“…The spatial and temporal variation in the distribution of porpoises and fishing effort, however, makes predicting the occurrence of by-catch inherently difficult. Although the conservation status of harbour porpoise is considered favourable for the European Atlantic region, the UK considers the conservation status to be unknown (JNCC, 2019;Pinn, Macleod & Tasker, 2021). This 'unknown' conclusion was drawn as a result of a decline in national abundance, although not statistically significant, and the lack of information regarding habitat quality.…”

“…This has been a particular concern when considering the use of pingers within protected areas specifically designated for the species. At the wider population scale, displacement is unlikely to be problematic given the large ranges of the animals and the habitat available, when compared with the area impacted by pinger noise (Sveegaard et al, 2011; Pinn, Macleod & Tasker, 2021). It is only where the movement of animals is constrained that displacement could become a potential conservation concern (Kyhn et al, 2015; Todd, Jiang & Ruffert, 2019).…”

“…However, banning static nets may also produce counter‐intuitive results because the fishing effort is not removed, only displaced. Where the displaced fishing vessels are moved to poorer grounds, there will be an increase in fishing effort, potentially leading to an increase in by‐catch outside the protected site boundaries (Pinn, Macleod & Tasker, 2021; Lusseau, Kindt‐Larsen & van Beest, 2023).…”