Towards the identification of ecological management units: A multidisciplinary approach for the effective management of bottlenose dolphins in the southern Iberian Peninsula

Abstract

Determining discrete and demographically independent management units within wildlife pop-ulations is critical for their effective management and conservation. However, there is a lack of consensus on the most appropriate criteria to delimit such management units. 2.A multi-disciplinary, multi-scale approach that combines tools informing in the short-term (i.e. photo-identification), with mid-term ecological tracers (stable isotopes -δ 13 C, δ 15 N and δ 34 Sand persistent organic pollutants -POPs-), and mid-to long-term genetic markers (microsatellites and mitochondrial DNA), was used to define management units within bottlenose dolphins (Tursiops truncatus) inhabiting the southern Iberian Peninsula. 3. Although genetically indistinguishable, individuals inhabiting the Strait of Gibraltar and the Gulf of Cadiz showed differences in their isotopic composition and the concentrations of certain POPs. Accordingly, the lack of photographic recaptures between the two sites pointed to the existence of at least two different ecological management units that segregate spatially and may require different conservation strategies. 4. Different time-scale approaches can reveal different management units. The results highlighted the use of medium-and short-term approaches for properly identifying ecologically different units for effective management and conservation. 5. Furthermore, these results have important management implications as European legislation promotes specific management plans for this species.

Fine‐scale population structure and connectivity of bottlenose dolphins, Tursiops truncatus, in European waters and implications for conservation

“…This information and existing estimates of abundance will help to evaluate the conservation status and vulnerability of the populations. The Gibraltar-Cadiz population included around 700 photo-identified individuals (Giménez et al, 2018) and the Pelagic Atlantic abundance estimates (from Scotland to Spain) are several tens of thousands of individuals (Hammond et al, , 2009) while the abundances of coastal dolphins do not exceed~400 individuals. Genetic diversity was higher in the pelagic populations than coastal populations as in previous studies (Hoelzel et al, 1998;Louis, Viricel, et al, 2014).…”

“…The Shannon population had the lowest genetic diversity and is the smallest with abundance estimated between 110 and 140 dolphins (Berrow, 2012;Englund, Ingram, & Rogan, 2008;Ingram & Rogan, 2002Rogan, Gkarakouni, Nykänen, Whitaker, & Ingram, 2018 TABLE 3 Mean (and 95% credible interval) recent migration rates inferred using BayesAss. stable isotopes and contaminant loads) and individual monitoring through photo-identification, leading to the delineation of two ecological, management units (Giménez et al, 2018). Migration rates above 0.10 have been highlighted in bold Cadiz, although potentially presenting no genetic structure, showed differences in ecology detected using different ecological tracers (i.e.…”

“…This is consistent with higher abundance of the pelagic populations compared with the coastal populations. The Gibraltar-Cadiz population included around 700 photo-identified individuals (Giménez et al, 2018) and the Pelagic Atlantic abundance estimates (from Scotland to Spain) are several tens of thousands of individuals (Hammond et al, , 2009) while the abundances of coastal dolphins do not exceed~400 individuals.…”

“…Furthermore, the criterion underlying GMUs is not entirely appropriate from a demographic point of view because migration rates (m) well below 10% can still lead to an absence of significant allelic differentiation (e.g. Giménez et al, 2018) or analyses of population viability (Olsen et al, 2014). Waples & Gaggiotti, 2006).…”

“…In addition, other measures can be used in order to define MUs, such as ecological tracers (e.g. Giménez et al, 2018) or analyses of population viability (Olsen et al, 2014).…”