Indonesian Manta Ray Habitat Use disturbance to this threatened species by tourism, regulations for the number of boats and interactions, especially during key reproductive times should be considered. Further, strict fishing regulation in the area is recommended as fishing gear entanglement was identified as a threat to this population.
Identifying appropriate management units is vital for wildlife management. Here we investigate one potential
management unit — resident communities of bottlenose dolphins — using information from ranging, occupancy, and
association patterns. We identify a resident community of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the
Swan Canning Riverpark, Western Australia based on: ranging patterns, sighting rates, Lagged Identification Rates
(LIR), and three measures of social affinity and structure (Simple Ratio Index, preferred dyadic association analyses,
and Lagged Association Rates (LAR)). The analyses yielded an estimated ‘community size’ of 17–18 individuals
(excluding calves). High seasonal sighting rates (> 0.75 sightings per season) and a long mean residence time (ca.
nine years) indicated year-round residency. The model best-fitting the LIR (emigration and mortality) also supported
this. The social structure of dolphins was species-typical, characterized by significant dyadic associations within agesex
classes (permutation test; P < 0.001), stronger associations among adult males than among adult females (LAR
males > LAR females), and temporally stable associations (LAR > null LAR). Constant companions or long-lasting
association models best explained adult male and female LARs. While behavioural information identified a resident
community in the Riverpark, genetic and demographic information is needed to assess its appropriateness as a
management unit.
Summary
Population structure must be considered when developing mark–recapture (MR) study designs as the sampling of individuals from multiple populations (or subpopulations) may increase heterogeneity in individual capture probability. Conversely, the use of an appropriate MR study design which accommodates heterogeneity associated with capture occasion varying covariates due to animals moving between ‘states’ (i.e. geographic sites) can provide insight into how animals are distributed in a particular environment and the status and connectivity of subpopulations.
The multistate closed robust design (MSCRD) was chosen to investigate: (i) the demographic parameters of Indo‐Pacific bottlenose dolphin (Tursiops aduncus) subpopulations in coastal and estuarine waters of Perth, Western Australia; and (ii) how they are related to each other in a metapopulation. Using 4 years of year‐round photo‐identification surveys across three geographic sites, we accounted for heterogeneity of capture probability based on how individuals distributed themselves across geographic sites and characterized the status of subpopulations based on their abundance, survival and interconnection.
MSCRD models highlighted high heterogeneity in capture probabilities and demographic parameters between sites. High capture probabilities, high survival and constant abundances described a subpopulation with high fidelity in an estuary. In contrast, low captures, permanent and temporary emigration and fluctuating abundances suggested transient use and low fidelity in an open coastline site.
Estimates of transition probabilities also varied between sites, with estuarine dolphins visiting sheltered coastal embayments more regularly than coastal dolphins visited the estuary, highlighting some dynamics within the metapopulation.
Synthesis and applications. To date, bottlenose dolphin studies using mark–recapture approach have focussed on investigating single subpopulations. Here, in a heterogeneous coastal–estuarine environment, we demonstrated that spatially structured bottlenose dolphin subpopulations contained distinct suites of individuals and differed in size, demographics and connectivity. Such insights into the dynamics of a metapopulation can assist in local‐scale species conservation. The MSCRD approach is applicable to species/populations consisting of recognizable individuals and is particularly useful for characterizing wildlife subpopulations that vary in their vulnerability to human activities, climate change or invasive species.
The forecast for the viability of populations depends upon metapopulation dynamics: the combination of reproduction and mortality within populations, as well as dispersal between populations. This study focuses on an Indo-Pacific bottlenose dolphin (Tursiops aduncus) population in coastal waters near Bunbury, Western Australia. Demographic modeling of this population suggested that recent reproductive output was not sufficient to offset mortality. Migrants from adjacent populations might make up this deficit, so that Bunbury would act as a "sink," or net recipient population. We investigated historical dispersal in and out of Bunbury, using microsatellites and mitochondrial DNA of 193 dolphins across five study locations along the southwestern Australian coastline. Our results indicated limited gene
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