Do abundance–occupancy relationships exist in cetaceans?

Abstract

A positive relationship between the number of locations where a species occurs and the average density of individuals across those locations has been found in a wide variety of taxa and has been described as one of the most general and widespread relationships in macro-ecology. However, exceptions to this general rule have been found and this study tested whether abundance–occupancy relationships exist within the cetacean community of the west coast of Scotland. Data were collected in 2003–2006 and occupancy rates were calculated and compared to two density indices (relative density of groups per km2 surveyed and relative density of individuals per km2 surveyed) for four cetacean species (harbour porpoise, bottlenose dolphin, common dolphin and minke whale). Significant positive intraspecific abundance–occupancy relationships were found for both relative density of groups per km2 and relative density of individuals per km2 for two out of the four cetacean species tested (harbour porpoise and minke whale). When the relationships between the different species were compared, all four were found to conform to the same interspecific relationship when relative density of groups was used as the density index. However, some species were found to conform to different relationships when relative density of individuals was used as the density index, potentially due to differences in social structure between cetacean species. These relationships mean that when cetaceans are at a higher density within an area, they also occupy a greater number of locations and vice versa. The existence of positive abundance–occupancy relationships in cetaceans has a number of potential implications for their conservation and management. In particular, it means that when a potential impact is likely to positively or negatively affect the size of the range of a species or population, such as noise pollution or climate change, it is likely to also affect the species' or population's abundance in the same direction. It also has implications for the design and extent of protected areas, such as marine protected areas; as such relationships could be used to determine the area required to maintain a viable population size.

Estimating Cetacean Carrying Capacity Based on Spacing Behaviour

“…The constant AOR relationship found for humpback whales in the Gulf is different to other cetacean species investigated [44], which tend to show a positive AOR. This could reflect the difference in the population’s situation at the time of study; for example, the Minke whales ( Balaenoptera acutorostrata ) were analysed while they were foraging [44], whereas the humpback whales in this study were not feeding and so distributions were not driven by food patchiness.…”

“…This could reflect the difference in the population’s situation at the time of study; for example, the Minke whales ( Balaenoptera acutorostrata ) were analysed while they were foraging [44], whereas the humpback whales in this study were not feeding and so distributions were not driven by food patchiness. The consequence to having a constant AOR is that as more whales enter the Gulf, the Gulf becomes increasingly dense.…”

“…In the basic AOR pattern, density remains constant while the occupied area increases, meaning that abundance increases in proportion to the area. However, for most species the AOR is positive; as the density increases so does the occupied area [40]–[44]. In these cases, the population size is increasing at a greater rate than would be expected simply by a range expansion.…”

Influence of seasonality on cetacean diversity, abundance, distribution and habitat use in the western Mediterranean Sea: Implications for conservation

“…To investigate environmental determinants of species hot spots during different seasons to provide insight into the ecological processes that produce seasonal patterns of distribution, the Generalized Additive Model (GAM, Hastie & Tibshirani, ) was performed as an explanatory model on the seasonal presence/absence of fin whale, striped dolphin and squid eaters. The semi‐parametric GAM was chosen since it can deal with unknown, non‐linear, and non‐monotonic relationships between the response and the set of explanatory variables (Guisan, Edwards, & Hastie, ; Hall et al ., ; Redfern et al ., ), and it is recommended for data that are systematically recorded and collected within the same protocol (Correia, Tepsich, Rosso, Caldeira, & Sousa‐Pinto, ; Praca, Gannier, Das, & Laran, ). GAM was similarly applied to the investigated species/seasons to assess seasonal differences in relation to the main topographic features (depth, slope, distance from the coast, aspect easting, and aspect northing).…”

Validating metabarcoding-based biodiversity assessments with multi-species occupancy models: A case study using coastal marine eDNA

“…Our model did not consider false positives, and, to our knowledge, these have yet to be incorporated into multi-species occupancy models. Following current protocols, abundance estimates from metabarcoding data are not reliable [55,56], but occupancy models can provide a means to estimate trends in abundance from the presence-absence data generated by metabarcoding based on documented relationships between occupancy and abundance [57][58][59]. The hierarchical modeling framework used in occupancy modeling can also be adapted to include or estimate taxa abundances [31].…”