Biology subjects

Slooten, E.

Publications and source records attributed to Slooten, E..

3 recordsLinked to original sources

bioRxiv2020

EXTINCTION RISK FROM HUMAN IMPACTS ON SMALL POPULATIONS OF MARINE MAMMALS

Population models used to set limits for whaling, fisheries bycatch and other human-caused mortality (HCM) usually focus on relatively large populations and do not include Allee effects (declines in population growth rate at small population sizes). These models are not suitable for managing small and endangered populations of marine mammals. We use a stochastic age-structured population model to investigate the effect of HCM on extinction risk. Compared to environmental variability and catastrophes, Allee effects had a strong influence on risk. Depending on the scenario, HCM (1) delayed the rate of population recovery (with no increased risk), (2) increased extinction risk because populations lingered at low levels, (3) increased extinction risk because the population was pushed below an Allee threshold, or (4) increased extinction risk over 100 years because the rate of extinction for a doomed population was accelerated. Population dynamics in small populations are poorly known for most marine mammals. Therefore, we recommend that managers consider the range of potential population dynamics for the species under consideration and make precautionary decisions on allowable levels of HCM. For critically depleted populations (e.g., small populations, well below historic levels) even low levels of HCM have the potential to substantially increase extinction risk.

ecology↗

bioRxiv2020

Updated population viability analysis, population trends and PBRs for Hector's and Maui dolphin

EXECUTIVE SUMMARYUpdated population viability analyses, incorporating the latest abundance and bycatch data indicate that: O_LIThe estimated population decline for Maui dolphin is 2% per year C_LIO_LIThere is a 68% probability that the population is continuing to decline C_LIO_LIAfter 30 years (6 more surveys) statistical power of detecting this rate of decline would be < 15% C_LIO_LIOnly very large declines (37%) and recovery (45%) would be detectable with 80% statistical power after 30 years (6 more surveys) C_LIO_LIThe level of conservation threat for Hectors dolphin remains high despite a recent, larger population estimate off the east coast of the South Island C_LIO_LIIncreased overlap between dolphins and fisheries, due to more extensive offshore distribution of dolphins off the South Island east coast, more than offsets the apparently higher population size C_LIO_LIThe Hectors dolphin population has declined 70% over the last 3 generations, exceeding the 50% threshold for Endangered C_LIO_LIPopulation declines are predicted to continue under current protection levels C_LIO_LIThe results of this research are consistent with: {bigcirc}NOAA proposal to list Hectors and Maui dolphins under the US Endangered Species Act {bigcirc}IWC recommendation to ban gillnets and trawling throughout Maui dolphin habitat {bigcirc}IUCN recommendation to ban gillnets and trawling throughout Hectors and Maui dolphin habitat C_LI

ecology↗

bioRxiv2020

Effectiveness of current protection for Maui dolphin

This paper describes changes to protected areas for Maui dolphin (Cephalorhynchus hectori mauii) implemented in 2012 and 2013, and estimates their effectiveness in reducing bycatch. An Expert Panel of New Zealand and international scientists, convened by the New Zealand government in 2012, estimated that five Maui dolphins were killed in fishing gear each year - one in trawl fisheries and four in gillnet fisheries. The estimated number of trawl mortalities is unchanged, as no additional protection from trawling has been implemented. The number of gillnet mortalities per year is estimated to have decreased to at best two per year. The International Whaling Commission has recommended that gillnet and trawl fisheries be banned in Maui dolphin habitat, reducing bycatch to as close as practicable to zero.

ecology↗