A proposal to define vulnerability of cetacean areas to human development: variables and analysis procedures applied to the Gulf of California

Abstract

ABSTRACT1. Understanding spatial interactions between specific sources of anthropogenic impact on cetaceans and the ecological conditions intrinsic to these mammals, has several applications for conservation and management. Here cetacean habitats are classified into vulnerability levels by combining human development metrics and cetacean characteristics, allowing areas identified as more vulnerable to be given management priority.2. Ten bio-physical and anthropogenic factors were identified as key shapers of cetacean habitats and, using the Gulf of California as a case study, 18 variables were defined to measure those factors. Principal component analysis (PCA) and GIS were used to distill the relationships across all variables, in order to obtain a vulnerability index. Aggregates of variables were also investigated to map the spatial distribution of anthropogenic impacts and cetacean characteristics (species richness, relative abundance of encounter, residence condition, diet specificity and threat status). For this latter purpose, separate indices representing five 'categories' (pollution from land sources, urban development, potential for accidents, resource depletion and fragility of cetacean areas) and three 'vulnerability components' (risk of hazards, intrinsic resilience and damage) were calculated.3. The methodology clearly differentiated the study area according to levels for each 'category' and 'vulnerability component', as well as to levels of vulnerability of cetacean areas in relation to human activities; and identified those variables with the greatest contributions, without recourse to the subjective criteria common in other approaches. The analyses were conducted using environmental units generated by the Marine Ecological Zoning Plan for the Gulf of California (OEMGC, by its Spanish acronym) which tied model outputs to this planning framework. The variables selected were easily obtainable through governmental and research institutions which make them suitable for adaptive management purposes.

Fin whale movements in the Gulf of California, Mexico, from satellite telemetry

“…The intensity and spatial extent of these threats to marine mammals in the GoC is unclear, but sightings of entangled cetaceans or individuals with ship strike marks have been increasing in recent years in Mexico [91]. The results obtained in this study will help better identify areas where interactions between fin whales and threats need to be monitored and evaluated to make better decisions regarding development plans and to manage responses to human activities [93]. Also, we suggest a greater sampling effort during the warm season in the north of the GoC to gain a better understanding of fin whale movements during this time for which data remain scarce.…”

Ecological guidelines for designing networks of marine reserves in the unique biophysical environment of the Gulf of California

“…Where some species move long distances (e.g. large sharks and cetaceans), reserves may need to be combined with other management approaches, such as restrictions on the use of nets or boats (Cubero-Pardo et al 2011).…”

“…There have also been several regional assessments that provide overviews of local threats to marine ecosystems and how they vary throughout the GOC (Cubero-Pardo et al 2011;Alvarez-Romero et al 2013;Morzaria-Luna et al 2014). For example, HaroMartinez et al (2000) used a multicriteria, processdriven approach to calculate the potential spatial dispersion of environmental pressure (or threats) derived by human activities.…”

Influence of Life-History Parameters on Persistent Organic Pollutant Concentrations in Blubber of Eastern North Pacific Gray Whales (Eschrichtius robustus)

“…The presence of persistent organic pollutants (POPs) in the marine environment is of global concern for marine mammal health and habitat quality. , Marine mammals are particularly susceptible to bioaccumulating these lipophilic contaminants in their blubber and are at risk of associated effects including developmental dysfunction, endocrine system disruption, reproductive failure, and immunosuppression. − Due to their toxicity and environmental persistence, the production and use of POPs, such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), chlordanes (CHLs), hexachlorocyclohexanes (HCHs), and polybrominated diphenyl ethers (PBDEs), have been prohibited or greatly limited since the 2001 Stockholm Convention on Persistent Organic Pollutants and its subsequent addendums. Despite this ban, POPs remain a threat to wildlife on account of their environmental persistence, long-range transport, bioaccumulation, and continued production and use in nonsignatory countries.…”