Study of baleen whales’ ecology and interaction with maritime traffic activities to support management of a complex socio-ecological system
Management of the marine environment for multiple usages has become increasingly complex. The creation of Marine Protected Areas (MPAs) has been pointed out as a successful strategy for combining conservation with other uses. However, to attain conservation goals, a well-defined management plan and a robust monitoring program need to be set. In 1998, the Saguenay St. Lawrence Marine Park (SSLMP) was decreed to protect important ecosystems of the St. Lawrence River Estuary. A growing whale watching industry was already established in the area which is also crossed by an important shipping lane. Thirteen marine mammal species occur in the area, among them, four baleen species, which are the focus of the present work: minke whales (Balaenoptera acutorostrata), fin whales (Balaenoptera physalus), humpback whales (Megaptera novaeangliae) and the blue whales (Balaenoptera musculus). Whales’ protection in this area of intensive marine traffic is of concern due to a high collision probability and induced behavioral and physiological changes. Before addressing the effects of the marine traffic, some basic questions needed to be answered: How many baleen whales use the area? Where are their core areas? To answer that, line-transect distance-sampling data collected over four years (2006-2009) were used to estimate density and abundance and to build a spatial density model (SDM). The most abundant species were minke (45, 95% CI=34-59) and fin whales (24, 95% CI=18-34), followed by blue (3, 95% CI=2-5) and humpback whales (2, 95% CI=1-4). Generalized additive models were used to model each species count as a function of space and environmental variables. The SDM allowed the identification of each species core area within the marine portion of the SSLMP, and corroborated the abundance estimates derived from design-based methods. In addition, it corroborated the relevance of the proposed St. Lawrence Estuary Marine Protected (SLEMPA) Area to the conservation of essential habitats of the endangered blue whale. An extrapolation exercise was performed to predict blue whales’ habitats outside the surveyed area. Despite its exploratory nature, the results showed a good match with independent data sets and in the lack of better information could guide the discussion of management measures to enhance species’ protection. Next, Geographic Information System capabilities were used to verify the degree of overlap between the navigation corridor and the resulting SDM of each species and the extrapolation model. The analysis highlighted areas of important co-occurrence of whales and ships, corroborated the adequacy of recently proposed management measures and resulted in a recommendation of adjustment to the current shipping lane in order to decrease collision risk. Finally, the overlap with the whale watching industry was characterized with data from a land-based survey conducted from 2008 to 2010. Although all baleen whale species were tracked, here only results of blue and humpback whales were presented. For blue whales, data from 14 hours of observation were analyzed. Whales were exposed to boats, mainly commercial zodiacs, in 74% of their surface intervals (SI). Continuous exposure ranged from 2 to 19 SI and the mean number of boats within a 1 km radius was 2.3 (±2.7, max=14). A complete lack of compliance with the current whale watching regulations was observed. Additionally, individual blow rate variance was correlated with percentage of exposure to boats (0.73, p<0.05). Although humpback whales do not have a critical conservation status, their intrinsic behaviour makes them a major target to the industry. A total of 50.4 hours of humpback whale observation was analysed. Whales were exposed to boats, mainly commercial zodiacs, during 78.5% of the observation time. The mean number of boats within a 1 km radius was 1.9 (±2.3, max=22). The cumulative exposure to whale watching can have long-term consequences for whales. Law enforcement and measures to raise awareness and compliance to current regulations are urgently needed. Suggestions to improve the current regulation were provided. The present work presents the first abundance estimates for the study area, refines the available information on baleen whales core areas, provides support to the establishment of an adequate zoning plan within the SSLMP and stresses the relevance of the SLEMPA. In addition it provides an in depth overview of the marine traffic issue and provides valuable information to support management of this complex socio-ecological system.
Baleen whales Abundance estimates Spatial density model Marine traffic Whale watching St. Lawrence Management Marine protected areas Gestion