The relationship between summer aggregation of fin whales and satellite-derived environmental conditions in the northwestern Mediterranean Sea

The development of synoptic tools is required to derive the potential habitat of fin whales Balaenoptera physalus on a large-scale basis in the Mediterranean Sea, as the species has a largely unknown distribution and is at high risk of ship strike. We propose a foraging habitat model for fin whales in the western Mediterranean Sea relying on species ecology for the choice of predictors. The selected environmental variables are direct predictors and resource predictors available at daily and basin scales. Feeding habitat was determined mainly from the simultaneous occurrence of large oceanic fronts of satellite-derived sea-surface chlorophyll content (chl a) and temperature (SST). A specific range of surface chl a content (0.11 to 0.39 mg m −3) and a minimum water depth (92 m) were also identified to be important regional criteria. Daily maps were calibrated and evaluated against independent sets of fin whale sightings (presence data only). Specific chl a fronts represented the main predictor of feeding environment; therefore, derived habitat is a potential, rather than effective, habitat, but is functionally linked to a proxy of its resource (chl a production of fronts). The model performs well, with 80% of the presence data < 9.7 km from the predicted potential habitat. The computed monthly, seasonal and annual maps of potential feeding habitat from 2000 to 2010 correlate, for the most part, with current knowledge on fin whale ecology. Overall, fin whale potential habitat occurs frequently during summer in dynamic areas of the general circulation, and is substantially more spread over the basin in winter. However, the results also displayed high year-to-year variations (40 to 50%), which are essential to consider when assessing migration patterns and recommending protection and conservation measures.KEY WORDS: Balaenoptera physalus · Potential habitat · Feeding · Mediterranean Sea · Satellite data · Fronts · Chlorophyll a · Environmental niche model Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 464: [289][290][291][292][293][294][295][296][297][298][299][300][301][302][303][304][305][306] 2012 eral anthropogenic threats affect the Mediterranean fin whale population, with vessel strikes being one of the main causes of human-induced mortality (Panigada et al. 2006). The risk of a vessel strike is particularly severe in areas of heavy maritime traffic, such as the PELAGOS Sanctuary (ACCOBAMS 2006, David et al. 2011, where fin whales tend to concentrate in high numbers during the summer months (Gannier 1997, 2002, Notarbartolo di Sciara et al. 2003, Panigada et al. 2005, Würtz 2010. The PELAGOS Sanctuary is the first International Marine Protected Area (MPA) created in the high seas (Hoyt 2005) that aims at integrating human activities with cetacean conservation (Notarbartolo di Sciara 2007). While shipping noise is one source of disturbance, seismic airguns used for oil and gas exploration can also deter fin whales from feeding or breeding grounds (Cas...

Section: Selection Of Methods and Predictorsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Potential feeding habitat of fin whales in the western Mediterranean Sea: an environmental niche model

Druon¹,

Panigada²,

David³

et al. 2012

“…Satellite-derived SST data have become a widely used tool for monitoring changes in ocean temperature driven by climate change and have been incorporated into a myriad of biological models and studies (e.g. Littaye et al 2004, Zainuddin et al 2006, Muhling et al 2008. Temperature is a key factor controlling the distribution of species and physiological processes (Schils & Wilson 2006, O'Connor et al 2007, Byrne et al 2009, Staehr & Wernberg 2009, and easily accessible temperature data for the global ocean has facilitated considerable progress in our understanding of broad-scale biological patterns.…”

Section: Introductionmentioning

confidence: 99%

Satellite-derived SST data as a proxy for water temperature in nearshore benthic ecology

Smale¹,

Wernberg²

2009

136

133

Satellite-derived sea surface temperatures (SSTs) are increasingly being used as a proxy for water temperature in nearshore marine ecology, but there have been very few evaluations of how accurately SSTs reflect actual temperatures experienced by subtidal organisms. Here, we describe the benthic temperature climatology of 4 coastal locations along a ~1000 km latitudinal gradient in ocean temperature in Western Australia (WA), and compare temperature records from in situ loggers at 10 to 12 m depth with records from 2 independent satellite-derived SST datasets over 2 years. Satellite-derived SSTs were significantly correlated with in situ logger data at all locations, which demonstrate their overall ability to detect general patterns of ecological importance. However, SSTs were also significantly different from benthic water temperatures (usually 1 to 2°C higher), and they did not adequately detect ecologically important small-scale variability or provide reliable information on temperature extremes. Furthermore, rank orders of the study locations differed between the methodologies, especially in winter. We emphasize the need to carefully consider whether the accuracy and resolution of satellite-derived SSTs are appropriate for the specific ecological hypothesis being tested in nearshore subtidal habitats, and advocate the use of in situ loggers otherwise. We also highlight the suitability of the WA coastline for experimental work on the effects of temperature (and synergistic factors) on marine organisms. KEY WORDS: Benthic climatology · Satellite-derived SST · Temperature gradient · Shallow water habitats Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 387: [27][28][29][30][31][32][33][34][35][36][37] 2009 ever, this measurement is derived from the top 'skin' of seawater (~0.01 mm thick) and may not be representative of seawater temperature further down in the water column ('bulk' temperature). The relationship between 'skin' and 'bulk' temperature is strongly influenced by sea state, weather conditions and local oceanography, and has been the focus of many ground-truthing studies (Barton & Pearce 2006. It is clear that, under certain conditions, SST values may be representative of water temperatures to depths of a few meters in the open ocean (Katsaros 2003). Such observations may have prompted the use of satellite-derived SSTs in shallow-water ecological studies. However, in shallow coastal benthic habitats, factors such as tides, waves, water clarity and the thermal properties of the substratum, may influence temperature profiles and possibly reduce the correspondence between SSTs and the temperatures experienced by organisms living near the bottom. Given the severity of likely impacts, there is an increasing need to understand how organisms would respond to the current rate of global change, including ocean warming, and such an understanding is only possible if coupled with accurate environmental data. Here, we compare temperatures measured in sit...

“…Laidre et al 2008), it may be more pragmatic to investigate such effects on a studyby-study basis, by comparing the strength of relationships between spatial usage and biophysical covariates lagged at a range of plausible distances (e.g. Littaye et al 2004, Croll et al 2005. Despite their limitations, remotely sensed environmental data can describe habitats in a biologically meaningful way (Table 2), especially when multiple variables are used synergistically to derive other descriptors of habitat, such as the rate of primary production (Behrenfeld & Falkowski 1997), mixed layer depth (Zawada et al 2005), and measures of mesoscale activity (e.g.…”

Section: Measuring the Marine Environmentmentioning

confidence: 99%

Quantifying habitat use and preferences of pelagic seabirds using individual movement data: a review

Wakefield¹,

Phillips²,

Matthiopoulos³

2009

169

198

Colonial seabirds are relatively easy to observe, count, measure and manipulate, and consequently have long been used as models for testing ecological hypotheses. A combination of animal tracking and satellite imagery has the potential to greatly inform such efforts, by allowing seabird -environment interactions to be observed remotely. We review how this can be achieved by applying innovative statistical techniques to quantify habitat use and preferences. Seabird movements are now observable at scales of meters using GPS loggers, and up to several years using lightbased geolocation, while satellite remote sensing systems, at resolutions of km, are capable of characterizing the millions of km 2 of habitat that are accessible to seabirds. Physical forcing and biological processes result in a hierarchical, patchy distribution of prey. Hence, analyses of seabird movements should be conducted at appropriate scales. Variation in habitat accessibility should also be considered: this declines with distance from the colony during the breeding season, when seabirds are central place foragers, and may be limited in the nonbreeding period by migration corridors that are defined by wind patterns. Intraspecific competition can further modify spatial usage, leading to spatial segregation of birds foraging from different colonies. We recommend that spatial usage be modeled as a function of habitat preference, accessibility and, potentially, competition. At the population level, this is currently best achieved using an empirical approach (e.g. using mixed-effects generalized additive models). At the individual level, more mechanistic models (e.g. state-space models) are more appropriate and have the advantage of modeling location errors explicitly.