Springtime transport and retention of Calanus finmarchicus in Massachusetts and Cape Cod Bays, USA, and implications for right whale foraging

Abstract

The Massachusetts Bay (MB) and Cape Cod Bay (CCB) system is a unique coastal embayment, with CCB serving as a high-use feeding ground for endangered North Atlantic right whales Eubalaena glacialis during winter and early spring. We used a hydrodynamic model, observed Calanus finmarchicus (the preferred prey of right whales) abundance, and right whale sightings during 1997-2004 to examine the transport and retention of C. finmarchicus in MB-CCB and the implications for right whale activity. A particle-tracking program was embedded into the model to simulate the Lagrangian residual circulation, and the transport and retention of passive particles. The results indicate significant correlations in the inter-annual variability of coastal transport, circulation pattern, C. finmarchicus abundance, and right whale sightings in spring. In normal years (with prevailing northwesterly winds), the monthly mean distributions of particles and Lagrangian residual currents show a coherent pattern with 2 particle retention areas in central CCB and central MB, respectively. The CCB retention area closely matches the area of high probability of right whale occurrence and feeding activity, indicating that this is an area favorable to zooplankton aggregations. In other years (e.g. 2002), the coastal current is significantly reduced due to prevailing southwesterly winds, and the particle retention zone is shifted northward, coincident with low C. finmarchicus abundance and whale sightings in CCB. The study also suggests that the North Atlantic Oscillation may influence C. finmarchicus abundance and distributions, and hence, right whale feeding activity in CCB through surface winds affecting MB-CCB circulation, and hence, zooplankton distributions.

Model-based estimates of right whale habitat use in the Gulf of Maine

“…Pendleton et al (2009) (2006) found an association between right whales and zooplankton abundance, with variability in wind-driven currents playing a dominant role in determining plankton abundance. Particle tracking simulations support the assertion that circulation variability strongly influences copepod abundance and right whale feeding conditions, especially in coastal habitats (Jiang et al 2007). Kenney et al (2001) considered how the sensory mechanisms and foraging strategies used by right whales could change across spatial scales.…”

“…and Centropages typicus are important prey during this period (Mayo & Marx 1990, DeLorenzo Costa et al 2006). As C. finmarchicus abundance increases in early spring, increasing numbers of this species are transported into coastal regions like Cape Cod Bay (DeLorenzo Costa et al 2006, Jiang et al 2007), and C. finmarchicus becomes a larger component of the right whales' diet. Even though C. finmarchicus abundance increases in the spring in Cape Cod Bay, the abundance is even higher in deeper habitats (Meise & O'Reilly 1996) and right whale sightings in Cape Cod Bay begin to decline.…”

“…The number of right whales observed in Cape Cod Bay varies from year to year, and this variability has been linked to the abundance of C. finmarchicus (DeLorenzo Costa et al 2006, Jiang et al 2007) and the abundance of non-C. finmarchicus copepods, likely Centropages typicus and Pseudocalanus spp. ).…”

Phytoplankton Patterns in Massachusetts Bay—1992–2007

“…Calanus finmarchicus exhibited a precipitous drop from 2000 to 2001, followed by a sharp ascent in 2002 to maximum levels that were maintained through 2003-2004, and declined to slightly below mean levels during 2005-2007. The differing long-term zooplankton abundance patterns may reflect species-specific zooplankton responses to interannual variation in wind strength and direction as modulated by a large-scale driver of winter weather in this region (the North Atlantic Oscillation; Turner et al 2006, Jiang et al 2007b). …”

Phenological changes in North Atlantic right whale habitat use in Massachusetts Bay

“…However, numerous prior studies suggest that much of the variation in right whale habitat use over timescales of weeks to years in the Gulf of Maine and adjacent regions is driven by the varying distribution of the extremely dense patches of copepod prey that right whales apparently require for energetically profitable feeding (Baumgartner, Cole, Clapham, & Mate, 2003;Baumgartner et al, 2007;Davies et al, 2015;Jiang et al, 2007;Mayo & Marx, 1990;Patrician & Kenney, 2010;Pendleton et al, 2009Pendleton et al, , 2012Pershing et al, 2009). In some studies, physical oceanographic features such as bathymetry, SST, SST gradient, bottom mixed layer depth, salinity profiles, and circulation patterns have been found to be correlated with right whale habitat use, but the influences of these physical factors on whale distribution are probably indirect, via their effects on prey concentration Jiang et al, 2007;Keller et al, 2006;Pendleton et al, 2009Pendleton et al, , 2012Pershing et al, 2009). Other environmental parameters, such as chlorophyll concentration, weakly correlate with right whale calving rates (Hlista, Sosik, Traykovski, Kenney, & Moore, 2009) and habitat suitability (Pendleton et al, 2012).…”