Estimating the effects of stressors on the health, survival and reproduction of a critically endangered, long-lived species

Funding: Office of Naval Research (Grant Number(s): N000142012697, N000142112096); Strategic Environmental Research and Development Program (Grant Number(s): RC20-1097, RC20-7188, RC21-3091).Quantifying the cumulative effects of stressors on individuals and populations can inform the development of effective management and conservation strategies. We developed a Bayesian state–space model to assess the effects of multiple stressors on individual survival and reproduction. In the model, stressor effects on vital rates are mediated by changes in underlying health, allowing for the comparison of effect sizes while accounting for intrinsic factors that might affect an individual's vulnerability and resilience. We applied the model to a 50-year dataset of sightings, calving events and stressor exposure of critically endangered North Atlantic right whales Eubalaena glacialis. The viability of this population is threatened by a complex set of stressors, including vessel strikes, entanglement in fishing gear and fluctuating prey availability. We estimated that blunt and deep vessel strike injuries and severe entanglement injuries had the largest effect on the health of exposed individuals, reinforcing the urgent need for mitigation measures. Prey abundance had a smaller but protracted effect on health across individuals, and estimated long-term trends in survival and reproduction followed the trend of the prey index, highlighting that long-term ecosystem-based management strategies are also required. Our approach can be applied to quantify the effects of multiple stressors on any long-lived species where suitable indicators of health and long-term monitoring data are available.Publisher PDFPeer reviewe

Remote climate forcing of decadal-scale regime shifts in Northwest Atlantic shelf ecosystems

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2013. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Association for the Sciences of Limnology and Oceanography, doi:10.4319/lo.2013.58.3.0803.Decadal-scale regime shifts in Northwest Atlantic shelf ecosystems can be remotely forced by climate-associated atmosphere–ocean interactions in the North Atlantic and Arctic Ocean Basins. This remote climate forcing is mediated primarily by basin- and hemispheric-scale changes in ocean circulation. We review and synthesize results from process-oriented field studies and retrospective analyses of time-series data to document the linkages between climate, ocean circulation, and ecosystem dynamics. Bottom-up forcing associated with climate plays a prominent role in the dynamics of these ecosystems, comparable in importance to that of top-down forcing associated with commercial fishing. A broad perspective, one encompassing the effects of basin- and hemispheric-scale climate processes on marine ecosystems, will be critical to the sustainable management of marine living resources in the Northwest Atlantic.Funding for this research was provided by the National Science Foundation as part of the Regional and Pan-Regional Synthesis Phases of the U.S. Global Ocean Ecosystem (GLOBEC) Program

IMPACTS OF CLIMATE-ASSOCIATED CHANGES IN PREY AVAILABILITY ON NORTH ATLANTIC RIGHT WHALE POPULATION DYNAMICS

Today’s oceans are undergoing rapid and unprecedented changes resulting from anthropogenic impacts. The North Atlantic right whale, one of the most endangered baleen whales with just over 500 animals remaining in the species, is one example of a species at risk resulting from human influence. Modern right whale research is focused on elevated mortality rates due to vessel collisions and fishing gear entanglement. Although understudied, depressed calving rates also contribute significantly to slow growth. Here we analyze the effect of climate-driven fluctuations in prey abundance on right whale reproductive dynamics since 1980. Calanus finmarchicus, the lipid-rich copepod that right whales prey on, were anomalously abundant in the 1980s and 2000s, while concentrations were low in the 1990s. These fluctuations in copepod abundance were driven remotely by freshwater pulses from the Arctic Ocean, and by changes in advective supply to the Gulf of Maine related to North Atlantic circulation patterns. Synchronized with the low prey regime, right whale calf production in the 1990s was depressed relative to the surrounding decades. In a series of matrix population models, physical variables tied to basin-scale oceanographic mechanisms, climate indices and Continuous Plankton Recorder-derived C. finmarchicus abundance anomalies were tested in the prediction of right whale calf births over the time series 1980-2007. While several lagged physical variables and the annual C. finmarchicus anomaly outcompeted the prey-independent calf prediction model, the best reproduction model was driven by a combination of bimonthly anomalies in sub-regions spanning the southern Gulf of Maine. The objectively-selected regions and seasons of prey anomalies driving the best reproduction model correspond well with known right whale feeding and breeding habits

Climate-Associated Regime Shifts Drive Decadal-Scale Variability in Recovery of North Atlantic Right Whale Population

Despite an elevated mortality rate from lethal interactions with humans, the North Atlantic right whale population has continued to grow during the first decade of the new millennium. This unexpected population growth is the result of a 128% increase in female-specific reproduction relative to the 1990s. Here, we demonstrate that the recent increase in annual right whale calf production is linked to a dramatic increase in the abundance of its major prey, the copepod species Calanus finmarchicus, in the Gulf of Maine. The resurgence of C. finmarchicus was associated with a regime shift remotely forced by climatic changes in the Arctic. We conclude that decadal-scale variability in right whale reproduction may be largely driven by fluctuations in prey availability linked to climate-associated ecosystem regime shifts