Absolute probability estimates of lethal vessel strikes to North Atlantic right whales in Roseway Basin, Scotian Shelf

Author Posting. © Ecological Society of America, 2012. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 22 (2012): 2021–2033, doi:10.1890/11-1841.1.Vessel strikes are the primary source of known mortality for the endangered North Atlantic right whale (Eubalaena glacialis). Multi-institutional efforts to reduce mortality associated with vessel strikes include vessel-routing amendments such as the International Maritime Organization voluntary “area to be avoided” (ATBA) in the Roseway Basin right whale feeding habitat on the southwestern Scotian Shelf. Though relative probabilities of lethal vessel strikes have been estimated and published, absolute probabilities remain unknown. We used a modeling approach to determine the regional effect of the ATBA, by estimating reductions in the expected number of lethal vessel strikes. This analysis differs from others in that it explicitly includes a spatiotemporal analysis of real-time transits of vessels through a population of simulated, swimming right whales. Combining automatic identification system (AIS) vessel navigation data and an observationally based whale movement model allowed us to determine the spatial and temporal intersection of vessels and whales, from which various probability estimates of lethal vessel strikes are derived. We estimate one lethal vessel strike every 0.775–2.07 years prior to ATBA implementation, consistent with and more constrained than previous estimates of every 2–16 years. Following implementation, a lethal vessel strike is expected every 41 years. When whale abundance is held constant across years, we estimate that voluntary vessel compliance with the ATBA results in an 82% reduction in the per capita rate of lethal strikes; very similar to a previously published estimate of 82% reduction in the relative risk of a lethal vessel strike. The models we developed can inform decision-making and policy design, based on their ability to provide absolute, population-corrected, time-varying estimates of lethal vessel strikes, and they are easily transported to other regions and situations.This research was supported by the Environment Canada Habitat Stewardship Programme, the Canadian Whale Institute, and R. K. Smedbol (St. Andrews Biological Station)

Simulated and experimental estimates of hydrodynamic drag from bioâ logging tags

Drag force acting on swimming marine mammals is difficult to measure directly. Researchers often use simple modeling and kinematic measurements from animals, or computational fluid dynamics (CFD) simulations to estimate drag. However, studies that compare these methods are lacking. Here, computational simulation and physical experiments were used to estimate drag forces on gliding bottlenose dolphins (Tursiops truncatus). To facilitate comparison, variable drag loading (noâ tag, tag, tagâ +â 4, tagâ +â 8) was used to increase force in both simulations and experiments. During the experiments, two dolphins were trained to perform controlled glides with variable loading. CFD simulations of dolphin/tag geometry in steady flow (1â 6â m/s) were used to model drag forces. We expect both techniques will capture relative changes created by experimental conditions, but absolute forces predicted by the methods will differ. CFD estimates were within a calculated 90% confidence interval of the experimental results for all but the tag condition. Relative drag increase predicted by the simulation vs. experiment, respectively, differed by between 21% and 31%: tag, 4% vs. 33%; tagâ +â 4, 47% vs. 68%; and tagâ +â 8, 108% vs. 77%. The results from this work provide a direct comparison of computational and experimental estimates of drag, and provide a framework to quantify uncertainty.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152630/1/mms12627.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152630/2/mms12627_am.pd

Swimming Energy Economy in Bottlenose Dolphins Under Variable Drag Loading

Instrumenting animals with tags contributes additional resistive forces (weight, buoyancy, lift, and drag) that may result in increased energetic costs; however, additional metabolic expense can be moderated by adjusting behavior to maintain power output. We sought to increase hydrodynamic drag for near-surface swimming bottlenose dolphins, to investigate the metabolic effect of instrumentation. In this experiment, we investigate whether (1) metabolic rate increases systematically with hydrodynamic drag loading from tags of different sizes or (2) whether tagged individuals modulate speed, swimming distance, and/or fluking motions under increased drag loading. We detected no significant difference in oxygen consumption rates when four male dolphins performed a repeated swimming task, but measured swimming speeds that were 34% (>1 m s-1) slower in the highest drag condition. To further investigate this observed response, we incrementally decreased and then increased drag in six loading conditions. When drag was reduced, dolphins increased swimming speed (+1.4 m s-1; +45%) and fluking frequency (+0.28 Hz; +16%). As drag was increased, swimming speed (-0.96 m s-1; -23%) and fluking frequency (-14 Hz; 7%) decreased again. Results from computational fluid dynamics simulations indicate that the experimentally observed changes in swimming speed would have maintained the level of external drag forces experienced by the animals. Together, these results indicate that dolphins may adjust swimming speed to modulate the drag force opposing their motion during swimming, adapting their behavior to maintain a level of energy economy during locomotion.Summary Statement: Biologging and tracking tags add drag to study subjects. When wearing tags of different sizes, dolphins changed their swimming paths, speed, and movements to modulate power output and energy consumption

Turbulent flow reduces oxygen consumption in the labriform swimming shiner perch, Cymatogaster aggregata

Fish swimming energetics are often measured in laboratory environments which attempt to minimize turbulence, though turbulent flows are common in the natural environment. To test whether the swimming energetics and kinematics of shiner perch Cymatogaster aggregata (a labriform swimmer) were affected by turbulence, two flow conditions were constructed in a swim-tunnel respirometer. A low-turbulence flow was created using a common swim-tunnel respirometry setup with a flow straightener and fine-mesh grid to minimize velocity fluctuations. A high-turbulence flow condition was created by allowing large velocity fluctuations to persist without a flow straightener or fine grid. The two conditions were tested with Particle Image Velocimetry to confirm significantly different turbulence properties throughout a range of mean flow speeds. Oxygen consumption rates of the swimming fish increased with swimming speeds and pectoral fin beat frequencies in both flow conditions. Higher turbulence also caused a greater positional variability in swimming individuals (vs. low-turbulence flow) at medium and high speeds. Surprisingly, fish used less oxygen in high turbulence compared to low-turbulence flow at medium and high swimming speeds. Simultaneous measurements of swimming kinematics indicated that these reductions in oxygen consumption could not be explained by specific known flow-adaptive behaviours such as Kármán-gaiting or entraining. Therefore, fish in high-turbulence flow may take advantage of the high variability in turbulent energy through time. These results suggest that swimming behavior and energetics measured in the lab in straightened flow, typical of standard swimming respirometers, might differ from that of more turbulent, semi-natural flow conditions.PostprintPeer reviewe

Erratum to “Vessel strikes to large whales before and after the 2008 Ship Strike Rule”

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Conservation Letters 9 (2016): 236, doi:10.1111/conl.12273

Effects and added drag on cetaceans : fishing gear entanglement and external tag

Thesis: Ph. D., Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Biology; and the Woods Hole Oceanographic Institution), 2017.Cataloged from PDF version of thesis.Includes bibliographical references (pages 283-314).Animal movement is motivated in part by energetic constraints, where fitness is maximized by minimizing energy consumption. The energetic cost of movement depends on the resistive forces acting on an animal; changes in this force balance can occur naturally or unnaturally. Fishing gear that entangles large whales adds drag, often altering energy balance to the point of terminal emaciation. An analog to this is drag from tags attached to cetaceans for research and monitoring. This thesis quantifies the effects of drag loading from these two scenarios on fine-scale movements, behaviors and energy consumption. I measured drag forces on fishing gear that entangled endangered North Atlantic right whales and combined these measurements with theoretical estimates of drag on whales' bodies. Entanglement in fishing gear increased drag forces by up to 3 fold. Bio-logging tags deployed on two entangled right whales recorded changes in the diving and fine-scale movement patterns of these whales in response to relative changes in drag and buoyancy from fishing gear and through disentanglement: some swimming patterns were consistently modulated in response. Disentanglement significantly altered dive behavior, and can affect thrust production. Changes in the force balance and swimming behaviors have implications for the survival of chronically entangled whales. I developed two bioenergetics approaches to estimate that chronic, lethal entanglements cost approximately the same amount as the cost of pregnancy and supporting a calf to near-weaning. I then developed a method to estimate drag, energy burden and survival of an entangled whale at detection. This application is essential for disentanglement response and protected species management. Experiments with tagged bottlenose dolphins suggest similar responses to added drag: I determined that instrumented animals slow down to avoid additional energetic costs associated with drag from small bio-logging tags, and incrementally decrease swim speed as drag increases. Metabolic impacts are measurable when speed is constrained. I measured the drag forces on these tags and developed guidelines depending on the relative size of instruments to study-species. Together, these studies quantify the magnitude of added drag in complementary systems, and demonstrate how animals alter their movement to navigate changes in their energy landscape associated with increased drag.by Julie M. van der Hoop.Ph. D

The Painful Side of Trap and Fixed Net Fisheries: Chronic Entanglement of Large Whales

Concern over the well-being of marine mammals at sea has focused on intentional harvests, both in terms of individual welfare and population sustainability. Unintentional mortalities from fishing gear entanglement are primarily seen as a risk to population viability. Additionally, larger whales breaking free of, and subsequently carrying, fixed trap and net gear are subject to a very slow demise, averaging 6 months in the case of the North Atlantic right whale (Eubalaena glacialis). Chronic cases can involve impaired foraging, increased drag, infection, hemorrhage, and severe tissue damage. The individual suffering of these cases appears to be extreme. Thus management measures should go beyond legally mandated conservation measures to include avoidance of such scenarios. Seafood consumers could succeed, where laws have failed, to demand fishing practices that do not kill whales in this manner. The effective absence of such demands would seem to reflect the cryptic nature of these cases to most consumers

Vessel strikes to large whales before and after the 2008 Ship Strike Rule

© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Conservation Letters 8 (2015): 24-32, doi:10.1111/conl.12105.To determine effectiveness of Seasonal Management Areas (SMAs), introduced in 2008 on the U.S. East Coast to reduce lethal vessel strikes to North Atlantic right whales, we analyzed observed large whale mortality events from 1990–2012 in the geographic region of the “Ship Strike Rule” to identify changes in frequency, spatial distribution, and spatiotemporal interaction since implementation. Though not directly coincident with SMA implementation, right whale vessel-strike mortalities significantly declined from 2.0 (2000–2006) to 0.33 per year (2007–2012). Large whale vessel-strike mortalities have decreased inside active SMAs, and increased outside inactive SMAs. We detected no significant spatiotemporal interaction in the 4-year pre- or post-Rule periods, although a longer time series is needed to detect these changes. As designed, SMAs encompass only 36% of historical right whale vessel-strike mortalities, and 32% are outside managed space but within managed timeframes. We suggest increasing spatial coverage to improve the Rule's effectiveness.North Pond Foundation; M. S. Worthington Foundation; Natural Sciences and Engineering Research Council of Canada (NSERC

Appendix A. Estimation of right whale deaths by vessel strike.

Estimation of right whale deaths by vessel strike