Applications of GIS to Entanglement Science: An annotated bibliography

Prepared for Introduction to Geographic Information Science (GEOG560) at Oregon State University

Rachel Kaplan, PhD student, Oregon State University College of Earth, Ocean, and Atmospheric Sciences and Department of Fisheries, Wildlife, and Conservation Sciences, Geospatial Ecology of Marine Megafauna Lab

The entanglement of whales and other marine mammals in fishing gear is a complex problem that affects both natural systems and the human systems that rely upon them. In addition, entanglement events are difficult to observe and address. Diverse scientific and management efforts are aimed at improving our ability to mitigate entanglement risk to marine mammals, understand the impacts of these events, and predict when and where entanglements may occur. Geographic Information Systems (GIS) offers an important toolkit that can support these aims.

This webpage collects research papers and other resources on the following themes: 1) applications of GIS to entanglement science, and 2) GIS research that illuminates ecosystems and supports entanglement mitigation via modeling and management efforts.


Remote observation: satellite data, tags, and photo identification

Bamford, C. C. G., et al. (2020). A comparison of baleen whale density estimates derived from overlapping satellite imagery and a shipborne survey. Sci Rep 10(1): 12985.

The gold standard for baleen whale abundance and distribution data collection are aerial and shipboard surveys. The data obtained through these methods inform efforts to mitigate entanglement risk as well as research on whale life history, population health, and more. However, conducting these surveys is costly, logistically complex, and potentially dangerous. In this study, Bamford et al. explore the use of Very-High-Resolution (VHR) satellite as an alternative method for collecting whale abundance and distribution data. They authors compare whale density results derived from observations collected simultaneously by both a shipboard transect survey and a VHR satellite observing system in the Gerlache Strait, a remote region in the Western Antarctic Peninsula. They find that, when satellite data are corrected for surface availability and weather conditions, whale densities obtained from both methods are within an order of magnitude of one another. The authors conclude that satellite remote sensing has the potential to be used as a safer, non-invasive way of studying whale distribution and abundance in remote locations.

Ramp, Christian et al. Up in the air: drone images reveal underestimation of entanglement rates in large rorqual whales. Endangered Species Research 44 (2021): 33-44.

Though entanglement in fishing gear is recognized as one of the biggest threats to cetaceans worldwide, these events may be difficult to detect due to a lack of human observers in the area. Photo-identification images have been used to identify entanglement scars on individual whales, allowing researchers to derive species-specific entanglement rates, but these images fail to show regions of the body where scarring often occurs. Ramp et al. use geo-located drone imagery from the Gulf of St. Lawrence to recalculate species-specific entanglement rates, based on images that show a greater proportion of an individual whale’s body. The authors conclude that entanglement rates for fin, blue, and humpback whales have been underestimated through traditional photo-identification images, and that aerial surveys more accurately quantify entanglement rates in these species.

Tackaberry, J., et al. (2022). Low Resighting Rate of Entangled Humpback Whales Within the California, Oregon, and Washington Region Based on Photo-Identification and Long-Term Life History Data. Frontiers in Marine Science 8.

Entanglement is a leading source of human-caused mortality in whales, but it is difficult to detect these events and to monitor the outcome of whales that suffer from them. Tackaberry et al. use a library of geo-referenced photo identification images from California, Washington, and Oregon. They identify humpback whales entangled between 1982-2017 to analyze sighting histories of individuals before and after entanglement. The authors find that entangled whales were resighted less often than control groups, suggesting behavioral changes due to injury or mortality. They also clarify the mortality risk that entanglement poses for whales in different life stages and compare their findings to the National Oceanic and Atmospheric Association’s (NOAA) Serious Injury and Mortality Index, which seeks to quantify the impact of entanglement and other injuries to whales.

Rohner, C. A., et al. (2018). Satellite tagging highlights the importance of productive Mozambican coastal waters to the ecology and conservation of whale sharks. PeerJ 6: e4161.

Aerial surveys provide the opportunity to track migratory species with wide distributions, like the whale shark. Rohner et al. used aerial surveys to identify high densities and one hotspot of whale shark occurrence off the southern Mozambique coast, and then tagged 15 juveniles with SPOT5 satellite tags in order to track their movements away from the hotspot. The authors used the resulting geo-located tracklines to study whale shark habitat preference, and learned that the animals spend significantly more time in cooler, shallower, productive coastal waters than suggested by random modeling. To learn more about potential entanglement risk near the whale shark habitat hotspot, the researchers also mapped gill net distributions off the coast through two aerial surveys and over a thousand boat-based surveys. The spatial overlap of the whale shark occurrence and gill net fishing areas revealed that the increase in drifting gill net use likely poses a significant entanglement risk to regional populations of whale sharks.

Basran, Charla J. et al. First estimates of entanglement rate of humpback whales Megaptera novaeangliae observed in coastal Icelandic waters. Endangered Species Research (2019): n. pag.

Entanglement in fishing gear is common for large whales, yet it is difficult to calculate population-level rates of entanglement. In this study, Basran et al. use geo-located photo-identification images to identify entanglement scars on humpback whales in three areas of coastal Iceland. They found that, at minimum, 24.8% of individuals studied had a prior history of entanglement when they were first spotted, and at maximum, 50.1% had a history of entanglement. For some individuals, spatial and temporal dimensions of the photographic evidence suggested that entanglement events were occurring locally, providing potentially valuable information for managers seeking to lower entanglement risk to whales.

Using GIS to Detangle Ecological Relationships

Benoit-Bird, K. J. and G. L. Lawson (2016). Ecological Insights from Pelagic Habitats Acquired Using Active Acoustic Techniques. Ann Rev Mar Sci 8: 463-490.

Marine pelagic systems are remote, deep, and difficult to study. Using active acoustic techniques can offer researchers a unique perspective on these ecosystems and allow for integration with complementary sampling platforms and multiple data streams, at multiple spatial and temporal scales. Benoit-Bird and Lawson overview insights that can be gained from active acoustic techniques, which involve producing a pulse of sound and listening to the echoes that are backscattered by objects in the water column (e.g. animals or the seafloor). These techniques can be used to survey broad swathes of ocean or monitor how one area changes through time, even allowing researchers to remotely detect whale lungs or entire bodies.

Santora, J. A., et al. (2011). Mesoscale structure and oceanographic determinants of krill hotspots in the California Current: Implications for trophic transfer and conservation. Progress in Oceanography 91(4): 397-409.

Active acoustic surveys are frequently used to map krill distributions in diverse ecosystems around the globe. Santora et al. use this method in the California Current region to map krill abundance hotspots and identify trends in cross-shelf and alongshore variability. Their analysis of nine years of data reveal eight definite and two likely hotspots of krill abundance off the coast of California. The authors emphasize that knowledge of these hotspots can be used to inform conservation efforts, such as the development of marine protected areas for krill predators such as whales.

Kavanaugh, M. T., et al. (2016). Seascapes as a new vernacular for pelagic ocean monitoring, management and conservation. ICES Journal of Marine Science 73(7): 1839-1850.

Classifying types of and variability within discrete “seascapes” in the expansive, turbulent ocean can help scientists better understand the mechanisms and relationships that govern these environments. Kavanaugh et al. discuss a breadth of remote sensing methods for classifying seascapes and the advantages of this approach for dynamic ocean monitoring, management, and conservation. The authors emphasize the role that satellite remote sensing can play in characterizing habitats and marine communities. These include SeaWiFS, MODIS-Aqua, and VIIRS ocean color sensors, LIDAR and polarimetry techniques for quantifying ocean particle composition, as well as Sentinel and NASA Pre-Aerosol, Clouds, ocean Ecosystems missions that can improve the capacity to map benthic and pelagic habitat quality, which is of great interest to whales and other organisms. Finally, the authors discuss how these approaches can complement both spatially-explicit and dynamic management jurisdictions to improve monitoring and conservation capacity.

Cimino, M. A., et al. (2022). Western Gull Foraging Behavior as an Ecosystem State Indicator in Coastal California. Frontiers in Marine Science 8.

Certain “indicator species” can act as ecosystem sentinels, signaling changes in the marine environment that may be otherwise difficult to detect. In this study, Cimino et al. investigate western gulls on Southeast Farallon Island as a proxy of ecosystem state in coastal California. The researchers use six years of GPS gull tracking data to study variability in their foraging behavior in relation to ocean upwelling, prey availability, and spatial overlap with humpback whales. They find that gull movement patterns could act as an indicator of whale presence, and that deploying tags on gulls capable of transmitting real-time data could provide researchers with live metrics that can inform spatially-targeted management and conservation of humpback whales in this region.

Species Distribution Modeling

Ingman, K., et al. (2021). Modeling changes in baleen whale seasonal abundance, timing of migration, and environmental variables to explain the sudden rise in entanglements in California. PLoS One 16(4): e0248557.

Whale entanglements off the coast of California have increased dramatically since 2014. In this study, Ingman et al. use a 24-year time series of daily geo-located whale sightings to document changes in migration timing and the number of sightings in the Gulf of Farallones for gray, blue, and humpback whales. The authors use linear modeling to assess trends in migratory timing and identify the influence of local oceanography, regional, and basin-scale climate variables.
They find that humpback whale sightings increased over the study period, but blue and gray whale counts did not. In addition, humpback and blue whales arrived in the area earlier, resulting in longer exposure to fishing gear in the Gulf of Farallones and increased entanglement risk. The authors conclude that management efforts to decrease the temporal and spatial overlap between whales and fishing gear would decrease entanglement risk for whales in this region, especially during warm years.

Rockwood, R. C., et al. (2020). Modeling predator and prey hotspots: Management implications of baleen whale co-occurrence with krill in Central California. PLoS One 15(7): e0235603.

Understanding distributions of whales and their prey in time and space can facilitate management strategies that decrease conflict between humans and threatened wildlife. In order to develop this understanding off the central California coast, Rockwood et al. investigate the environmental drivers of distribution and abundance for humpback and blue whales, as well as two species of their prey, the zooplankton krill. The authors analyze krill observations collected through ship-based active acoustic profiling, geo-referenced whale observations from simultaneous shipboard marine mammal surveys, and in situ oceanographic measurements interpolated to create spatially corresponding rasters of environmental data. Hotspot analyses reveal the center of distribution for each species and areas of overlap in time and space, identifying areas for increased management efforts.

Barlow, D. R., & Torres, L. G. (2021). Planning ahead: Dynamic models forecast blue whale distribution with applications for spatial management. Journal of Applied Ecology, 58, 2493– 2504. doi: 10.1111/1365-2664.13992

The capacity to forecast whale distributions can allow managers to make temporally-specific decisions to lower entanglement risk to whales. In this study, Barlow and Torres develop forecast models for blue whales in the South Taranaki Bight region of New Zealand. They employ known ecosystem relationships and remotely sensed environmental data to develop and test ecological forecasts through Boosted Regression Tree machine learning models. The resulting forecasts predict sea surface temperature, net primary productivity, and blue whale habitat suitability up to three weeks in the future. In addition to sharing their results in this publication, the authors packaged these models for convenient stakeholder use, so that the New Zealand Department of Conservation can use this forecast tool in decision making.

Wikgren, Brooke et al. Modeling the distribution of the North Atlantic right whale Eubalaena glacialis off coastal Maine by areal co-kriging. Endangered Species Research 24 (2014): 21-31.

North Atlantic Right Whales are both critically endangered and heavily threatened by entanglement and ship strikes. Currently, no methods make use of all available data streams that characterize right whale distribution. In response, Wikgren et al. develop an areal co-kriging interpolation technique using ArcGIS to bring together data on whale distributions from surveys, opportunistic sightings, and satellite tags. They analyze distributions off the coast of Maine in irregularly shaped polygons representing lobster fishing zones, as gear from this fishery poses a primary entanglement risk to whales. The authors also design a mapping tool in which the modeled distributions are structured by user-defined polygons, allowing managers to best shape the maps to their needs.

Muhling BA, Brodie S, Smith JA, Tommasi D, Gaitan CF, Hazen EL, Jacox MG, Auth TD and Brodeur RD (2020) Predictability of Species Distributions Deteriorates Under Novel Environmental Conditions in the California Current System. Front. Mar. Sci. 7:589. doi: 10.3389/fmars.2020.00589

Access to sufficient oceanographic data can allow scientists to mathematically model the distributions of species of interest like whales, but collecting environmental data can be expensive, logistics-intensive, and difficult. In this study, Muhling et al. work with modeled environmental data fed by remote sensing satellite inputs, called the Regional Ocean Modeling System (ROMS). They use ROMS data to model the distribution of two key species in the California Current System, the Pacific sardine and northern anchovy, and test the capacity of the models to predict distributions under novel environmental conditions, such as ocean heatwave events. They find that the models lose substantial predictive skill in novel scenarios, suggesting that correlative relationships between animals and their environment can become unreliable during anomalous conditions. The authors note that modeling migratory species under future ocean conditions may be especially difficult.

GIS for Communication

Bolduc, Madison. The North Atlantic Right Whale. December 18, 2020.

Whale entanglement in fishing gear is often a contentious issue, involving diverse stakeholders including fishermen, marine resource managers, researchers, and interested members of the public. Conversations and action around the endangered North Atlantic Right Whale and their management in the northeastern United States and Canada are no exception. In this ARCGIS StoryMap, Madison Bolduc uses data visualization and explanatory text to build a narrative around the problem of right whale entanglement, conduct a risk analysis on areas of greatest concern, and share findings about the regions of greatest entanglement risk in the United States and Canada. Her webpage integrates multiple data streams and outputs, including geo-located whale strandings, ship tracklines, and maps showing calculated spatially-discrete risk levels. This tool is an effective communication piece for sharing findings and information about this contentious issue.

Read more about entanglement science and more: