Projects | Michaela A. Kratofil

Delineating Biologically Important Areas

Mon, 01 Jan 0001 00:00:00 +0000

In 2015, Ferguson et al. coordinated an effort to define biologically important areas (BIA) for cetacean stocks in US waters, using a combination of information from the scientific literature, unpublished data, and expert knowledge. This information was then used to develop written narratives and an interactive map for each species or stock and their corresponding BIAs (seasonally or year-round). BIAs include areas that are important for migratory, reproductive, and feeding purposes, as well as areas used by small and resident (i.e., non-migratory) populations. These areas were created to serve as a tool for managers, researchers, and the public for analyzing and planning cetacean conservation and species protection initiatives required under US statutes (e.g., minimizing impact from anthropogenic activities). Visit the current interactive BIA (CetMap) here.

Now, five years after the initial effort, Ferguson et al. and regional cetacean experts across the US are reconvening to both update and improve the BIA delineation process. My role in this round of BIAs will be supporting the Hawaii and US West Coast leads in the delineation of cetacean BIAs in those regions, mainly assisting with analyses of data being used to support BIA delineation.

Drivers of variance in pollutant and stable isotope levels in Hawaiian false killer whales

Mon, 01 Jan 0001 00:00:00 +0000

False killer whales are long-lived apex predators, making them more susceptible to bioaccumulation of persistent organic pollutants. There are three genetically distanct stocks of false killer whales in the Hawaiian Islands: a pelagic, Northwestern Hawaiian Islands (NWHI), and main Hawaiian Islands (MHI) stock. The latter population is comprised of at least 4-5 cohesive social groups or “clusters”, consisting of highly-related and regularly-interacting individuals. The MHI stock was listed as “endangered” in 2012 in light of precipitous decline over recent decades. Among the major threats to their long-term viability was the risk of adverse health effects associated with exposure to perisistent organic pollutants (POPs). We conducted a comprehensive study on how POP levels are influenced by life history characteristics and social clusters, and identified demographics at greatest risk of effects associated with exposure. We also assessed variability in stable isotope values among social clusters to gain insight into MHI foraging ecology.

False killer whale movements in relation to FADs

Mon, 01 Jan 0001 00:00:00 +0000

Fish aggregating devices (FADs) are buoys that are designed to attract aggregations of pelagic fishes that naturally associate with floating objects; the purpose of FADs is to enhance fishermen’s catch. However, FADs may also attract false killer whales that pursue the same prey fishes, and consequently exacerbate the risk of harmful fisheries interactions. More broadly, this research will help discern whether FADs have an influence on false killer whale space use which ultimately informs our understanding of their occurrence and associated risk to anthropogenic activities. Using movement data from 65 satellite tagged false killer whales between 2007-2021, I will examine space use and movement behavior in relation to State-sponsored FAD arrays and assess variation among demographics and over different spatial and temporal scales. I presented preliminary results of these findings at the virtual 7th International Bio-Logging Symposium in October 2021, and an expansion of this analysis will constitute my Master’s thesis.

To learn more about Hawai’i’s State-sponsored FADs: https://www.himb.hawaii.edu/FADS/

Geospatial analyses to inform false killer whale interactions with fisheries

Mon, 01 Jan 0001 00:00:00 +0000

Hawaiian waters are home to a population of false killer whales that primarily occupy insular regions of the islands. Following a precipitous decline observed over recent decades, this population was listed as “endangered” under the US Endangered Species Act in 2012. It is speculated that the greatest threat to this population are interactions with fisheries (through depredation) and bycatch. However, understanding the severity of bycatch issues requires both abundance estimates and rates at which bycatch and/or interactions occur. The most recent abundance estimate for this population estimated only around 167 individuals comprise the population, distributed among at least 5 social groups or “clusters” that vary by spatial use. Obtaining information from fishermen on interactions or bycatch with false killer whales has been challenging for several reasons. Namely, a speculated lack of reporting by fishermen due to fear of penalization. In additon, there are several other “blackfish” species that inhabit Hawaiian waters and therefore are often confused with other species. Unfortunately, Fisheries Observer Programs are not implemented for nearshore fisheries that are suspected to interact with endangered false killer whales the most. Here we used long-term data sets (2007-2018) of false killer whale satellite tag data and commercial fishery catch logs to assess spatiotemporal trends. We then used these two data streams to develop indices of overlap to identify fisheries and regions where interactions would be most likely to occur, in efforts to target fishermen who may be most qualified to assist in development of bycatch solutions.

Movement modelling for sonar received level estimation

Mon, 01 Jan 0001 00:00:00 +0000

Estimating individual received levels (RL) of sound during mid-frequency sonar activities requires knowledge of the location of the sound source (and level of sound emitted) and position of the focal individual. With the former already known, a sound propagation model is used to estimate sound levels through space and time while accounting for influences of static variables such as bathymetry. To obtain the animal’s position, satellite tags are deployed before sonar activities begin and locations are estimated via the Doppler effect and processed by Argos CLS location algorithms. However, these locations are accomodated with substantial error inherent with cetacean telemetry (PTT tags), such as tag placement, latitudinal range of satellites, and animal behavior. A tagged animal must surface in order for an observation to be made between the tag and the satellite; the surfacing period must be long enough to transmit message(s) and there also must be a sufficient number satellites available to detect the tag platform. The development of Fastloc-GPS tags are an improved alternative to Argos satellite-only transmitting tags by providing much more accurate positions, however these tags are of increased cost (and never recovered) and are often only deployed on prioritized species that are opportunistically encountered. Consequently, RL estimates can be greatly biased by positional uncertainty. For this project, we aim to account for positional uncertainty by using state-space movement models that incorporate error associated with positions transmitted from deployments on odontocetes around Kaua‘i. More specifically, we use error ellipse information that is estimated from the Kalman filter location algorithm (processed by Argos CLS) to formulate an error model that is incorporated into movement models. We use dive behavior data archived by tags to estimate animal positions in x, y, and z planes, as estimated sound varies by depth. In addition, we are experimenting with options to adjust model fitted movement paths for positions unrealistically close to shore, not commensurate with recorded dive depth, or on land (did you know that dolphins can climb mountains?). To see past reports and publications on RL estimation and behavioral response studies, visit www.cascadiaresearch.org/publications.

Movements of pantropical spotted dolphins in Hawaiian waters

Mon, 01 Jan 0001 00:00:00 +0000

Genetic studies and sighting distributions were used to delineate four stocks of pantropical spotted dolphins in Hawaiian waters: a pelagic stock and insular stocks off Hawaiʻi, Maui Nui, and Oʻahu. Information on short-term movements and space use in Hawai‘i is limited, yet such information is critical to their conservation, particularly in light of recent documentation of frequent interactions between fishing vessels and spotted dolphins throughout the main Hawaiian Islands (Baird & Webster, 2020). In this project we are characterizing spotted dolphin movements derived from satellite tag data and relating them to environmental features and current designated stock boundaries, finding that current designated boundaries are not adequate for some island-associated populations. In addition, we are evaluating movement behavior (e.g., move persistence) over diel and lunar temporal cycles for potential inference on their foraging ecology.

Link to the original Pacific Science Review Group report: https://www.cascadiaresearch.org/files/publications/Baird-PSRG-2019-15-spotted_movements.pdf

References: Baird, R.W. and D.L. Webster. 2020. Using dolphins to catch tuna: assessment of associations between pantropical spotted dolphins and yellowfin tuna hook and line fisheries in Hawaii. Fisheries Research doi:10.1016/j.fishres.2020/1205652

Courbis et al. 2014. Multiple populations of pantropical spotted dolphins in Hawaiian waters. Journal of Heredity 105(5): 627-641. doi: https://doi.org/10.1093/jhered/esu046

Oleson et al. 2013. Island-associated stocks of odontocetes in the main Hawaiian Islands: a synthesis of available information to facilitate evaluation of stock structure. PIFSC Working Paper WP-13-003. Pacific Islands Fisheries Science Center.