Rice’s Whales

The Team: Lance P. Garrison (Lead Investigator, NOAA, lance.garrison@noaa.gov) Melissa Soldevilla (NOAA), Keith Mullin (NOAA), John Hildebrand (Scripps Institution of Oceanography, University of California San Diego), Michael Heithaus (Florida International University), and Jeremy Kiszka (Florida International University)

Technical Monitor: Vicki Cornish (vcornish@mmc.gov) and Barb Zoodsma (barb.zoodsma@noaa.gov)

Federal Program Officer/Point of Contact: Frank Parker (frank.parker@noaa.gov)

This project began in June 2017 and ended in May 2021.

Award Amount: $ 2,312,275

Why it matters: The Gulf of Mexico Rice’s whale population is estimated at 33 individuals and very little is known about this species. This project will gather and share information on how this small, resident population of whales relies on the northeastern Gulf of Mexico food web and will provide critical information to managers for recovery and restoration activities. This project will also examine an open ocean food web in the Gulf of Mexico and determine how it supports a range of species including finfish and rare whales.

What the team did: Using visual and acoustic monitoring, environmental measurements, collection of tissues from free-swimming whales, studies of prey distribution and composition, and deployment of animal-borne telemetry tags, the investigators will develop models and conduct analyses that provide information to managers and inform restoration and population recovery activities.

Summary of Outcome: In this study, we employed a multi-faceted approach to better understand the trophic ecology and habitats of this species. During three large vessel cruises, we employed visual and passive acoustic monitoring of whales, environmental sampling, scientific echosounder sampling, trawl sampling of prey, biopsy sampling for genetic and stable isotope analyses, photogrammetry from UAS systems, photo-identification studies, deployment of animal-borne tags, and eDNA methods. We integrated these data with visual survey data and photo-identification data collected by that National Marine Fisheries Service over the last two decades. The study demonstrated that Rice’s whales occur in regions of elevated productivity associated with upwelling of intermediate depth water onto the outer continental shelf and seasonal inputs of high productivity surface waters from coastal sources. Within the core habitat, dynamic oceanographic conditions support spatially and temporally variable aggregations of prey including fish occurring in dense schools in near-bottom waters at depths of 200-300m. Telemetry tags demonstrate that whales forage by diving nearly continuously during daylight hours. While feeding, whales typically undertake 1-2 lunges per dive and execute stereotypical behaviors that may be associated with the detection and aggregation of prey. Based upon stable isotope analysis and trawl data, it appears that the primary prey species for Rice’s whales are a schooling demersal fish, Ariomma bondi, that typically ranges from 100-200mm in body length. Other prey species include small, vertically migrating fish and squids. Photographic data collected during the current study and previous studies demonstrate considerable variability in the body and skin condition of individual animals over time. Energy budgets developed from the integration of tag data, trawl and acoustic prey distribution data, diet information, and prey proximate composition will help to assess the degree to which Rice’s whales are prey resource limited. The results from this study are currently being used to inform management and conservation actions, the development of recovery plans, and the identification of critical habitat as required under the Endangered Species Act.