Date of Award

Spring 4-5-2022

Document Type

Thesis: Open Access

Degree Name

MS Marine Science

Department

Environmental and Ocean Sciences

Committee Chair

Andrew Nosal

Committee Member

Jennifer Prairie

Committee Member

Camrin Braun

Abstract

While the movement patterns of large elasmobranch species have been studied extensively, those of smaller, mesopredatory species remain understudied. The shovelnose guitarfish (Pseudobatos productus) and the California bat ray (Myliobatis californica) are among the least studied elasmobranchs in the Southern California Bight. This study quantified the broad- and fine-scale movement patterns of these species using passive acoustic telemetry. Twelve guitarfish were surgically implanted with coded acoustic transmitters at a known aggregation site off La Jolla (San Diego County), California, USA and tracked for 849.5 days each, on average. Six bat rays were also implanted here and tracked for 1143.8 days each, on average. These animals were detected at 187 acoustic receiver stations between Point Conception, California, and San Quintín, Baja California, Mexico. Both species exhibited annual philopatry to the La Jolla tagging site, especially during the month of July, after traveling as far north as Santa Barbara, CA (221 km away; guitarfish) and San Miguel Island, Northern Channel Islands, California (259 km away; bat rays). Of the 34 receivers off La Jolla, a mean of 84.4% of guitarfish detections and 48.4% of bat ray detections occurred at just two acoustic receivers located on a sandflat in the lee of a submarine canyon. Guitarfish had a strong preference to soft substrate off La Jolla, while bat rays utilized both soft and hard substrates. This is the longest-duration acoustic tracking study of these batoid species to date, and the first to track California bat rays using passive acoustic telemetry.

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