Characterizing activity and assessing bycatch survival of Pacific halibut with accelerometer Pop-up Satellite Archival Tags

Abstract

Background: Pacific halibut support high-value commercial and sport fisheries in the north Pacific Ocean, making survival of Pacific halibut bycatch in trawl fisheries an important management concern. We present a method for characterizing activity and inferring survival of Pacific halibut based on accelerometer data from Pop-up Satellite Archival Tags (PSATs). A PSAT attached to a fish with a dart and tether floats freely above the fish in a vertical orientation when the fish is stationary, but switches to a more horizontal orientation when towed behind an active fish. We hypothesized that characteristic changes in PSAT orientation associated with activity could be detected by accelerometers and summarized for transmission by PSATs to provide valuable information on fish activity. Results: We developed procedures for inferring survival of Pacific halibut with accelerometer PSATs based on a progression of analysis steps that linked PSAT orientation, PSAT acceleration data, and Pacific halibut activity patterns. Relationships between PSAT orientation and Pacific halibut activity were confirmed by observations of PSAT orientation on Pacific halibut swimming in the laboratory and comparisons with depth data from tags on free-ranging Pacific halibut. We developed two metrics summarizing 1 Hz acceleration data for transmission to the Argos satellite network. The "knockdown" metric records abrupt changes in vertical acceleration, indicating both initiation of swimming bouts and sustained swimming behavior, and is robust to the effects of tidal currents. The "%tilt" metric records the amount of time the tag tilts past a vertical orientation threshold and captures the proportion of each time bin that the fish is active. These PSAT metrics revealed diel behavior and three activity modes present in free-ranging Pacific halibut that allowed inference of survival when compared to PSAT data from fish carcasses and weighted tags. Conclusions: Accelerometer PSAT metrics developed in this study revealed Pacific halibut activity patterns, and thus survival, and may be extended to other fish species. Economical accelerometer PSATs can allow larger sample sizes that enhance bycatch survival studies while detecting fish activity in flat study areas. PSAT advantages over other survival estimation methods include providing outcomes for all specimens during exposure to natural conditions.

Pop-up satellite archival tags reveal evidence of intense predation on large immature Chinook salmon (Oncorhynchus tshawytscha) in the North Pacific Ocean

“…Pop-up satellite archival tags (PSATs), an electronic tag that records environmental variables while attached to a fish, offers a viable method to study mortality and predation of tagged individuals (Lacroix 2014;Nielsen et al 2018;Thorstad et al 2013). On a preprogrammed date, the tag releases from the fish, floats to the surface of the ocean and transmits data to satellites, which are then retrieved by project investigators.…”

“…On a preprogrammed date, the tag releases from the fish, floats to the surface of the ocean and transmits data to satellites, which are then retrieved by project investigators. Because PSATs do not rely on recapture of tagged individuals for data retrieval, they are a valuable tool to assess survivorship, because data can be retrieved from individuals that experience mortality (Benson et al 2018;Lacroix 2014;Nielsen et al 2018). Therefore, the objectives of this study were to examine diagnostic evidence of predation on large Chinook salmon from depth, temperature, and light records collected during recent satellite tagging research.…”

A scalable, satellite-transmitted data product for monitoring high-activity events in mobile aquatic animals

“…Garnering such evidence can contribute to conservation planning and management, such as assessing climate change vulnerability or species use in protected and unprotected areas [25][26][27]. Following previous studies [28,29] (Table 1), we aim to address this area of research by pairing a compressed metric of activity with environmental data (depth and temperature) and location data (geolocation). Specifically, we present a novel, satellite-transmittable, acceleration-derived metric of high-activity based on measurements obtained from pop-off satellite archival tags (PSAT).…”

“…However, if attempting to transmit an extensive amount of data (e.g., three concurrent time-series), due to the abovementioned issues, there may be some gaps in the data. To address this limitation, researchers can compress the data's dimensions, either by combining several data into one metric [34] or by recording events based on a predetermined algorithm which incorporates several streams of data [17,28,29], and/or compress the data temporally, Table 1 Accelerometer-derived metrics of activity and/or behaviour for marine animals, including the targeted activity or behavior, equipment used, and example study or studies using the metric [19] ODBA (overall dynamic body acceleration) (Absolute acceleration along x, y, and z-axes) -(static acceleration due to gravity)…”

An Integrative Method for Characterizing Marine Habitat Features Associated With Predation: A Case Study on Juvenile Steller Sea Lions (Eumetopias jubatus)

“…Internal VHF devices and mark-recapture efforts have been used to successfully monitor survival of marine animals for periods beyond 1 year, but detection range, regional coverage, and determination of mortality locations are still limited using these methods (Horning and Hill, 2005). To overcome these limitations, external and implantable satellite tags have been developed that utilize collected sensor data (e.g., light levels, temperature, depth changes) to detect mortalities (Horning and Hill, 2005;Horodysky and Graves, 2005;Nielsen et al, 2018). Following a mortality detection, external tags can be programmed to detach, float to the sea-surface, and transmit data through global satellite systems (Kerstetter et al, 2003;Seitz et al, 2019).…”