Habitat use and activity patterns of Deacon Rockfish (Sebastes diaconus) at seasonal scales and in response to episodic hypoxia.

Identification Information

Citation

Originator: Marine Fisheries Research Project

Publish Date: TBA

Online Link: None

BPA Project #:

Contact Information

Agency: Oregon Department of Fish and Wildlife

Name: Leif Rasmuson

Job Position: Marine Fishery Research Project Leader

Telephone: 541-867-0300 x231

E-Mail Address: leif.k.rasmuson@odfw.oregon.gov

Description

Abstract: Knowledge of fish movements and residency are key to design and interpretation of results from bioacoustic sonar and visual survey methods, which are being developed as tools for use in nearshore rocky reef surveys to estimate biomass and species composition. Fishers in Oregon report that an important component of the nearshore catch, Deacon Rockfish (Sebastes diaconus), become unavailable to harvest seasonally, and suggest periodic migration away from nearshore reef areas. Seasonal and spatial variation in landings data potentially support this theory. We used a high-resolution acoustic telemetry array and a combination of presence/absence receiver arrays, to study the daily and seasonal movements and the activity patterns of 11 acoustically tagged Deacon Rockfish on a nearshore rocky reef off Seal Rock, Oregon. Over the 11-month study period, most fish (n=6) exhibited high site fidelity. For the duration of the high-resolution array (5 mo), these fish had small home ranges (mean 95% KDE=4907 m2) and consistent activity patterns, except during seasonal hypoxia (defined as dissolved oxygen concentration [DO] < 2 mg l-1). During the summer months, resident fish were strongly diurnal with high levels of daytime activity above the bottom in relatively rugose habitat, followed by nighttime rest periods in deeper water in habitat of relatively less rugosity. During hypoxia, fish exhibited moderate activity levels with no rest periods and moved well away from their core activity areas on long, erratic forays. Wintertime activity levels were moderate with less defined daily patterns, but fish continued to remain within the array area. We suggest that Deacon Rockfish remain on nearshore reefs throughout the year, but their visual capabilities and prey preferences for seasonally occurring planktonic organisms strongly influences their catchability. Habitat use and activity patterns exhibited by Deacon Rockfish are conducive to bioacoustic sonar and visual survey methods if season, daylight, and oxygen levels are considered.

Purpose:

Time Period of Content: April 2016-April 2017

Geographic Extent: Seal Rock Reefs inshore of 30 m contour (Reef is located between Newport and Waldport Oregon)

Status: Final

Use Constraints: None.

Format: csv, zip, gdb, dir, dat, nit, atx

Data Quality Information

Lineage-Source: We used two different acoustic array designs for summer and winter to maximize tag detections, in consideration of habitat and ocean conditions. The summer array (April-September) included a high-resolution VPS (Vemco Positioning System) inner grid and outer perimeter presence/absence “fence” of receivers to detect any fish leaving the area. Range testing in a rugose, high relief area of the array provided worst-case detection statistics through a range of swell and wind conditions and determined receiver spacing. The VPS grid detection area encompassed 2.23 km2 and included 21 VR2W receivers with co-located V16 coded synctags (V16T-4L and V16-4L) moored at 250 m spacing, plus two centrally-located V16 reference tags (Vemco, Nova Scotia, Canada). The 18-receiver perimeter fence was deployed on three sides of the array (we excluded the shallow, shoreline side) and positioned 1200 m outside of the VPS array with moorings depths ranging from 12-39 m. The perimeter fence was 9.74 km long with 500 m spacing between receiver moorings. Acoustic receivers and synctags were positioned 3 m and 4 m off bottom, respectively. Ocean conditions in Oregon during winter months (October-March) are typified by large, energetic storms which generate considerable acoustic noise and interference with tag detections, so for the winter array we removed all co-located synctags to increase fish tag detection probability. The winter array had 9 receivers spaced 350 m apart covering an acoustic detection area of approximately 2.08 km2 (Fig 1), to acquire presence/absence only data. Acoustic receivers for both arrays were downloaded and serviced bimonthly on average. A Sea-Bird SBE16plusV2 (CTD), equipped with a SBE43 oxygen sensor was moored in 27 m of water depth at the NW corner of the VPS array, to record conductivity, temperature, depth and dissolved oxygen (Sea-Bird Electronics, Bellingham, WA, USA). The CTD was positioned 1 m off bottom and sampled one time every 60 minutes, during the summer months. The CTD was downloaded and serviced approximately bimonthly and was removed for winter. Fish were tagged with V13AP coded acoustic transmitters (69 kHz, 153 dB power output, 13x 42 mm, pressure sensing to 136 m) which transmit a unique ID, depth (m) and an acceleration value (m s-2) which is used as a measure of activity (Vemco, Nova Scotia, Canada).

Data Information

No data information was supplied.

Entity and Attribute Information

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