Recompression Devices: Helping Anglers Fish Smarter
Is Barotrauma Keeping You Up? Try Getting Down with Recompression!
Links to our creative artists:
The Fin Art of Ray Troll
Ray Troll/Russell Wodehouse & The Ratfish Wranglers
Ray Troll/Russell Wodehouse & The Ratfish Wranglers Facebook
View more videos on the effort:
Bocaccio tagging and recompression Cowcod tagging and recompression Researcher's catch and resubmerge effort
Rockfish (Sebastes spp.) experience high discard mortality rates from a condition called barotrauma, which is caused by the change in pressure during capture. Excessive buoyancy from barotrauma makes it difficult for many rockfish species to submerge under their own power and these discarded rockfish are often left floating on the surface where they can succumb to thermal shock, suffocation, and/or predation. Recently, field-based recompression devices have been suggested as a way to greatly reduce bycatch of unwanted or protected species. Though several studies have shown a high potential for survival following recompression, their focus has been on movement and site fidelity rather than survival and have typically tagged subadult fish captured from relatively shallow depths.
For more information:
California Sea Grant brochure on barotrauma
The Fisheries Resources Division staff has initiated a study on post-release survival of rockfish following field recompression. The goal of this study is to determine the survival rate of rockfish species captured from depths greater than 100 m and subsequently recompressed using weighted release devices. These fish are monitored using electronic tags for up to 4 months to evaluate changes in behavior over time and develop estimates of mortality of released fish.
We have tagged five different species of rockfish (cowcod, S. levis; sunset rockfish, S. crocotulus; bocaccio, S. paucispinis; starry rockfish, S. constellatus; and bank rockfish, S. rufus) captured primarily from 150 m to 180 m depths off the coast of Southern California. After assessing overall barotrauma injury and taking measurements and samples, these fish are externally tagged with Vemco V9AP accelerometer and pressure transmitter tags. Immediately after the tags are attached, rockfish are recompressed to depths between 40 m to 75 m using a weighted cage. The release cage used is equipped with a video camera and a pneumatic opening door that can be controlled from the boat. With this “cage cam,” we are able to monitor rockfish as they are recompressed and note condition and behavior of fish upon release. Using these observations along with the tag data and depth of capture information we hope to develop a minimum release depth recommendation for anglers.
Temporary moorings attached to VR2W acoustic receivers were deployed in the vicinity of the fishing/tagging site in an array designed to get good signal coverage of the rockfish habitat on this bank in order to continuously monitor the tagged fish. The receivers monitor movement patterns and activity of tagged fish in order to assess post-release survival.
Tag data from a 47.5 cm bocaccio showing post-release survival and from a 41.5 cm bank rockfish showing post-release mortality. Tag data from all 50 tagged rockfish are currently being analyzed to determine survival rates and to look for correlations between survival, depth of capture, external barotrauma indicators, and species.
Increased resolution of the depth profile for the 47.5 cm bocaccio shown above. Shortly upon release this fish resumed a consistent diel depth distribution, being higher in the water column during the day (white) and deeper at night (gray).
Additionally, a subset of rockfish are collected for an analysis of internal injury. Rockfish were dissected to evaluate internal injury as a result of barotrauma (i.e., swimbladder rupture, hemorrhaging) and tissues known to be susceptible to barotrauma injury (i.e., heart, head kidney, and rete mirabile) are removed for further histological examination.
Temporary Moorings Attached to VR2W Acoustic Recievers
Recompression Cage used during study
Anglers can use homemade recompression devices such as an inverted milk crate connected to a length of rope or purchase one of several commercially made products from the following websites.
Please direction all questions to John Hyde at firstname.lastname@example.org or Nick Wegner at email@example.com