Article

Effectiveness of descending devices to mitigate the effects of barotrauma among rockfishes (Sebastes spp.) in California recreational fisheries

Authors:
  • The Nature Conservancy, San Diego
  • UC Santa Cruz/ NOAA Fisheries affliate
Article

Effectiveness of descending devices to mitigate the effects of barotrauma among rockfishes (Sebastes spp.) in California recreational fisheries

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Abstract

Fishes caught from depth often suffer from barotrauma, which can result in high mortality rates (close to 100% for some species) when released at the surface. To mitigate for this, the recreational fishing community pro-actively developed several different types of descending devices designed to assist unwanted or prohibited fish back toward the bottom for release. Post-release survival using recompression techniques has been documented for some species, which has allowed fisheries managers to begin revising estimates of total fishing mortality in some cases, but the effectiveness of the different commercially-available descending device types has not been quantified. We conducted 24 Commercial Passenger Fishing Vessel charters at 11 sites along the coast of California, and invited volunteer recreational anglers aboard the charters to test the effectiveness of five different commercially available device types, and respond to a survey of their device preferences. During release, all fish were descended either to 46 m (150 ft) depth or directly to the bottom, whichever depth was shallower. While there were some significant differences between device types, all devices were effective for releasing rockfishes back to depth. Initial post-release mortality (defined as all mortality events observable from the vessel while fishing) across all devices was relatively low (7.5%) in capture depths less than 100 m, but increased significantly to 16.4% at capture depths from 100 to 135 m. Our results suggest that rockfishes should be released at least halfway to the bottom (preferably directly to the bottom) for the device to be effective in minimizing post-release mortality. The time required to use the devices averaged under three minutes regardless of device type, meaning that all device types could be used efficiently on deck, but anglers showed a clear preference for the SeaQualizer ™. This device produced some of the lowest release error rates and lowest initial post-release mortality of rockfishes aboard the charters, so angler preference coincided with device effectiveness. Collaborating with the recreational fishing community was an extremely important aspect to this study, provided more robust results, and fostered working relationships that can be built upon in future research projects.

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... While this technique has been shown to be beneficial in some cases, the general effectiveness of venting has had mixing results (Wilde, 2009;Brownscombe et al., 2017). The recent advent of commercially available descending devices now allows anglers to release fish back to their depth of capture without venting (Hochhalter and Reed, 2011;Runde and Buckel, 2018;Bellquist et al., 2019) and emphasizes the study of fish survival rates following recompression when barotrauma symptoms (e.g. bloating, organ displacement, and emphysemas) are largely reversed, but tissue damage caused by these symptoms may still be severe. ...
... In response, state and federal government, non-government organizations, and industry leaders in the recreational and commercial fishing communities came together in a massive education campaign to promote the release of rockfishes with descending devices to assist fish back to their depth of capture (Theberge and Parker, 2005;Bellquist et al., 2019). This led to a flurry of hyperbaric chamber and cage studies to test the survival of rockfishes if properly recompressed following barotrauma. ...
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... Descending devices (e.g. https://seaqualizer.com/product/seaqualizerdescending-device/) have proven highly effective across species (Butcher et al. 2012;Drumhiller et al. 2014;Bellquist et al. 2019) and avoid the potential of damaging organs during the venting process (discussed in Wilde 2009). Other recovery measures used by anglers include the pouring of carbonated beverages (e.g. ...
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... For example, lowering an affected animal to 50 m will reduce an equilibrated gas volume to one sixth of its volume at the surface. For examples of recompression devices, see Bellquist et al. (2019), DFO (2018) and NOAA (2020). ...
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... Therefore, to minimize the aforementioned sublethal consequences and potential mortality that are incurred due to capture in the commercial lobster fishery, avoidance tactics are recommended. If avoidance tactics are unsuccessful or unrealistic to implement, modified release practices which assist SR and LHS in returning to depth (i.e., descending devices) may have the potential to reduce short-term postrelease mortality (i.e., Bellquist et al. 2019). ...
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... Venting and recompression devices have been investigated to determine whether they increase postrelease survival of some physoclistous reef fish species (e.g., Drumhiller et al. 2014;Runde and Buckel 2018;Bellquist et al. 2019). However, despite this body of research, the relative effectiveness of venting versus descending remains uncertain. ...
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... All fish were placed in a live well to recover before they were released. Vermilion Rockfish were released at depth using SeaQualizer pressureactivated descending devices to reduce the effects of barotrauma (Bellquist et al., 2019;Jarvis and Lowe, 2008) and all pleuronectiform fishes were released at the surface. All fish handling and tagging methods were approved by the California Department of Fish and Wildlife (CDFW Scientific Collecting permit #3450) and the CSULB Institutional Animal Care and Use Committee (IACUC protocol #380). ...
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We analyzed data from the Marine Recreational Fishery Statistics Survey (MRFSS) to examine long-term trends in the Southern California Bight commercial pas-senger fishing vessel rockfish fishery. From 1980 to 1996 a total of 50 species were taken. There was a substantial decline in the overall catch per unit of effort (CPUE) during that time. For individual species we observed four general tem-poral patterns: (1) a steady decline throughout the period; (2) high CPUE from 1983 to 1986; (3) variable catches throughout the 1980s but extremely low catches from 1993 to 1996; and (4) variable catches through-out the entire period. Among the several species with particularly large declines were bocaccio (98.7%), blue rockfish (95.2%), and olive rockfish (83.0%)). Three species that were abundant in 1980 were absent by 1996 (chilipepper, swordspine, and yellowtail rockfishes). The number of species caught also decreased during the course of the survey. We analyzed length frequencies for a subset of the species. O n average, mean total length declined. This decline was due mainly to the removal of the larger size classes rather than to increased catches of juveniles. An extreme example was observed for vermilion rock-fish: over the course of the survey, the fishery changed from one comprising primarily adults to almost en-tirely juveniles. We conclude that the declines in rockfish catches in the Southern California Bight between 1980 and 1996 reflect reduced populations. These population declines probably result from poor long-term juvede recruitment, caused by adverse oceanographic conditions, as well as from essentially unregulated overfishing of adults and subadults, perhaps leading to recruitment overfishing.
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Cowcod (Sebastes levis) is a large (100-cm-FL), long-lived (maximum observed age 55 yr) demersal rockfish taken in multispecies commercial and recreational fisheries off southern and central California. It lives at 20-500 m depth: adults (>44 cm TL) inhabit rocky areas at 90-300 m and juveniles inhabit fine sand and clay at 40-100 m. Both sexes have similar growth and maturity. Both sexes recruit to the fishery before reaching full maturity. Based on age and growth data, the natural mortality rate is about M =0.055/yr, but the estimate is uncertain. Biomass, recruitment, and mortality during 1951-98 were estimated in a delay-difference model with catch data and abundance indices. The same model gave less precise estimates for 1916-50 based on catch data and assumptions about virgin biomass and recruitment such as used in stock reduction analysis. Abundance indices, based on rare event data, included a habitat-area-weighted index of recreational catch per unit of fishing effort (CPUE index values were 0.003-0.07 fish per angler hour), a standardized index of proportion of positive tows in CalCOFI ichthyoplankton survey data (binomial errors, 0-13% positive tows/yr), and proportion of positive tows for juveniles in bottom trawl surveys (binomial errors, 0-30% positive tows/yr). Cowcod are overfished in the southern California Bight; biomass during the 1998 season was about 7% of the virgin level and recent catches have been near 20 metric tons (t)/yr. Projections based on recent recruitment levels indicate that biomass will decline at catch levels > 5 t/yr. Trend data indicate that recruitment will be poor in the near future. Recreational fishing effort in deep water has increased and has become more effective for catching cowcod. Areas with relatively high catch rates for cowcod are fewer and are farther offshore. Cowcod die after capture and cannot be released alive. Two areas recently closed to bottom fishing will.
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We evaluated the external signs of barotrauma and 48-h post-recompression survival for 54 canary and 81 yelloweye rockfish captured at depths of 46–174 m, much deeper than a similar prior experiment, but within the depth range of recreational fishery catch and discard. Survival was measured using specialized sea cages for holding individual fish. The external physical signs associated with extreme expansion and retention of swimbladder gas (pronounced barotrauma), including esophageal eversion, exophthalmia and ocular emphysema, were common for both species at these capture depths and were more frequent than in prior studies conducted at shallower depths. Despite similar frequencies of most external barotrauma signs, 48-h post-recompression survival of the two species diverged markedly as capture depth increased. Survival of yelloweye rockfish was above 80% across all capture depths, while survival of canary rockfish was lower, declining sharply to just 25% at capture depths greater than 135 m. Fish of both species that were alive after 48 h of caging displayed very few of the external signs of pronounced barotrauma and had a high submergence success rate when released at the surface. Logistic regression analysis, using a combined data set from this and an earlier experiment conducted at shallower capture depths, was used to more broadly evaluate factors influencing post-recompression survival. For canary rockfish, depth of capture was negatively related to survival (P < 0.0001), but the surface-bottom temperature differential was not (P > 0.05). Exophthalmia and ocular emphysema were each negatively associated with survival for canary rockfish (P < 0.05). For yelloweye rockfish, no significant associations were found between post-recompression survival and capture depth, the surface-bottom temperature differential or any of the signs of pronounced barotrauma (P > 0.05).
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Rapid ascent during fishing capture can cause exophthalmia (‘pop eye’) in physoclistic fishes, resulting in stretching of the optic nerves and extraocular muscles, but it is not known whether exophthalmia affects vision temporarily or permanently. We used the optokinetic reflex test to assess changes in visual performance of rosy rockfish (Sebastes rosaceus) that had experienced exophthalmia. Vision was functional 4 days after recompression and was improved after 1 month of recovery evidenced by individuals being able to track both smaller and faster-moving gratings. Our results suggest that, after recompression, rosy rockfish recover from exophthalmia fairly rapidly and perhaps fast enough to minimize significant adverse impacts on survival. This measured recovery from exophthalmia, in addition to evidence of high short-term, post-release survivorship, shows that recompression of unwanted rosy rockfish may be a viable management technique, and may be appropriate for other rockfish species, some of which are at low population densities due to high fishing pressure.
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ABSTRACT We constructed a database for the Southern California commercial passenger fishing vessel (CPFV) fleet for the years 1959‐1998 using the daily fish reports from the Los Angeles Times. This database includes information on number of fish caught by species, landing port, land- ing date, and number of anglers. Comparison of this database to the,logbook,database maintained,by the California Department,of Fish and Game shows high correlation. Angler effort has been consistent throughout,the time series at about 620,000 passengers per year. The annual fish catch averaged 4.25 million fish from 1963 to 1991 but has declined since 1992 to 2.5 million fish in 1998. The data show a decided decline in the CPFV catch of rockfish species since the early 1980s; a possi- ble consequence of this decline appears to be a shift in effort toward less utilized species over the past decade, most notably ocean whitefish, California scorpionfish, cabezon, and more recently sanddabs. The CPFV fishery not only provides a recreational opportunity to residents and visitors to southern,Cali- fornia but also contributes to local economies. This fleet’s catches, combined with those of private recreational an- glers, are substantial enough to impact fish populations, particularly in regional areas. The database, which will be available on the NOAA-NMFS Southwest Fisheries
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Variables affecting the short-term survival of snapper (Pagrus auratus) captured using commercial fish traps and subsequently released were investigated by holding the fish in cages. A logistic regression model showed that capture depth had the greatest affect on short-term survival of snapper, with no mortalities observed from depths of less than 21m and ∼2% from depths of less than 30m. Mortality of snapper increased rapidly after 30m and was ∼39% between capture depths of 30 and 44m and ∼55% between capture depths of 45 and 59m. Survival was also effected by fish length, with smaller fish being more likely to die. The rate of ascent of captured snapper and the density of fish in cages were kept reasonably constant and did not appear to affect survival. The number of snapper swimming upside-down prior to being returned to the sea floor in cages was not a good predictor of mortality. Future studies that use cages to assess discard mortality rates would benefit from underwater video observations of fish behaviour. The results demonstrate that the discard mortality of snapper should be considered when managing the fishery in New South Wales, Australia.
Article
The effectiveness of deepwater release at improving the 17-d survival of discarded yelloweye rockfish Sebastes ruberrimus was determined by comparing an estimate of survival for individuals released at depth with an estimate of submergence probability for individuals released at the water's surface. A mark–recapture study was used to generate a maximum likelihood estimate of the 17-d survival probability of yelloweye rockfish (n = 182) caught by hook and line (depth = 18–72 m) and subsequently released at depth. The average Cormack–Jolly–Seber survival probability for yelloweye rockfish released at depth was remarkably high (0.988; 95% confidence interval = 0.478–0.999) and positively correlated with individual total length. Survival probability was not significantly influenced by the range of capture depths explored in this study or by exposure to barotrauma and other capture stressors. The submergence success of yelloweye rockfish released at the water's surface was 0.221 (95% confidence interval = 0.149–0.315), suggesting that the maximum survival potential of individuals released at the surface is low. The results of this study indicate that the average survival of discarded yelloweye rockfish can be substantially improved by deepwater release.Received March 25, 2011; accepted June 22, 2011
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From p. 27: "The mean length of rockfish caught in the late 1970s increased as CPFVs moved into deeper water. The mean length was generally larger for deepwater species than for shallow-water species, and large individuals were caught from 1977 through 1983. A surge of new recruitment after the 1982-83 El Niño produced a sharp drop in mean length of several important species and a decline in combined rockfish mean length. Mean lengths did not recover to the high levels of 198283 despite the growth of these recruits and the continued emphasis on deepwater species through 1991."
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