Currently, in the United States, there are few sedatives available to fisheries professionals that are safe, effective, and practical. Chemical sedatives, including tricaine methanesulfonate (MS‐222), carbon dioxide (CO2), benzocaine, and eugenol may be used to sedate fish, though none of these compounds are currently approved by the U.S. Food and Drug Administration as immediate‐release fish sedatives. Another option is the use of electricity to temporarily immobilize fish. Few studies have assessed the efficacy of these options for immediate‐release sedation in side‐by‐side comparisons. We evaluated the use of MS‐222 (150 mg/L), CO2 (∼400 mg/L), benzocaine (150 mg/L), eugenol (60 mg/L), and a commercially available electrosedation unit (30 Hz pulsed DC, 60 V, 25% duty cycle, 3‐s exposures) to induce hybrid striped bass (white bass Morone chrysops × striped bass M. saxatilis; 510 ± 12 g [mean ± SE]) to stage IV anesthesia or sedation. Induction times were shortest (0.2 ± 0.1 min) when electrosedation was used and longest (2.5 ± 0.1 min) when CO2 was used; the induction times for the other chemical sedatives varied (<2 min). Recovery times were longest for eugenol (5.2 ± 0.4 min postinduction) and benzocaine (4.0 ± 0.4 min); however, the difference in recovery time between these two treatments was not significant or between recovery times for benzocaine and the remaining sedatives (∼3–4 min). Physiological responses varied but were consistent with the generalized stress response. Circulating levels of cortisol, glucose, and lactate increased after sedation, and though response magnitude and duration varied somewhat among these variables, these changes were resolved within 6 h. Changes in plasma osmolality and hematocrit were less overt and varied less among the sedatives. Electrosedation may be a suitable tool for quickly sedating hybrid striped bass; however, all of the sedatives evaluated were effective at the doses and strengths used and some may be better suited to certain applications than to others.
Sedating fish before handling minimizes the risk of injury to both fish and handler and may also minimize the fish's stress response. We conducted two experiments to quantitatively compare induction and recovery times of largemouth bass Micropterus salmoides sedated with tricaine methanesulfonate (MS‐222), eugenol, benzocaine, carbon dioxide (CO2), or electrosedation (pulsed DC). We also assessed the fish's hematological profile following sedation with MS‐222, eugenol, and electrosedation. Induction times varied significantly among the sedatives evaluated; electrosedation yielded the fastest inductions (0.2 ± 0.1 min; mean ± SE) and CO2 yielded the slowest (3.6 ± 0.1 min). Times to recovery of equilibrium and responsiveness to tactile and visual–auditory stimuli also varied, ranging from 1.8 ± 0.3 to 3.7 ± 0.3 min and from 2.3 ± 0.3 to 4.0 ± 0.3 min, respectively, depending on the sedative used. Plasma cortisol concentrations were elevated at 0.5 h postsedation among fish sedated with eugenol and MS‐222, whereas cortisol levels of electrosedated fish were comparatively low and stable throughout the experiment. Conversely, plasma glucose and lactate levels increased markedly from 0.5 to 2 h postsedation among electrosedated fish, whereas the responses among fish treated with eugenol or MS‐222 were weak or negligible. Our results indicate that electrosedation, benzocaine, eugenol, and MS‐222 are all effective in quickly sedating largemouth bass. Physiological and behavioral data suggest that largemouth bass generally recover within 6 h of sedation using MS‐222, eugenol, or electrosedation.
Fish oil (FO) sparing is common in aquafeed formulation; however, some alternative lipids have proven to be more successful than others in ensuring adequate growth and maintenance of desirable fillet fatty acid (FA) composition. Depending on the lipids used, grow‐out feeds influence the FA composition of the tissues of “lean‐fleshed” fishes and their responsiveness to subsequent tailoring during finishing. To address whether different lipid sources similarly influence growth performance and tissue composition of a “fat‐fleshed” fish, rainbow trout Oncorhynchus mykiss were reared on feeds containing FO or a 50:50 blend of FO and coconut oil (COCONUT), palm oil (PALM), standard soybean oil (STD‐SBO), hydrogenated soybean oil (HYD‐SBO), low‐18:3(n‐3) (alpha‐linolenic acid) soybean oil (LO‐ALA‐SBO), or low‐18:3(n‐3) canola oil (LO‐ALA‐CAN). Two saturated FA (SFA)‐enriched lipids derived from the processing of cottonseed (SFA‐COT) or soybean (SFA‐SBO) were also evaluated as 50% FO substitutes. After 7 weeks, growth performance was largely unaffected by dietary lipid source. Fillet levels of long‐chain (LC) polyunsaturated FAs (PUFAs) among fish that received the HYD‐SBO, LO‐ALA‐SBO, SFA‐SBO, and SFA‐COT feeds were equivalent to levels in fish that received the FO feed, despite an approximate 50% reduction in dietary LC‐PUFA intake. Our results indicate that feeds containing a blend of FO and novel soy‐ or cottonseed‐derived lipids yielded equivalent growth performance and fillet LC‐PUFA content in rainbow trout. The use of STD‐SBO, COCONUT, PALM, or LO‐ALA‐CAN did not impair growth or efficiency but did alter the fillet FA profile. Rainbow trout appeared to differ somewhat from other fishes in terms of dietary influence on tissue FA profile; however, the pattern of greater LC‐PUFA retention in fish reared on SFA‐rich feeds appears to be largely consistent among the fish taxa we have assessed.Received January 19, 2010; accepted July 25, 2010
Fish oil sparing has proven difficult for some fish species, especially marine carnivores like White Seabass Atractoscion nobilis that require one or more long‐chain polyunsaturated fatty acids (LC‐PUFAs). Recent studies have suggested that the use of saturated fatty acid (SFA)–rich lipids instead of C18 polyunsaturated fatty acid–rich (C18 PUFA) lipids may be advantageous in maintaining tissue levels of LC‐PUFAs; SFA‐rich lipids may also offer a strategic advantage in terms of meeting the LC‐PUFA requirements of marine carnivores while minimizing dietary fish oil inclusion. Accordingly, we assessed the performance and tissue fatty acid composition of White Seabass (3.8 ± 0.2 g [mean ± SE]) fed diets containing fish oil or graded levels of C18 PUFA–rich standard soy oil or SFA‐rich hydrogenated soy oil (replacing 25, 50, 75, or 100% of dietary fish oil) for 8 weeks. Feed conversion ratio, weight gain, and specific growth rate were not impaired by partial or complete replacement of dietary fish oil with hydrogenated soy oil; however, fish oil sparing with standard soy oil was associated with declining performance. The tissue fatty acid profiles of fish fed the hydrogenated soy oil–based diets were very similar to those of fish fed the fish oil–based feed, but the standard soy oil–based feeds resulted in concomitant loss of n‐3 fatty acids and LC‐PUFAs. In all cases, the magnitude of the dietary effect was greater among liver and fillet tissues than among brain and eye tissues. These data suggest a limitation, potentially related to LC‐PUFA deficiency, associated with replacing fish oil with standard soybean oil, but not with hydrogenated soybean oil. Our data suggest that the LC‐PUFA requirements of White Seabass can be effectively reduced by feeding SFA‐rich alternative lipids, allowing for a greater level of fish oil sparing without growth impairment or tissue profile modification than is possible with C18 PUFA–rich lipids.
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