To determine the effects of electrically and chemically induced immobilization on postspawn broodstock and their progeny, age-2 and age-3 female broodstock and age-2 male broodstock of brown trout Salmo trutta were immobilized with electricity or tricaine methanesulfonate (MS-222), stripped of their eggs or milt, and weighed. Eggs taken from electrically immobilized females were fertilized with milt taken from age-2 males that were immobilized with electricity, and eggs taken from females immobilized with MS-222 were fertilized with milt taken from age-2 males that were immobilized with MS-222. After spawning, the mortality and weight of broodstock were compared twice over a 6-month period. Egg viability and growth of offspring fry from each treatment group were also compared. Electricity induced complete and consistent immobilization in brown trout broodstock. Electrically immobilized fish were more easily handled than fish immobilized with MS-222; however, electrically immobilized fish survival (70%) was significantly less than fish immobilized with MS-222 (83%). Broodstock growth differences were only noted at 6 months postexposure, when the mean weight of electrically immobilized fish was slightly less than the weight of fish immobilized with MS-222. Broodstock immobilization by electricity did not reduce egg viability or fry growth.
The objective of this study was to develop a procedure for rearing larval bluegills Lepomis macrochirus in tanks. In preliminary experiments, seven commercial diets were fed to larval bluegills from the onset of exogenous feeding to 28 d posthatch. Although all diets were eaten by the larvae, none were observed to pass through the fish's digestive tract, and survival was essentially zero. In the next set of experiments, bluegill larvae survived on commercial diets when they were fed nauplii of brine shrimp Artemia franciscana for an initial 7-d period before being switched to commercial feed. Using this protocol, we compared three feeds (BioKyowa Fry Feed Kyowa B-250, Argent Hatchery Encapsulon Grade II, and Zeigler Larval AP-100) over a 28-d period. There were no significant (alpha = 0.05) differences in growth (length and weight) among fish fed the three diets at the end of 28 d, but survival was significantly higher for fish fed BioKyowa. In another experiment, we fed BioKyowa to larval bluegills after feeding them brine shrimp nauplii for 3, 7, or 14 d. Larvae fed brine shrimp for 14 d had significantly higher growth and survival than larvae in the other two treatments. Our results indicate that the feeding protocol for tank-rearing larval bluegills should start with brine shrimp before a commercial diet is used.
Observations of marks on channel catfish Ictalurus punctatus held for varying lengths of time in experimental ponds and on fish submitted for disease analysis suggested that aggressive biting among channel catfish may sometimes occur at relatively high rates in culture ponds. Studies in experimental pools indicated that larger fish sustained an average of 4 bites per fish while smaller fish sustained less than 1 bite per fish. Unfed catfish sustained an average of 12 bites per fish while fed fish sustained 7 bites per fish. No differences in the level of aggression were observed between genders. Mortality rates, apparently due to biting, ranged from 0% to 40% during the 2-4 week periods. Biting and subsequent infection of the wounds may contribute to the unexplained losses observed by producers.
Juvenile chinook salmon Oncorhynchus tshawytscha reared at Willamette Hatchery, Oakridge, Oregon, showed nonrandom distributions in both modified Burrows raceways and Michigan raceways. When fish were reared in Burrows raceways at densities of 10-15 kg/m(3), largest fish tended to reside near the upstream end of the raceway, but when fish were crowded for sampling, smaller fish were found at the upstream end, and larger fish were found at the downstream end. In Michigan raceways, fish near release size occupied six compartments formed by baffles. Smallest fish were usually found in the upstream and downstream compartments, while largest fish were in the middle compartments. Fish sizes were compared between fish sampled by dip net with and without crowding in all experimental raceways. Only 9 of 49 measurements showed statistical differences in weight between the two methods. We conclude that juvenile chinook salmon distribute in modified Burrows raceways and Michigan raceways in a nonrandom manner, even when crowded. For estimates of fish weights in hatchery raceways, care must be taken to sample all portions of the population to ensure that a nonbiased sample is obtained.
We evaluated the safety and effectiveness of chemical treatments for killing veliger and juvenile stages of the zebra mussel Dreissena polymorpha attached to unionid mussels. Static toxicity tests were conducted on eight unionid mussel species with common aquaculture chemicals (benzalkonium chloride, formalin, hydrogen peroxide, calcium chloride, potassium chloride, and sodium chloride). The concentration and duration of each chemical treatment tested had previously been found to kill zebra mussel veligers and juveniles. Several species (e.g., Elliptio dilatata, Lampsilis cardium, and Lasmigona complanata) incurred less than 10% mortality in chloride salt treatments, while in other species (e.g., Obliquaria reflexa and Leptodea fragilis) mortality varied greatly among treatment regimes. Treatments with benzalkonium chloride, formalin, and hydrogen peroxide were less than 90% effective on juvenile stages of zebra mussels and, therefore, were ruled out after preliminary trials. Limited application of specific chemical treatments may be feasible for more tolerant species; however, effective disinfection of unionid shells will require the use of chemical treatment followed by a quarantine period to completely remove zebra mussel larvae and juveniles.
Results and observations from 120 chloramine-T treatment trials to control mortality in a variety of salmonids caused by bacterial gill disease and columnaris are provided to aid fish culturists in determining more effective treatment regimes. When chloramine-T was used at 6, 10, or 15 mg/L, regardless of treatment frequency, efficacy in control of mortality was observed in 56%, 65%, and 61% of the trials, respectively. When chloramine-T was administered one, two, or three times, regardless of treatment concentration, efficacy was observed in 38%, 62%, and 88% of the trials, respectively.
The zebrafish or zebra danio Danio (=Brachydanio) rerio has recently become a major vertebrate model for the study of developmental biology, neurobiology, and molecular genetics. As a result, most research universities have now invested considerable resources in the construction of large zebrafish facilities. A key element in the design of these facilities is maximizing the efficiency of available space. Here we report on the effects of aquarium chamber volume on the reproduction of zebrafish, with the objective of identifying the minimal volume required for normal egg production. Six adults (two males and four females) were tested in chamber volumes of 500, 400, 300, 200, and 100 mL. Results were compared with those from a control volume of 3.5 L. Eggs were removed from the test chambers after spawning and incubated in petri dishes at 28 degrees C. Total egg production, percent of eggs hatching, and larval length at 96 h postfertilization were used to evaluate breeding success. Compared with the control, egg production was not significantly affected by reduced aquaria volumes of 500, 400, and 300 mi,. However, mean egg production from a test volume of 200 mt was only 48% of the control egg production (P < 0.05), and at a test volume of 100 mt, egg production was reduced to 26% of the control value (P < 0.005). Percent egg hatch and 96-h larval length were not affected at any test volume.
This is the first report on sperm cryopreservation for the cyprinid species asp Aspius aspius. Fish were captured from wild stock and kept under controlled conditions. Ovulation and spermiation were induced with hormonal treatment. Six simple carbohydrate-based extenders supplemented with 10% DMSO were tested for sperm cryopreservation. The most efficient extenders were 0.3 M sucrose, 0.6 M sucrose, and 0.3 M glucose. They resulted in survival to the eyed stage of 62 +/- 4%, 59 +/- 5%, and 49 +/- 4%. respectively, expressed as a percentage of control survival, which was 58 +/- 6%. The presence of chicken egg yolk in extenders significantly decreased cryopreservation success.
Florida largemouth bass Micropterus salmoides floridanus were tagged and placed into an indoor raceway to document time of spawning, duration of spawning episodes, number of fish contributing to spawns, number of fish spawning multiple times, and percent of fish that spawned. In 8 d of observation, 16 spawns were initiated from 1500 to 1850 hours (lights on at 0700 hours, off at 1900 hours), and 3 spawns occurred during the night. Spawning episodes lasted from 110 to more than 240 min. Two spawns included participation by more than one male or female, but in both cases, activity of the third fish was brief and did not appear to contribute gametes. Five males (25%) and three females (15%) spawned more than once, and multiple-spawning males always used the same nest. Fifty percent of the males and 65% of the females spawned at 10 mat locations during observations. Six mat locations were used after observations ceased, which added to the 10 confirmed locations and 2 mat sites from night spawns, indicating 90% male participation. Results indicated that the majority of spawning occurred during afternoon and evening hours and that males spawned multiple times using the same nest. Gamete contribution diversity appears to be adequate when raceway spawning is employed.
Sea-run cutthroat trout Oncorhynchus clarki were reared in and released from a pond with a gravel-earth bottom, a standard concrete raceway, and a raceway with baffles at the Cowlitz Trout Hatchery, Washington. Adult returns from two release years showed that significantly more fish from the rearing pond survived (3.2%) than fish reared in standard raceways (2.0%) and that significantly more fish returned from the standard raceway than from the baffled raceway (1.7%).
Photoperiod effects on fish are well known, but other aspects of light control for fish tanks, including light-shock reactions caused by abrupt on-off changes in lighting, have received less attention. This article provides a discussion of light control equipment—especially timing and dimming devices—available for fish tanks, lists information about some of the units that are commercially available in North America, and mentions some systems developed by fish culturists.
The 96-h median-lethal concentration (96-h LC50) of total ammonia nitrogen (ammonia-N) to fingerling shortnose sturgeon Acipenser brevirostrum was 149.8 +/- 55.20 mg/L (mean +/- SD, 17.9 +/- 0.62 degrees C, pH = 6.8-7.3). Calculated 96-h LC50 for un-ionized ammonia-N was 0.58 +/- 0.213 mg/L. The 96-h LC50 of nitrite nitrogen to shortnose sturgeon fingerlings was 11.3 +/- 8.17 mg/L (17.9 +/- 0.31 degrees C, <1.0 mg chloride/ L, <1.0 mg magnesium/L, 1.8 mg calcium/L, 7.7 mg sodium/L).
Four brood years of juvenile spring chinook salmon Oncorhynchus tshawytscha were reared in conventional and baffled raceways at various rearing densities and loads at Willamette Hatchery, Oregon. A period of rapid linear growth occurred from August to November, but there was little or no growth from November to March when the fish were released. Both fall and winter growth rates were inversely related to rearing density. Final weight and length were also inversely related to rearing density. No significant relationship between load and any growth variable was observed. Fish reared at lower densities in conventional raceways tended to develop bimodal length distributions in winter and early spring. Fish reared in conventional raceways showed significantly larger growth rates and final lengths and weights than those reared in baffled raceways. Food conversions and average delivery times for feed were significantly greater in baffled than in conventional raceways. No significant relationships were observed between either rearing density or load and condition factor, food conversion, or mortality. Mortality was not significantly different between the two raceway types. When fish were transported to seawater for further rearing, there were no significant relationships between mortality in seawater and rearing density or load, but fish reared in baffled raceways had significantly higher mortality than those reared in conventional raceways.
The thermal and light conditions for 2-year-old broodstock of yellow perch Perca flavescens were shifted by 6 months in an effort to change spawning from spring to autumn and fall. The natural photothermal conditions consisted of a chill period of 10 degrees C and 10 h of light during January-March followed by increases in temperature to 20-22 degrees C and photoperiod to 15 h light during July-September. The natural spawning of yellow perch occurs in April-May at 12-14 degrees C and 12 h light. In the present study, the broodstock were maintained at a higher temperature and a longer period of light during September-February (18 degrees C and 13 h light). The photothermal conditions were decreased gradually until June. The chill period (10 degrees C and 11 h light) was 60 d in duration (June-July) and was followed by gradually increased water temperature and longer daylight (12 degrees C and 19 h). Following this period, 50% of the females were fully ovulated, and they were stripped or spawned naturally. The males spermiated during the entire shifted spawning period, August-September. The average relative weight of ovulated eggs las a percentage of the female weight) was 26.6 +/- 10.7%. Embryo survival through the eyed stage was 56 +/- 24%. Larval skeleton abnormalities (45 +/- 15%) and a low frequency of swim bladder inflation (44 +/- 34%) were observed.
A float-stopper mechanism was designed to drain fish holding tanks directly from the bottom. Unlike traditional, top-drawn standpipe systems, it allows continuous flushing of settled solid waste. It also prevents the accumulation of these wastes between the two standpipes that are used in bottom-drawn, double-walled standpipe systems. When suspended solids are forced upward between the outer and inner standpipes of such systems, a minimum velocity must be maintained to prevent sediment accumulation. This minimum velocity determines the minimum flow rate through the tank. The system described in this report flushes well over a wide range of flow rates.
A 19-week study was conducted in Bahia Kino, Sonora, Mexico, to evaluate the effects of fertilization on growth, survival, food conversion ratio, and production of Pacific white shrimp Penaeus vannamei in earthen ponds. The contribution of phytoplankton, zooplankton, and benthos to shrimp food supply was assessed by examining changes in the abundance of these organisms in the ponds, as well as in shrimp gut content. Shrimp growth and biomass were higher in fertilized ponds, despite a lower feeding rate. These results suggest that fertilization enhances natural food and contributes to shrimp nutrition. Biota were more abundant in fertilized ponds. Guts of shrimp from fertilized ponds had significantly higher abundances of zooplankton and benthic organisms than guts of shrimp from unfertilized ponds.
Postrelease smelt survival of summer steelhead Oncorhynchus mykiss that had been trucked 0.75 h and released was compared with that of smelts that had been trucked and allowed to rest for 24 h before release. Results showed no difference in return rates, suggesting that resting after transport may not improve steelhead survival.
This experiment examined whether photoperiodic changes induce chinook salmon Oncorhynchus tshawytscha to alter various indices of smoltification. The effect of 24 h light, a constant photoperiod of 9 h light:15 h dark (9L:15D), and a naturally increasing photoperiod on plasma levels of thyroxine and cortisol, hematocrit, condition factor (K), and hepatosomatic index (HSI) was tested during the period of smoltification in chinook salmon. The 24-h-light group grew faster than the other two groups, but was significantly larger than one of the two groups on only three sampling dates. Mean plasma thyroxine and cortisol levels were highest in the natural-photoperiod group and lowest in the 9L:15D group. Mean plasma cortisol levels increased significantly in the increasing and 9L:15D photoperiod groups but were unchanged in the continuous-light group. Mean HSI decreased faster in the natural-photoperiod group than in the other two groups. Mean hematocrit did not change in the natural-photoperiod group but decreased in the other two groups. Mean K decreased in the natural-photoperiod and 24-h-light groups, but not in the 9L: 15D group. The natural-photoperiod group clearly showed a more coordinated and complete smoltification based on the indices measured: highest mean and peak levels of both thyroxine and cortisol, greatest decrease in HSI, greatest decrease in K (along with the 24-h-light group), and least decrease in hematocrit. These results show that a natural photoperiod is beneficial and that continuous light or a short, unchanging photoperiod are detrimental to smoltification in chinook salmon. Hatcheries should account for photoperiodic effects when raising chinook salmon, particularly indoors.
Adult sea-run Atlantic salmon Salmo salar captured and transported to Richard Cronin National Salmon Station (Sunderland, Massachusetts), Nashua National Fish Hatchery (Nashua, New Hampshire), and Whittemore State Fish Hatchery (Waterford, Connecticut) during 1986-1992 were treated with oxolinic acid and a bacterin. The bacterin was developed against furunculosis and enteric redmouth disease. Among the 2,552 fish that were treated since 1986, 362 died and 65 (18%) of those fish had furunculosis. Among 206 untreated fish that were maintained as controls, 109 died and 63 (57.8%) had furunculosis. The reduction in mortality could not be attributed to either vaccine or antibiotic alone without further study. A 3-year study was designed to investigate if adult Atlantic salmon, undergoing the stress of migration, handling, and spawning, could mount a protective humoral immune response. Although the salmon were able to produce an agglutinin response, evidence was not found for production of a protective humoral response by these vaccinated Atlantic salmon.
A modification of previously documented force-feeding procedures resulted in the renewal of appetite by several wild-caught juvenile Atlantic sturgeon Acipenser oxyrinchus. Four of four fish under controlled laboratory conditions responded positively to this technique within 1 month. These fish exhibited negative mean growth rates of -2.71 gld before force-feeding and gained an average of 2.61 g/d at 285 d after initiation of force-feeding. Mean lengths, weights, and coefficients of condition (K) also increased after force-feeding. This method may be useful in other situations in which the holding of juveniles or adults is necessary, such as in toes and public aquaria.
