Search

Acute morbidity and mortality of marlins (family Istiophoridae) in hook-and-line fisheries have been studied; however, there has been little or no investigation of the skeletal injuries incurred from terminal tackles that could lead to decreased rates of postrelease survival. The objective of this study was to evaluate skeletal injuries in recreationally angled Atlantic Blue Marlin Makaira nigricans from the 2019 Big Rock Blue Marlin Tournament in Morehead City, North Carolina. We examined heads of six Blue Marlin that were angled using artificial lures rigged with J-hooks and harvested for weigh-in. The head of each Blue Marlin was scanned using computed tomography (CT) and examined with gross dissection. The CT interpretation revealed that two Blue Marlin had minimally displaced fractures of the maxilla, one of which also had a fracture to the lachrymal bone. These radiographic lesions were associated with penetrating hook injuries. The CT images also revealed degenerative changes within the quadrate-articular joint in four Blue Marlin, which was associated with fish weight; the causes and consequences of these degenerative changes are unknown. Although the hooking-related jaw fractures likely result in acute pain, their impact on postrelease morbidity is unknown and the impact on postrelease mortality is suspected to be small.

A cylindrical micro acoustic transmitter (AT; weight in air = 0.2 g) has been developed for injection into the peritoneal cavity of fish. Laboratory studies can provide tagging guidelines to minimize the effects of implantation techniques and transmitter burden (transmitter weight expressed as a proportion of fish weight) before use of the AT in field studies. To establish guidelines for minimizing tagging effects, we examined response variables (mortality, transmitter expulsion, growth, and wound healing) for micro AT-injected juvenile Chinook Salmon Oncorhynchus tshawytscha over a wide range of sizes (65–104 mm FL). The overarching goal was to determine a minimum size threshold at which the adverse effects of micro AT injection on fish are minimized. Juveniles (n = 700) were separated into four treatments: (1) AT injection, (2) injection of an AT and a PIT tag (AT+PIT), (3) injection of visible implant elastomer (marked control), and (4) unmarked (true) control. Fish were evaluated once per week...

A length–weight relationship was developed for pond-raised hybrid catfish fingerlings, Ictalurus punctatus × Ictalurus furcatus. A total of 4663 fish were sampled ranging from 20 to 240 mm total length. Predicted weight (g) from length (mm) is based on the equation: Y = 0.000017311X2.868474309 (r2 = 0.996) where Y is the estimated individual fish weight and X is measured total length. The predicted values generated by this model differ from, but follow the same general trends seen with channel catfish, I. punctatus, fingerlings and can be used as a baseline for the development of a length–weight table for hybrid catfish fingerling production.

Hybrid catfish (♀ Channel Catfish Ictalurus punctatus × ♂ Blue Catfish I. furcatus) were reared as single-batch crops during the growing season (June–September) of two years under two different dissolved oxygen (DO) regimes each year: (1) a high-DO (control) treatment with minimum daily DO maintained above 3.8 ppm in both years and (2) a low-DO (test) treatment with minimum DO maintained at 1.6 ppm in the first year and 1.3 ppm in the second year. Fish were fed daily to apparent satiation with a 32% protein commercial feed and harvested each year. In both years, dissolved oxygen concentration significantly impacted gross and net production, final fish weight, and mean fish weight gain due to reduced feed intake. Feed intake was reduced in the low-DO treatment by 26.6% in year 1 and 29.2% in year 2. Food conversion ratios averaged 1.83 overall and were not affected by minimum DO. Fish in high-DO treatments gained an average of 44% more weight (1.50 lb/fish) than fish in low-DO treatments (1.04 lb/f...

Summary Larger meagre are more common in the market but, recently, smaller fish have started to be commercialised as well. This study aims to evaluate flesh quality and muscle cellularity of meagre of three different sizes: 800, 1500 and 2500 g. Results showed a higher fat content in larger fish (2.9% compared to 1.3% in small fish), and that texture was not affected by fish size. In terms of muscle cellularity, a higher frequency of smaller fibres was observed in 800 and 1500 g (33% compared to 18% in 2500 g) meagre, whereas in 2500 g meagre, there was a higher frequency of larger fibres. Muscle fibre density was reduced with fish weight (431 and 297 fibres mm−2 for 800 and 2500 g meagre, respectively). In conclusion, this study shows that meagre of different weights are different in terms of fat content and muscle cellularity and that 800 g meagre seems to have a good potential for being commercialised.

The continued expansion of intensive aquaculture activities requires that substitutes for fish meal-based protein be identified. In this study, we evaluated partial (50 and 75%) replacement of fish meal in red drum, Sciaenops ocellatus, diets with soy protein concentrate (S) and barley protein concentrate (B). Growth, feed efficiency, survival, tolerance to low temperature, and tolerance to handling in warm, hypersaline water were evaluated. Only the diet with a 50% replacement of fish meal with S yielded results comparable to fish fed a nonsubstituted fish meal diet. However, the low-temperature studies were complicated by differences in mean fish weight among the groups. The results of this study indicate S may be partially substituted for fish meal in red drum diets.

BACKGROUND This paper deals with the consequences of dietary restriction or complete starvation before slaughtering on the biochemical and textural characteristics of sea bass muscle. RESULTS Results showed that only severe feed restriction influenced negatively total body and individual organ weights, and these animals showed lower condition factor as well. Neither moderate feed restriction (up to 50% of the standard ration) kept for 30 days nor total starvation up to 12 days caused significant effects on fish weight and fillet yield. Muscle lipid content was lower in feed-restricted fish, although this parameter was not altered by starvation time. Differences between the two feeding strategies studied were observed in muscle textural and biochemical parameters, and the results point to an influence of the nutritional status on the post-mortem evolution of collagen and myofibrillar proteins, although firmness was not modified. CONCLUSIONS Moderate feed restriction prior to slaughtering could be advisable in sea bass culture, given that no detrimental effects on fish quality or fish performance were noticed, whereas substantial amounts of feed can be saved. © 2013 Society of Chemical Industry

Reports from hatcheries have demonstrated that commercially available diets are inadequate for June Suckers Chasmistes liorus and suggest that fish quality can be improved through species-specific diet optimization. To determine dietary protein and lipid levels for juvenile June Suckers, practical-type diets were formulated with 35, 40, or 45% protein and 8, 12, or 16% lipid and tested in a 3 × 3 factorial design. Two additional diets (45% protein and 16% lipid [45:16] without dicalcium phosphate supplementation and 45:16 with 2× dicalcium phosphate) were formulated to test the necessity of dicalcium phosphate supplementation. Each diet was fed to three replicate tanks (average initial fish weight ± SD = 4.48 ± 0.24 g) of fish per treatment (85 fish/tank); only duplicate tanks were used for the nondicalcium phosphate-supplemented treatment. Fish were reared in 80-L tanks supplied with 4 L/min of 22°C spring water and fed 6–4% body weight (BW)/d by automated belt feeders, 6 d/week. At the end of 1...

Summary This study tried to determine the protein and energy requirements of growing beluga sturgeon Huso huso using a factorial approach. The experiment was composed of four small-scale growth trails covering different weight ranges. The fish fed at 0, 20, 40, 60, 80 and 100% of satiation. DWG had a steady increase throughout the experiment following a non-linear equation as Y = 1.433 (±0.056) · Ln(X) )2.740 (±0.261); r 2 = 0.99, p < 0.001, where Y = weight gain (g/day) and X = fish weight (g). The daily requirement of digestible energy (DE) for maintenance amounted to 79.09 kJ · BW (kg) 0.8 . The daily requirement of DP for maintenance calculated as 0.93 g · BW (kg) 0.7 . The relationship between DE intake (X) and DE gain (Y) expressed as Y = )0.0004 (±0.000) X 2 + 0.600 (±0.082) X )44.95 (± 6.72). Also, the relationship between DP intake (X) and protein gain (Y) was expressed as Y= )0.019 (±0.006) X 2 + 0.548 (±0.062) X ) 0.498 (±0.121). The daily requirements of energy and protein were estimated as 79.09 kJ · BW (kg) 0.8 + 2.94 · DE gain and 0.93 g · BW (kg) 0.7 + 2.63 · DP gain. Apparently, beluga sturgeon is inefficient in converting energy and protein into body tissue. Therefore, energy content of the diet should be sufficiently high to satisfy large energy demands in beluga sturgeon and also to reduce the catabolism of protein.

Five commercial diets and two formulated feeds were fed to initial-feeding Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri fry and Snake River cutthroat trout O. clarkii spp. (currently being petitioned for classification as O. clarkii behnkei) fry for 18 weeks from June 16 to October 18, 2006, to evaluate fish performance. Eyed eggs from Yellowstone and Snake River cutthroat trout were received from the Yellowstone River State Fish Hatchery and Jackson National Fish Hatchery, respectively. Each diet was fed to four tanks of each subspecies of cutthroat trout (7 diets × 4 tanks/diet × 2 cutthroat trout subspecies = 56 tanks). Skretting Nutra-Plus provided optimal fish weight, total length, survival, and feed conversion for Yellowstone cutthroat trout. The weight and total length of Snake River cutthroat trout were also greatest when fish were fed Skretting Nutra-Plus. Skretting Nutra-Plus is no longer available, but Skretting/Bio-Oregon Bio-Vita is very similar; this feed and similar pr...

Lake trout, Salvelinus namaycush, were cultured in a series of five rearing units (in triplicate). The fish removed available oxygen in each unit, from about 10.5 to 7.0 mg/L. Oxygen was replaced, through aeration, between rearing units. Effects of cumulative loading, as fish weight/flow rate, are described in terms of water quality and fish growth. In fish reared at the highest loading level, mean growth during the 2-month cumulative loading period was depressed by more than half. However, the growth rate progressively increased in those fish reared under high loading levels, indicating acclimation of the fish to high metabolite concentrations. After two months of series-reuse rearing, cumulative loading was removed through introduction of fresh water (noreuse) to each unit, and fish recovery was monitored. During recovery, mean growth of fish that had been reared under the highest cumulative loading level was equal to or greater than that of fish that had been reared under the low loading levels.

Growth of selected crosses (P1♀ × F1♂, F1♀ × P1♂, and F1♀ × F1♂) of Lincoln University bluegill stocks were evaluated. The purpose was to test the commercial potential for reaching marketable size (227–340 g) within 2 years in an indoor water-recycle system and grow-out in ponds. Pond hatched young-of-year bluegill were reared in a 12-tank (719 L/tank) indoor water-recycle system. Fish were fed to satiation three times daily. Fish were weighed and measured for total length (TL), for a 120-d growth trial. Initial mean fish weight and TL were 28.0 ± 15.8 g and 106 ± 16 mm, respectively. Final mean weight was 119.4 ± 54.9 g, and mean TL was 161 ± 19 mm. Crosses were significantly different (P ≤ 0.05). Initial female weight averaged 82.1 ± 32.5 g, and male weight averaged 158.6 ± 45.5 g. Feed conversion ratio was 1.26, and survival was 99.4%. Specific growth rate (SGR) averaged 1.21%/d with a mean length increase of 0.5 mm/d. Fish were then marked by specific crosses with colored visible implant elas...

This study determined the effects of the minimum daily dissolved oxygen (DO) concentration on the production parameters of channel catfish Ictalurus punctatus in earthen ponds. Fifteen 1-acre ponds (five ponds per treatment) were managed as high-oxygen (minimum DO concentrations averaging 4.37 ppm or 54% air saturation from June through September), medium-oxygen (minimum DO concentrations averaging 2.68 ppm or 33.2% air saturation), or low-oxygen treatments (minimum DO concentrations averaging 2.32 ppm or 28.7% air saturation) using one 5-hp electric paddlewheel aerator per pond. Fish in the high-, medium-, and low-oxygen treatment ponds were fed a mean total of 14,008, 13,212, and 12,607 lb/acre of 28%-protein floating feed, respectively. Net production paralleled the total amount of feed fed, averaging 5,772, 5,278, and 5,113 lb/acre in the high-, medium-, and low-oxygen treatments, respectively. Individual fish weight at harvest also showed a similar trend, averaging 1.37, 1.33, and 1.30 lb in...

Anthropogenic modifications of rivers and estuarine habitats have reduced the growth and recruitment of shortnose sturgeon Acipenser brevirostrum throughout its native range. This study used data from laboratory experiments to examine the individual and interactive effects of salinity, temperature, and fish weight on the survival of young-of-year shortnose sturgeon. The shortnose sturgeon in these experiments ranged from 56 to 187 mm in total length, from 0.4 to 42.8 g in weight, and from 66 to 144 d posthatch in age. Survival in 23°C water declined as salinity increased, but salinity tolerance increased with body size. The salinity lethal to 50% of the test fish after 48 h ranged from 14.8‰ to 20.9‰. Survival in freshwater declined as temperature increased, but temperature tolerance increased with body size. The temperature lethal to 50% of the test fish after 48 h ranged from 28.2°C to 30.7°C. In factorial experiments, salinity and temperature interacted significantly to affect young-of-year su...

— The present study was conducted to evaluate production management methods to improve overall survival of channel catfish, Ictalurus punctatus, fry to the fingerling stage by incorporating the use of a live, attenuated vaccine against Edwardsiella ictaluri and employing an extended hatchery phase. In this experiment, four treatments were used. In Treatment 1, 10-d posthatch (PH) fry were vaccinated and then directly stocked into earthen ponds. In Treatments 2 and 3, 10-d PH fry were sham-vaccinated (control) and vaccinated, respectively, kept in nursery tanks for 22 d, and then stocked into earthen ponds. Fry in Treatment 4 were sham-vaccinated at 10 d PH, kept in nursery tanks for 22 d, and then vaccinated prior to stocking into earthen ponds. Mean fingerling yield at harvest ranged from 4716 kg/ha in Treatment 1 to 8112 kg/ha in Treatment 4. Mean individual fish weight ranged from 38.8 g in Treatment 1 to 40.9 g in Treatment 4, and feed conversion ratios (FCR) ranged from 1.15 in Treatment 4 to 1.51 in Treatment 1. Mean survival ranged from 47.5% in Treatment 1 to 73.4% in Treatment 4. In specific comparisons to evaluate the nursery effect (Treatments 1 and 3), yield and overall survival were significantly different (P 0.05) in yield, average weight, and FCR were observed between treatments. Results indicate that implementing an extended hatchery phase and vaccination strategy with older fry can improve overall survival of fingerling fish.

Almost 30 years after natural reproduction of Chinook salmon Oncorhynchus tshawytscha was discovered in Lake Ontario tributaries, little is known about the feeding dynamics of these fish after they enter the lake. This study assesses consumption by naturally produced age-0 Chinook salmon as they enter the nearshore region of Lake Ontario after emigrating from the Salmon River, New York, a major U.S. tributary of Lake Ontario. Evacuation rate, estimated as a function of temperature in controlled laboratory experiments, ranged from 0.214/h at 10°C to 0.352/h at 19°C. Diel field sampling for daily ration estimates occurred on three dates in late spring (June 6, 12, and 18, 2001). Although no consistent diel feeding pattern was observed, Chinook salmon maintained an elevated gut fullness value throughout the day and did not feed after dark. Moreover, daily rations (grams [dry weight] of ration per 100 g of dry fish weight), which ranged from 27.54 (SE = 3.07) on June 12 to 33.27 (3.7) on June 6, were...

We tested the hypothesis that the growth of fish exposed to high temperatures can be limited by available food energy whereas that of fish exposed to low temperatures can be limited by their metabolic capacity to exploit the available food energy. Under laboratory conditions we evaluated growth (%/d) and marginal metabolic scope (MMS; L·g−1·h−1) of juvenile red drum Sciaenops ocellatus exposed to two levels of dietary energy, low (LE; ∼4.1 kJ/g) and high (HE; ∼15.9 kJ/g), and to three temperatures, approximately 19, 25, and 29°C, for a period of 6 weeks. Growth rate and MMS increased with temperature, but only growth rate increased with dietary energy and then only at the higher two temperatures. The simulation model Ecophys. Fish was employed to elucidate experimental results potentially confounded by interactions between fish weight and the controlling effects of temperature on metabolism. The simulated and observed results both showed that performance is enhanced at higher temperatures, especi...

Temperature selection by white crappie Pomoxis annularis over 24 h was determined in two Missouri impoundments, Little Dixie Lake and Rocky Fork Lake, on six and five dates, respectively, during June-August 2001 using temperature-sensitive radio transmitters. Temperature and dissolved oxygen (DO) profiles showed that the habitable portions of the upper water columns associated with fish locations varied by as much as 6°C in temperature. The habitable portions of water columns were subdivided into three strata (warm, moderate, and cool) such that each stratum covered an equivalent temperature range (≤2°C). Discrete choice models (DCMs) were developed for each impoundment to predict the relative probabilities of white crappies selecting the different strata in response to stratum height, DO concentration, average temperature throughout the habitable water column (AVG), and fish weight. For each impoundment, a distinct DCM containing AVG as the sole predictor variable was most supported by the data....

Summary. Proposed developments of the Torry fish drying kiln have led to a need for a closer understanding of commercial fish drying processes. In order to investigate the effects on fish drying of air velocity, air temperature and humidity, and fish packing density, a mathematical model of the kiln has been proposed. This model establishes partial differential equations for fish weight, air temperature and humidity. the model is applicable to the drying of other materials. A solution is obtained numerically by standard finite difference techniques.

Steelhead Oncorhynchus mykiss support valuable sport fisheries in the Great Lakes but are largely sustained by stocking. In many Great Lakes tributaries, steelhead spawning and nursery habitats are limited by hydropower dams, and natural recruitment may be supplemented by habitats in adjacent coldwater creeks. In 1998–2001, we investigated the potential for natural production of steelhead in the Muskegon River, Michigan, a tributary to Lake Michigan, through analysis of parr diet categories, consumption, growth, survival, and production in the main-stem Muskegon River and in Bigelow Creek. We used electrofishing surveys to estimate parr growth and survival from changes in fish weight and density over time. We estimated diet from gut content analysis and consumption from bioenergetics model analysis. Average fall density of parr in Bigelow Creek was 20-fold higher than in the Muskegon River. Average summer daily mortality rate of parr in the Muskegon River was nearly threefold higher than in Bigel...

Purpose The aim of the present study was to investigate different characteristics of six Latanoprost generics. Methods Prize, drop size and volume in each generic were determined. The hardness of each bottle was further evaluated using a fish weight and a hook. Finally, pH was measured and the buffer capacity evaluated by addition of NaOH. Results Price, drop size and volume varied significantly between the brand version (xalatan) and the generic latanoprost products. Hence, drops sized were in the range 40–47 µl and the number of drops in each generic bottle varied between 95 and 111 drops. The embalages of each latanoprost product were different in both size and hardness. The control value of pH in the brand version (Xalatan) was 5.99 ± 0.01 (mean ± SD), whereas the generic latanoprost products had significantly higher values within the range 6.70–6.82. Hence, titration of 2.5 µl Xalatan to neutrality required 70.4 ± 0.4 nmol NaOH compared to the generic latanoprost products which required within the range 28.1–33.7 nmol NaOH. Conclusions The present study identifies differences among latanoprost generics such as different pH values and different buffer capacities. Moreover, the emballages varies significantly, thereby leading to critical variations in the handling of the generics. Finally, the number and size of drops in each generic were different, not to mention the prize variations between the brand version and the generics. Over all, generic eye drops should not be considered identical. Therefore, re-evaluation of the requirements for introducing generic drugs seems reasonable.

Overwinter growth of young-of-the-year (age-0) Atlantic salmon Salmo salar was studied during two winters in central New York streams. We hypothesized that longer and colder winters would negatively influence the growth of age-0 Atlantic salmon. Further, we predicted that Atlantic salmon growth and survival would be positively correlated with their size before the winter period. Four cages were placed in streams at three sites in the winters of 2000 and 2001, with six individually marked Atlantic salmon per cage. One cage was retrieved monthly at each site and the weight, length, and energy density of each fish were measured to calculate growth rate and condition factor. All fish survived the winter experiment irrespective of starting size. Mean energy density of fish at the conclusion of each experiment was positively related to fish weight at the start. Winter conditions were different between years, stream temperatures being colder in 2000 than in 2001 (overall winter mean [SD], 0.71°C [2.487°...

A subjective method was used to evaluate rigor mortis in 50 Gulf sturgeons distributed into 5 weight categories. Duration of rigor increased with fish weight. Onset of rigor ranged from 12 to 24 h. A new method to determine onset and resolution of rigor in cultured Gulf sturgeon was studied using analysis of video images. Insight on the progress of rigor through the fish body is provided. In 10 different time intervals from 0 to 67 h after death, fish were temporarily secured to the edge of a table by the head, with the body free to droop, and video images were taken. Rulers in the background allowed quantification of body position. The extent of deflection of various points along the body length was analyzed. New parameters based on maximum deflection and integral deflections were developed. Rigor in Gulf sturgeon took an average of 24 h to onset and 67 h to resolve and was not a uniform process: the tail reached maximum rigor later than the middle of the fish.

The golden shiner Notemigonus crysoleucas is the major species of baitfish raised and sold in the United States. They are shipped in trucks from large farms to distributors up to 2,500 km distant. The costs associated with shipping could be greatly reduced if truck loading were increased, but higher densities of fish elevate ammonia concentrations to detrimental levels. In our work, we have simulated live hauling conditions to measure the ammonia excretion rates of golden shiners at 15, 20, and 25°C. The experiments were conducted for 24 h in three recirculating systems after fingerling golden shiners were fasted and acclimated for 2 d. The experiment was repeated four times using different lots and sizes of golden shiners. The results indicated that there were no significant differences in the hourly ammonia excretion rates (HER) between two lots of same-size golden shiners. The hourly ammonia excretion rates were inversely proportional to fish weight and increased with temperature. The average ...

Parameters derived from laboratory experiments that separately measured the routine metabolic rates (respiration) and swimming speeds of young-of-the-year (age-0) alewives Alosa pseudoharengus were compared with values published for a bioenergetics model for adults. Respiration rates of age-0 alewives were significantly influenced by water temperature and scaled isometrically with weight (range, 0.0001–1 g). Swimming speed was strongly related to fish weight and, unlike for adult alewives, water temperature significantly influenced the swimming speeds of age-0 fish. Temperature coefficients, along with the slopes for the weight dependence of age-0 alewife respiration rates and swimming speeds, significantly differed by 51–709% from published parameters for adults. Using adult parameters, the standard respiration rates at 15–25°C of age-0 alewives weighing less than 0.02 g were overestimated by 7–88% and the swimming speeds for fish weighing less than 1.0 g were overestimated by 130–4,270%. Applic...

Four different methods of pelleting—extruded (EXT), steam pelleted (STM), using a Universal Pellet Cooker (UPC), and expanded (EXP)—were performed on subsamples of a single batch of mash to determine the effects on feed pellet characteristics, in vivo feed digestibility, and performance of rainbow trout Oncorhynchus mykiss fed the diets for 16 wk. Results indicated that the STM feed was the most (851 g/L) and UPC feed the least (672 g/L) dense, and that UPC feed had the highest % float (8.3%) and, of the pellets that sank, the fastest sink rate (15.1 cm/sec). While some differences occurred among pelleted diets in loss of dry matter (% dry loss) after incubation in a water bath for up to 10 min, the overall % dry loss was only approximately 1–2%. The method of pelleting did not affect fish weight gain, feed conversion ratio, or specific growth rate. Measurement of the apparent digestibility coefficient of dry matter of the test diets using Cr2O3 as the marker ranged from 71–89%. While it appeared that the method of pelleting can affect feed characteristics and the amount of feed offered to the fish, fish performance was not affected.

To increase commercial marine catches of masu salmon Oncorhynchus masou in northern Japan, hatchery-reared juveniles are stocked at several life stages. To minimize mortality from freshwater angling, fish are often stocked in the fall when the fishing season is almost finished. In the fall of 1994–1998, we experimentally stocked hatchery-reared age-0 masu salmon (mean weights, 4.1–13.9 g) in the Masuhoro River of northern Japan. Mark–recapture experiments were conducted to estimate the numbers of hatchery-origin masu salmon smolts in the spring. Numbers of masu salmon parr in the river were estimated in July 1998–1999 when the smolt runs were almost finished. The proportion of fish smolting at age 1 (2.2–15.7%) was positively correlated with mean weight at release. Overwinter survival (9.0–17.0%) was also correlated with fish weight at release. Our study showed that size at release is an important factor when stocking age-0 masu salmon in the fall to maximize the number of smolts produced and the...

We studied the initial mortality of black bass Micropterus spp. that were captured, weighed in, and released in fishing tournaments conducted by the Bass Anglers Sportsman Society between 1972 and 1998. Mean annual initial mortality (i.e., mortality be- fore weigh-in and release) ranged from 1% to 30%. Ini- tial mortality was greatest during the 1970s (15.2%) and decreased during the 1980s (5.7%) and 1990s (1.9%). Because initial mortality was uniformly low ( #5%) after 1982, we used results for 1983-1998 to assess relation- ships involving initial mortality. Initial mortality was correlated with bag size, mean fish weight per angler, and number of fish per angler. Logistic regression showed that these three variables and their interactions explained significant portions of the variation in black bass initial mortality. Our results suggest that the initial survival of black bass caught in tournaments can be improved by reducing the number or total weight of fish that anglers can hold in their live wells during the day. This could be accomplished by decreasing tournament bag limits.

Atlantic Salmon, Salmo salar L., experimentallyinfected with marine Eubothrium sp. were kepttogether with uninfected salmon in the laboratoryfor 11 months in two tanks, 80 infected and 80uninfected in each tank. The infected fish had areduced growth rate compared with the uninfectedfish. Significant differences in growth betweeninfected and uninfected fish were not observeduntil several months post-infection. There was nocorrelation between the number of Eubothrium sp.and fish weight, indicating that even low intensityalters the growth rate of the salmon. The cestodehad the same effect on both sexes of salmon.Haematocrit level was found to be significantlylower in infected compared with uninfected salmonin one of the samples during the experiment.Keywords: Eubothrium, Atlantic salmon, cestodes

The optimal dosage of astaxanthin for goldfish Carassius auratus was determined by feeding a series of diets containing 0, 25, 50, 75, and 100 mg of astaxanthin/kg of diet for 4 wk. The pigmentation on fish skin was measured by visual assessment against a color chart and by counting chromatophores produced in the dermis layer of fish skin. Both criteria showed that 36–37 mg/kg astaxanthin was the optimal dosage to stimulate fish color. A 4-wk observation after this experiment demonstrated that fish color stimulated by dietary astaxanthin was stable in its intensity. Therefore feeding astaxanthin could be a suitable way for goldfish producers to stimulate color among fish grown in an algae-free environment. The survival rate of fish fed diets with astaxanthin was significantly higher than fish fed diets without astaxanthin. However, there was no significant effect of astaxanthin on fish weight gain.

Residues—including heads, skin, viscera, frames, and trimmings—from the channel catfish Ictalurus punctatus processing industry have generally been made into catfish meal and catfish oil that are used in animal feeds. There may be more efficient uses for these materials, such as producing collagen and other products. A study was conducted to determine the percentages of each component of the processing residue relative to whole fish weight and their crude protein, crude fat, moisture, ash, and collagen concentrations. Of a market-size channel catfish, the head accounted for 24% of the whole weight, the frame 13.6%, the viscera 10.8%, the skin 4.7%, and the trimmings 3.7%. These processing residues represent a total of 56.8% of the total fish weight. The highest crude protein and collagen concentrations were found in the skin (protein, 19.9% of wet tissue and 82.1% of dry matter; collagen, 14.2% of wet tissue and 58.7% of dry matter). The viscera had the highest fat level (32.7% of wet tissue and ...

We tested bioenergetics model predictions of fish growth and food consumption under feeding regimes that elicited compensatory growth (CG) responses and for control fish fed ad libitum daily. Three treatment groups of seven juvenile hybrid sunfish (F1 hybrid of female green sunfish Lepomis cyanellus × male bluegill L. macrochirus) received repeating cycles of no feeding and refeeding; fixed no-feed periods of either 2, 4, or 14 d distinguished the treatment groups. The no-feed periods induced CG and were immediately followed by days of ad libitum refeeding. The refeeding periods for each treatment group were continued until the group's mean daily consumption no longer exceeded that of the controls, after which another no-feed period began. Bioenergetics model predictions of cumulative consumption and fish weight in 105-d experiments were not significantly different from observed values in the control group (2–3% model error). However, the model underestimated cumulative consumption (18–25%) and o...

At different heart rates, the conduction time through the atrium of gilthead sea bream Sparus auratus (P-R interval) was constant in each fish but differed from one fish to another. This difference was not related to the body size of the animal, suggesting the lack of preferential conduction pathways in the atrium. A clear relation between R-T interval and fish weight was observed, suggesting a similar conduction speed of the excitatory wave and the presence of specialized conductive tissue in the ventricle. Moreover, the P-R and R-T intervals did not participate in the determination of the heart rate, and all changes in the heart rate were related to changes in the T-P interval.

We investigated the effects of prey availability on relative weights (Wr ; the ratio of fish weight to the weight of a standard fish of the same length) in populations of walleye Stizostedion vitreum from two reservoirs, Lake Ogallala and Lake McConaughy, in western Nebraska. Partitioned by season of capture and 50-mm length-classes, walleye Wr was compared with the abundance of prey fish by length-class. Walleye Wr changed seasonally and was heavily influenced by prey size availability. In Lake Ogallala, where smaller prey were abundant, there was no significant difference in Wr across length-classes by fall. In Lake McConaughy, where more than 90% of all prey fish were over 170 mm, there was a distinct trend by fall. Small walleyes (250–400 mm) exhibited the lowest Wr (92.0 ± 0.84); and large walleyes (550–700 mm) had the highest Wr (104.0 ± 1.57). Examining changes in walleye Wr among length-classes across seasons was more informative than using a mean population Wr because it was sensitive to...

Sectioned sagittal otoliths were used to determine ages of vermilion snapper Rhomboplites aurorubens collected from the South Atlantic Bight (SAB) by trawl, trap, and hook-and-line gear during 1979–1993. Annulus formation, validated by marginal increment analysis of ages 1–8, occurred from June to August, the peak spawning period for vermilion snapper. Ages ranged from 0 to 12 years for each sex. No significant difference was found for size at age between males and females. The von Bertalanffy growth equation for vermilion snapper taken during 1979–1981 was TL t = 562{1 – exp[–0.202(t + 0.117)]}, where TL t = total length (mm) at age and t = age in years. The length–weight relationship was w = 2.147 × 10−5 TL2.899, where w = whole fish weight in grams. Weighted mean back-calculated lengths at age, compared by analysis of variance for five 3-year periods, declined from 1979–1981 through 1982–1984 to 1985–1987. but did not change significantly during 1985–1993. The temporal decrease in size at age ...

We studied the use of compensatory growth (CG) to grow fish larger than control fish that were fed every day without restriction. Five treatment groups of 10 juvenile hybrid sunfish (F1 hybrid of female green sunfish Lepomis cyanellus × male bluegill L. niacrochirus) received repeating cycles of no feeding and refeeding; fixed no-feed periods of either 2, 4, 6, 10, or 14 d distinguished the treatment groups. No-feed periods elicited the CG state and were immediately followed by days of ad libitum refeeding. Refeeding periods within each treatment group (D2, D4, D6, D 10, or D14) were continued until mean daily food consumption by fish no longer exceeded that of controls fed ad libitum every day (i.e., ad libitum refeeding was continued for as long as hyperphagia persisted, then another no-feed period began). Fish in two groups, D2 and D 14, consumed more food and significantly outgrew controls by 2 and 1.4 times, respectively, in 105-d experiments. Gross growth efficiency (GGE, fish weight gained...

The range of splittail Pogonichthys macrolepidotus has decreased to less than a third of its original range due to loss or alteration of habitats. We measured the critical thermal minima (CTmin) and maxima (CTmax), critical dissolved oxygen minima (CDOmin), critical salinity maxima (CTmax), salinity endurance, and critical swimming velocity (U crit) for age-0 (0.1–4.0 g), age-1 (10–48 g), and immature age-2 (72–201 g) splittails to assist in effective water and habitat management and restoration of this species. Neither thermal acclimation nor fish weight affected the CTmin (6.5–7.3°C), but CTmax (29–33°C) of fish acclimated at 17 and 20°C were higher than CTmax (21–22°C) of fish acclimated at l2°C. Mean CDOmin values were low (0.6–1.3 mg O2/L) for all age-groups, although immature age-2 fish acclimated at 12°C had a lower CDOmin than any group acclimated at 17°C. Mean CTmax (20–29‰) did not vary with acclimation temperature, but increased with increasing weight for fish acclimated at 17°C. Mean ...

Because the mass-specific power generated by myotomal muscle during swimming varies along the length of the fish, a realistic assessment of total power generation by the musculature requires integrating the product of mass-specific power and muscle mass at each position over the length of the fish. As a first step toward this goal, we examined the distribution of red, pink, and white muscle along the length of Stenotomus chrysops (scup) using histochemical and image analysis techniques. The largest cross-sectional area of red fibers occurs at 60% of total fish length and declines both anteriorly and posteriorly. By contrast, white fibers have the largest cross-sectional area in the anterior and decline dramatically moving posteriorly. The proportion of the fishes' cross-section occupied by red fibers increases from 1.37% to 8.42% moving posteriorly along the length of the fish. In contrast, the proportion of cross-sectional area occupied by pink fibers is constant (1.19%), while the proportional cross-sectional area of white fibers falls from 82.5% to 66.3%. The red, pink, and white fibers comprise 2.09, 0.73, and 51.1%, respectively, of total fish weight. We also compared the distribution of muscle in 10 degrees C- and 20 degrees C- acclimated animals. The value for red fiber volume, though slightly higher (13%) in cold-acclimated fish, is not statistically different. No difference was found in pink or white fibers. Finally, the finding that most of the red muscle is in the posterior half of the fish further supports the notion that most power for steady swimming at moderate speeds comes from posterior rather than anterior musculature.

Laterally compressed panfishes are small and have limited intraperitoneal space; thus, they may suffer adversely from surgically implanted transmitters even if the transmitter meets the generally recommended ratio of transmitter weight to fish weight of 2%. We studied the effects of intraperitoneal transmitters (2.81 g) on survival, growth, healing, and health of bluegills Lepomis macrochirus (mean weight 133 g) held for 8 weeks at 6°C and 20°C. Radio-tagged bluegills at 20°C had a mortality rate of 10% and tag loss rate of 15%. At 6°C, bluegills had no mortality or tag loss. Radio-tagged and reference fish fed in both 20°C raceways; however, a few reference fish appeared dominant at feeding time. This dominance by a few reference fish was also indicated by a large weight gain for three reference fish in each 20°C raceway. At 6°C, neither reference fish nor radio-tagged fish fed activity. Radio-tagged fish held at 20°C exhibited pelvic fin erosion, erythema and necrosis at the antenna exit and at...

Three oilseed protein concentrates (soybean, canola, and sunflower) were evaluated to determine their potential, when supplemented with deficient essential amino acids, to partially or completely replace fish meal in diets fed to rainbow trout Oncorhynchus mykiss. Triplicate aquaria of juvenile trout (average weight of 12 g) were fed the experimental diets for 10 wk, at which time the average weight of the fish was approximately sixfold higher than the initial weight. Average fish weight gains on diets in which the protein component was 100% fish meal; 75% fish meal, 25% soybean protein concentrate; 50% fish meal, 50% soybean protein concentrate; and 75% fish meal, 25% sunflowerseed protein concentrate were not significantly different (P < 0.05). The average weight of fish fed a commercial feed was significantly lower than that of fish fed the 100% fish meal diet, but not significantly different from fish fed the three other formulations mentioned above. Fish fed diets containing 50% fish meal, 50% canola protein concentrate; and 25% fish meal, 75% sunflowerseed protein concentrate had significantly lower average final weights than those of fish fed the other diets. Feed conversion ratio patterns among the dietary treatment groups reflected those of weight gain. Fish survival exceeded 95% on all diets. Apparent protein digestibility coefficients ranged from 79.5% (75% soybean protein concentrate, 25% canola protein concentrate) to 90.6% (100% soybean protein concentrate). The results of this study demonstrated that certain oilseed protein concentrates have good potential as protein sources in rainbow trout feeds when properly supplemented with essential amino acids.

We described and compared population structure, growth, mortality, and reproduction of northern Squawfish Ptychocheilus oregonensis among four reservoirs of the lower Columbia River and among four reservoirs of the lower Snake River. We also pooled data for comparisons among three larger areas: Columbia River reservoirs, Snake River reservoirs, and the unimpounded Columbia River downstream from Bonneville Dam. Females made up 76–100% of northern squawfish 380 mm fork length or greater in individual reservoirs, and 87–99% of fish 380 mm or greater in the three combined areas. Females lived longer and grew faster than males in all reservoirs and areas and had lower annual mortality rates in all but two reservoirs. Proportional stock density was highest and annual mortality rates were generally lowest in Columbia River reservoirs. Northern Squawfish downstream from Bonneville Dam had a lower mean relative weight and higher relative fecundity (eggs per unit fish weight) than populations in impoundmen...

Food consumption and growth rates of 7–28-day-old Menidia beryllina were measured in response to natural ranges of temperature and prey availability. Feeding level, temperature and age all had significant effects on growth rate, although the effect of feeding level explained most of the variance. Feeding level also had a significant effect on gross growth efficiency, but temperature and age did not. Absolute growth rates (mg per day) increased dramatically with temperature, feeding level, and age. Variability in growth was greatest for fish feeding at the lowest feeding level. For a given fish weight, temperature had a positive effect on consumption rate, and maximum consumption (Cmax) of any treatment combination reached 75% body weight per day. Maximum growth rate was estimated at 24.6% body weight per day, and gross growth efficiency reached an estimated maximum of 0.375 at an ingestion rate of 25% body weight per day. Starved larvae lost on average 5.4% body weight per day and larvae required 6.4% body weight food consumption per day for maintenance. Multiple regressions of feeding level, temperature, and age/size on instantaneous growth rates indicated that increases in temperature increased maintenance requirements and required that fish consume a greater proportion of Cmax to attain maximum growth. Growth rates decreased with increases in temperature for fish eating a specific weight of food.

Five hundred and four stone loach 63–202 mm in total length, of I + to 8 + age groups, were sampled in two rivers of East Siberia from April to October 1989–90. This paper presents data on the seasonal dynamics of fecundity, ripening, fatness and feeding intensity. A second spawning from the end of August to October has been identified for the first time for this species. The absolute fecundity ranged from 1710 to 27600, and the relative fecundity varied from 216 to 833 eggs g−1: (fish weight). Stone loach in the River Olkha grew faster than those in the River Goloustnaya and, according to this index, are closer to stone loach from streams of northern England.

We tested the hypothesis that the energetics of swimming in a flume accurately represent the costs of various spontaneous movements using empirical relationships between fish swimming costs, weight, and speed for three swimming patterns: (1) ‘forced swimming’ corresponded to movements adopted by fish forced to swim against a unidirectional current of constant velocity; (2) ‘directed swimming’ was defined as quasi-rectilinear movements executed at relatively constant speeds in a stationary body of water and (3) ‘routine swimming’ was characterized by marked changes in swimming direction and speed. Weight and speed explained between 76% (routine swimming) and 80% (forced swimming) of net swimming cost variability. Net costs associated with different swimming patterns were compared using ratios of model predictions (swimming cost ratio; SCR) for various weight and speed combinations. Routine swimming was the most expensive swimming pattern (SCR for routine and forced swimming =6.4 to 14.0) followed by directed (SCR for directed and forced swimming =0.9 to 2.8), and forced swimming. The magnitude of the difference between the net costs of forced and spontaneous swimming increases with movement complexity and decreases as fish weight increases.

Two different commercial vaccines against furunculosis, caused by Aeromonas salmonicida subsp. salmonicida, were tested in Atlantic salmon on seven fish farms. Both vaccines were based on formalin-inaclivated bacterins containing aluminium salts as adjuvants. The fish were vaccinated by intraperitoneal injection in the spring approximately one month prior to transfer to sea water, and they were challenged by natural outbreaks of furunculosis. During the first year, six of the farms experienced disease outbreaks. The overall mortality was 7·14% in vaccinated fish and 21·7% in unvaccinated controls, giving a relative percentage survival (RPS) of 67%. In the seventh farm, outbreaks of furunculosis more than one year after vaccination revealed that there was still a trend towards lower mortality in vaccinated fish, though the mean RPS fell to 22%. The use of adjuvants in the vaccines resulted in local lesions in the abdominal cavity of vaccinated fish. However, the severity of the lesions declined gradually, and they did not influence fish quality at the time of slaughtering. Vaccination also had a moderately adverse impact on fish weight gain in most cases.

Channel catfish were fed five diets containing 24, 28, 32, 36 or 40% protein in intensively stocked earthen ponds over a 141 d growing season. Mean standing crop at harvest was 7,559 kg/ha, and maximum daily feed allowance was 105 kg/ha. Dietary protein concentration had a negative linear effect on weight gain. Total ammonia-nitrogen (TAN) in pond water increased linearly as dietary protein concentration increased and was positively correlated with total protein fed. However, unionized ammonia-nitrogen (NH3-N) was not influenced by dietary protein concentration. Dietary protein had a positive linear effect on nitrite-nitrogen (NO1-- -N) concentration, which was positively correlated with total protein fed and TAN. There was no significant correlation between NO2---N and fish weight gain, although there was a significant positive correlation between NO2-- -N/Cl-molar ratio in pond water and concentration of methemoglobin in the fish. Results from this study indicate that when the feeding rate is as high as 100 kg/ha/d, or 3,000 kg protein/ha/season, dietary protein concentrations of 36% and above can result in harmful concentrations of NO2---N when Cl concentration in the ponds is 2–3 mg/L. Although the NO2---N/Cl- ratio in the ponds increased to harmful levels with protein concentration of the diets, this might not be the major cause of the reduction in fish growth rate as dietary protein increased because the greatest difference in weight gain occurred at the lower protein concentrations and the greatest difference in NO2---N occurred at the higher dietary protein concentrations.

The statistical treatment of condition used in many previous studies has been to determine a predicted weight for a fish, and to calculate a ratio of actual to predicted weight. The ratios obtained, known as condition factor K, are then further analysed using analysis of variance or other techniques to relate changes in K to other independent variables. It is suggested that condition can be studied better by using a single model to analyse the response of fish weight to a number of factors simultaneously. This approach affords benefit from the simplicity of using an integrated analysis and avoids problems with skewed distributions of ratios. An example using data on the Pacific sardine, Sardinops sagax (Jenyns), is given. Changes in condition of this fish due to monthly, yearly and temperature effects are calculated.

We evaluated a large data set and confirmed that current standard weight (Ws ) equations for white crappies Pomoxis annularis and black crappies P. nigromaculatus are length-biased. We applied the regression-line-percentile (RLP) technique to length-weight data for 27,002 white crappies (175 populations) and 21,709 black crappies (80 populations) to develop new 75th-percentile Ws relationships. The proposed Ws equations are log10 Ws (g) = –5.642 + 3.332 log10TL(mm) for white crappies and log10 Ws (g) = –5.618+ 3.345 log10TL(mm) for black crappies; TL is total length. There was no systematic bias evident in Wr values (Wr = 100· W /Ws ; W is individual fish weight) calculated with the RLP-generated equations. Frequency distributions of population-mean Wr values were consistent with those from studies of other fish species. No regional trends in Wr were observed. Moderate correlations were found between Wr and population structure. Relative weight was generally highest in the spring, decreased after...

Production characteristics of pan-size (approximately 227 g) channel catfish (Ictalurus puncturus) were determined in cages and open ponds stocked with fingerlings to densities of 20,000 and 12,500 fish/ha. After 145 days, mean fish weight in all treatments exceeded 227 g. Mean survival was similar in all treatments. Food conversion ratios were significantly better in ponds than in cages but density did not affect the ratios. Neither density nor production system affected production (as measured by total weight produced) when initial density differences were considered (analysis of covariance). Variability in total length at harvest was similar between production systems; however, low density treatments were less variable than high density treatments. Results of this study indicate that pan-size channel catfish can be cultured efficiently at stocking densities well above the 12,500 fish/ha (5,000 fishlacre) generally used when culturing fish to larger sizes.

Functional relationships were derived in order to describe the effects of fish weight (262–2066 g), temperature (1–14° C), prey size and ration size (0.4–8.4% body weight) on gastric evacuation in cod fed four natural prey types. Interindividual (unexplained) differences among voluntary fed cod were relatively large. Power functions were appropriate for describing the effects of fish weight and ration size on the half-time of evacuation. Effects of meal and/or prey size appeared to counterbalance the effects of cod size. It is suggested that when cod of different sizes are fed fixed proportions of their body weight evacuation time is constant and independent of body size. There was found to be an exponential relationship between temperature and gastric evacuation time but, observations made at similar temperatures at different times of the year suggested that seasonal effects were of minor importance.