Fish Average Weight Research Articles

Effects of Feeding Frequency and Ration Level on Growth Performance and Non-Specific Immunity of Juvenile Turbot (Scophthalmus maximus) at Different Growth Stages

Four growth trials were carried out to optimize a feeding regime for turbot in industrial aquaculture systems at 15±0.5°C. Six ration levels (50%, 60%, 70%, 80%, 90%, and 100%) of satiation were tested in trial I and five ration levels (60%, 70%, 80%, 90% and 100%) of satiation were tested in trial III. For optimal feeding frequency, turbot were fed to satiation for 1 meal/day, 2 meals/day, 3 meals/day in trial II, and 1 meal every other day, 1 meal/day, and 2 meals/day in trial IV. The average initial body weight of fish was 28.90±0.07g for trials I & II, and 181.75±1.05g for trials III & IV. Growth performance generally decreased and feed utilization increased with decreasing ration levels, while no significant differences were observed with small sized turbot fed to 80%, 90%, 100% levels of satiation, and with large sized turbot fed to 90% & 100% levels of satiation. There was no increase in size heterogeneity with decreasing ration levels. Ration levels significantly influenced water quality. There were no significant differences in growth and feed efficiency among turbot fed with different feeding frequencies. Feeding small size turbot once a day and large size turbot once every other day at a ration level of 80% satiation is suggested for better feed utilization and less waste output.

Effect of Algae Based Diets on Growth Performance, Body Composition and Fatty Acid Profile of Indian Major Carp, Rohu Labeo Rohita, Hamilton)

Six iso-energetic (352 kcal gross energy/100 g feed) and iso-nitrogenous (32% crude protein) experimental diets containing one of the four algae (Anabaena cylindrica, AN; Nostoc salbasa, NS; Spirulina platensis, SP; Westleopsis prolifica, WS) as the major dietary ingredient (40% of the total composition) or algal meal mixture with supplemental protein (AMM+PS) or only algal meal mixture (AMM) were tested against a control diet to find out the suitability of algal meal to develop practical diet for rohu fingerling. The experimental fish of average weight 2.0 ± 0.1 g were fed at a rate equaling 4% of body wt/day for 8 weeks at an experimental temperature of 28 ± 2°C. Significant (p<0.05) enhancement in growth rate was observed in the groups fed with WS (571%) followed by the groups fed with NS (517.6%) and SP (502.8%) as compared to that of the groundnut oil, rice bran and soybean meal based control diet (406.4%). Fingerlings fed with algal meal mixture (AMM) gained least (255.2%). Diet with WS performed well in terms of FCR, PER, HSI, MR and CF when AMM showed least efficiency. Fish fed with SP showed better protein utilization (ANPU%) as compared to the other dietary groups. Carcass protein was not affected by any diet. The MUFA and PUFA of liver and PUFA of muscle increased over the initial value fed with control and experimental diets. But the MUFA of muscle with these diets are less than the initial. The SFA content in all diets of both the tissues is either same or less than initial value except with AMM diet. The total n-3PUFA in liver increased with all diets over the initial value. But this increase in muscle was observed only with AN, NS, WS and AMM+PS diets. The n-6PUFA of liver and muscle remained either same or increased with all diets over initial value. This study showed that individual algal diets gave better result in growth performance and PUFA content. Among all the algal diets WS found to be the best.

Evaluation of the growth performance of fishes in industrial waste fed ponds under Rajshahi City Corporation

Growth performance of fishes was evaluated for a period of six months (May to October, 2007) in industrial waste fed ponds located at Rajshahi City under three different treatments of species variation namely Tl (Labeo rohita, Catla catla, Cirrhinus mrigala, Hypophthalmichthys molitrix, Cyprinus carpio) in non waste pond, T2 (L. rohita, C. catla, C. mrigala, H. molitrix, C. carpio, Labeo bata) in industrial waste fed pond and T3 (L. rohita, C. catla, C. mrigala, H. molitrix, C. carpio, L. bata, Oreochromis nilotica) in waste fed pond. All the treatments were replicated twice. Stocking density 14,000 individuals/ha was same for all the treatments. The average initial weight of fish was 28.9g. Treatments had no significant effect on the mean SGR and survival rate of fishes except C. carpio. Mean SGR (%, bwd-1), weight gain (g), final weight (g) and survival rate (%) varied from 1.14±0.26 (T2) to 1.67±0.44 (T1), 34.00±2.81 (T2), to 114.22±12.37 (T1), 235.75±2.59 (T3) to 752.50±4.50 (T1), 60.50±4.50 (T3) to 82.50±2.50% (T2), respectively. Total fish yield (Kg/ha) significantly (P&lt;0.05) varied from 2234.50±24.40 (T2), to 2532.50±1.50 (T1). Mean water temperature [(27.73±0.50 (T1) to 28.09±0.53°C (T2)], dissolved oxygen [(4.45±0.18 (T3) to 6.00±0.22 mg/l (T2)], pH (7.73±0.11 (T1) to 8.32±0.15 (T3)], ammonia-nitrogen [(0.0069±0.0018 (T1) to 0.039±0.0029 mg/1 (T3)] and total alkalinity (95.09±3.22 (T1) to 160.49±18.97 mg/I (T2) significantly (P&lt;0.05) varied under the different treatments.&#x0D; Asian Australas. J. Biosci. Biotechnol. 2016, 1 (3), 492-503

Enhancement of quality of rainbow trout (Oncorhynchus mykiss) flesh incorporating barley on diet without negative effect on rearing parameters

Barley concentrations ranging from 0 to 32% (0B, 40B, 80B, 160B, and 319B) were incorporated into rainbow trout, Oncorhynchus mykiss (Walbaum) diets. The experiment started with an initial average fish weight of 127.72 ± 5.65 g and finished when they reached commercial weight (final weight between 312 and 330 g) after 84 days. The inclusion of barley in the diets did not show a significant effect on growth and biometric parameters, fat and carbohydrate digestibilities; however, protein digestibility decreased significantly with the incorporation of barley on diets. Glucose levels increased significantly with barley concentration in the diet, and lactate and cortisol levels were also significantly affected after a stress period regardless of the diet. Meat quality was influenced as well by barley concentration. Lower water activity values and an enhancement in textural and color properties were observed in fish fed with the diet containing the highest barley concentration. Trout fed feed with higher concentrations of barley (160B) showed lower lipid oxidation levels than those fed with lower concentrations (control and 40B). The sensory panel found that fish fed with diets higher than 8% in barley content (80B) exhibited a brighter red color in the gills and a better texture; also, meat color became redder with a higher barley inclusion (160B and 319B), being all these sensory parameters correlated with fish freshness. Thus, results indicate that barley can be substituted for wheat fraction without any detrimental effect on production efficiency and enhancing fish quality.

Effects of Varying Levels of High‐Protein Distiller's Grains on Growth Performance of Channel Catfish, Ictalurus punctatus, and Post‐Extrusion Feed Pellet Characteristics

AbstractChannel catfish, Ictalurus punctatus, remains the USA's largest aquaculture industry. However, in recent years, high feed prices have negatively impacted profitability. Production of ethanol as a biofuel has increased dramatically. Companies have modified their processes to enhance ethanol yield and these modified processes also increase the crude protein content of the byproduct. The object of this study was to evaluate this high‐protein dried distiller's grains (HP‐DDG) for its suitability in catfish diets. A total of 25 full‐sibling channel catfish (7.1 ± 2.3 g) were randomly stocked into each of twelve 260‐L polyethylene tanks to achieve 25 fish per tank. The control diet was similar to a commercial formulation. Experimental diets contained 20, 40, or 40% HP‐DDG with added lysine (1% of total diet). There were three replicate tanks per diet. Fish were fed to apparent satiation twice daily for 9 wk. Average harvest weights for fish fed the 40% HP‐DDG diet without lysine supplementation (57.0 g) were significantly smaller than that for fish fed the control diet (77.7 g). Average harvest weights of fish fed 20% HP‐DDG (86.8 g) were significantly greater than that of fish fed either 40% HP‐DDG (57.0 g) or 40% HP‐DDG + lysine (73.7 g). There were no significant differences in feed conversion ratios or survivals among treatments, which overall averaged 1.1 and 99%, respectively. These data indicate that HP‐DDG appears to be a suitable ingredient in channel catfish diets up to at least 20% of the total formulation. Data also indicate that inclusion levels of at least 40% HP‐DDG are likely limiting in lysine.

Yüzer Ağ Kafeslerde Sınıflandırmanın Gökkuşağı Alabalıklarında (Oncorhynchus mykiss) Büyüme Performansına Etkileri

Alabalik yetistiriciliginde buyuk baliklarin kucuklerden ayrilmasinin ve dolayisi ile siniflandirmanin kafes ortaminda ne derece etkili oldugunun belirlenmesi amaciyla yapilan bu calismada iki farkli deneme grubu olusturulmus ve 75 gunluk besleme donemi sonunda besi performanslari degerlendirilmistir. Denemede boylanmis grubu (K) 72,14±3,48 g lik kucuk baliklar olustururken, diger grubu (B+K); %80 kucuk baliklar (71,04±1,10) ve %20 buyuk baliklar (151,8±8,14) olusturmustur. Deneme sonunda (K) grubunun 203,52±16,20 g ortalama canli agirliga ulasirken (B+K) grubunun kucuk bireyleri 185,13±21,77 g, buyuk bireyleri ise 223,25±28,00 g ortalamaya ulasmislardir. Boylanmis gruptaki yem degerlendirme orani (1,61±0,052) diger gruptan (2,17±0,039) daha dusuktur (P<0,05). Elde edilen bu sonuclara gore sadece kucuk bireylerin oldugu ayni boydaki grubun bireylerinin daha iyi buyudugu ve yemden yararlanma oranlarinin daha iyi oldugu ve dolayisi ile %20 oraninda buyuk baliklarin varligi alabaliklarda buyumeyi kotu yonde etkiledigi sonucuna varilmistir. Anahtar Kelimeler: Alabalik, Boylama, Kafes, Yetistiricilik Abstract The Effects of Size Grading on Growth Performance of Rainbow Trout ( Oncorhynchus mykiss ) in Floating Cage Condition In the study, the effects of size grading on growth of rainbow trout in cage condition was examined. Two different test groups were made and after 75 days of daily diets the fattening performance value was analyzed. In the research, the graded group (S) was formed with small fish (72.14±3.48 g) while the other group (L+S) was formed with 80 % of small fish (71.04±1.10 g) and 20% of large fish (151.8±8.14 g). At the end of the study, the average weight of K group was found as (203.52±16.20 g); on the other hand in the group (L+S) the average weight of small fish was determined as (185.13±21.77 g) and the large ones as (223.25±28.00 g). Also feed conversion ratio in group S (1.61±0.052) was found lower than the other group (2.17±0.039). As a result of the study it was found that small fish in the same graded group grew more and feed conversion rate were better. Therefore, the growth performance of trout has been affected adversely by 20 % of large fish in the group (L+S). Key Words: Trout, Size Grading, Cage Aquaculture

Retrospective analysis of antibiotic treatments against piscirickettsiosis in farmed Atlantic salmon Salmo salar in Chile.

Piscirickettsiosis is the most prevalent salt-water infectious disease in farmed salmonids in Chile. Antimicrobials are used to treat this disease; however, there is growing concern about the poor response to therapeutants on some fish farms. The objective of this study was to assess whether factors such as type of antibiotic used, average fish weight, temperature at the beginning of the treatment, and mortality at the time of treatment administration affect the probability of treatment failure against piscirickettsiosis. Pen-level treatment and production information for the first treatment event from 2014 pens on 118 farms was used in a logistic mixed model to assess treatment failure. We defined a failed treatment as when the average mortality 3 wk after the treatment was above 0.1%. Farm and company were included in the model as random effects. We found that the antibiotic product, mortality level before the treatment, and fish weight at the start of the treatment all had a significant effect on treatment outcome. Our results suggest that antibiotic treatment success is higher if the treatment is administered when mortality associated with piscirickettsiosis is relatively low. We discuss the effect of weight on treatment success and its potential relationships with husbandry practices and drug pharmacokinetics.

The use of oral boosters as an alternative to control Piscirickettsia salmonis in farmed salmon in Chile

The use of oral boosters as an alternative to control Piscirickettsia salmonis in farmed salmon in Chile

RNA: DNA Ratio and Growth Performance of Rohu Labeo rohita (Hamilton) Fed Varied Proportion of Protein Diet during Intensive Aquaculture

An experiment was conducted at Corona of Agriculture (COA)”, Gunjanagar-3, Chitwan, Nepal to complete a project granted by University Grant Commission (UGC), Second Higher Education Project (SHEP) in 2013. Four (average 380 m2) ponds (W, X, Y and Z) with four different diets as D1 (20%), D2 (30%), D3 (40%) and D4 (50%) protein contents were used to conduct the experiment properly to determine the varied proportion of dietary protein on the growth performance of major carp rohu Labeo Rohita (H) in relation with RNA: DNA ratio. After 12th weeks of culture, average length, average weight and specific growth rate of fish were found significantly (P&lt;0.05) higher in the carp with D3 and D4 diet fed fish. Similar results were observed in average total protein, albumin and globulin contents. RNA content increased rapidly with age. The average RNA content increased highest in D2 and D3 diet fed fish while, DNA content were highest in D3 diet fed fish. RNA: DNA ratio was recorded highest in D2 and D3 diet fed fish. RNA: DNA ratio, an indicator of protein synthesis and have been used to accurately estimate the growth rate and feeding condition of fish hence, as the dose of protein increased RNA and DNA contents also increased with age of carp cultured during experiment. Thus, it was clear from this study that the incorporation of protein in diet enhances the growth of fish regardless of species weight groups and the doses, as the average weight of fish was significantly lower in control diet fed fish as compared to the treated one.

SUMPIL SILAGE (Faunus ater) AS HIGH PROTEIN FISH FEED ATRACTANT FOR INCREASED PRODUCTIVITY OF FISHERIES

&lt;p&gt;The increase in fish feed demands caused extra fee. Hence it needs to be done diversification of fish feed. Silage are food additives which function as attractants to increase appetite. Sumpil (Faunus ater) are abundance mangrove pests that contain protein. This study aims to utilize sumpil silage as fish food attractant and increase its protein content. Silage was made by mixing sumpil meat and acid of sauerkraut. Silage was incubated for 0, 4, 7, and 11 days and then measured levels of protein with Lowry-Folin method. The highest levels were found in silage of 7 days incubation, which is 153.99 mg/mL. The highest protein level silage mixed with the fish feed. Red tilapia maintained for 3 weeks and was given five treatments and three replications, namely feed A (high protein), feed B (protein medium), feed B+silage 1%, feed B+3% silage, and feed B+silage 5%. The parameters observed were body weight and body length after feed treatment. The results showed that the average weight of fish treatmented by feed B+silage 1% and 3% are greater than the treatment of feed B only but not greater than the treatment of feed A, although the difference was not significant. While the average length of fish relatively the same. On the other hand most rapid response was found in fish treated with feed B+silage 5%. Based on the results, sumpil silage are potential as attractant that could increase fish productivity.&lt;/p&gt;&lt;p&gt;&lt;br /&gt;&lt;strong&gt;Keywords&lt;/strong&gt;: Silage, sumpil, feed, attractants, protein&lt;/p&gt;

A littoral fish index that responds to eutrophication in boreal lakes

Littoral fish assemblages were sampled by electrofishing at 70 nearshore sites in the Kitka lake group (lakes Ala-Kitka, Yli-Kitka and Posionjärvi) in northeastern Finland. Fish assemblages were usually dominated by littoral fish species, especially minnow (Phoxinus phoxinus) and alpine bullhead (Cottus poecilopus). Young individuals (mainly 0+ and 1+) of other fish species, such as burbot (Lota lota) and perch (Perca fluviatilis) were also recorded frequently. A littoral fish index (LiFI) was developed to respond to the degree of eutrophy. Of the candidate metrics, three were chosen for the index: (1) proportion of minnow and alpine bullhead individuals in the electrofishing catch, (2) density of perch, and (3) average weight of all individual fish in the catch. The index value responded to the extent of eutrophy; total phosphorus explained 55.3% of the variation in LiFI index values. A test of the index with data from other Finnish lakes suggested that the index is feasible for use in a broader context. Finally, the index values from the Kitka lakes were classified from bad to high in assessing the ecological status of the littoral sites around the studied lakes. We recommend the use of littoral electrofishing and LiFI index in lakes where detailed, bay-specific information is needed about the ecological status, and in all situations where the littoral zone is in focus.

Using Tournament Angler Data to Rapidly Assess the Invasion Status of Alien Sport Fishes (Micropterus spp.) in Southern Africa.

Fishes are one of the most commonly introduced aquatic taxa worldwide, and invasive fish species pose threats to biodiversity and ecosystem function in recipient waters. Considerable research efforts have focused on predicting the invasibility of different fish taxa; however, accurate records detailing the establishment and spread of invasive fishes are lacking for large numbers of fish around the globe. In response to these data limitations, a low-cost method of cataloging and quantifying the temporal and spatial status of fish invasions was explored. Specifically, angler catch data derived from competitive bass angling tournaments was used to document the distribution of 66 non-native populations of black bass (Micropterus spp.) in southern Africa. Additionally, catch data from standardized tournament events were used to assess the abundance and growth of non-native bass populations in southern Africa relative to their native distribution (southern and eastern United States). Differences in metrics of catch per unit effort (average number of fish retained per angler per day), daily bag weights (the average weight of fish retained per angler), and average fish weight were assessed using catch data from 14,890 angler days of tournament fishing (11,045 days from South Africa and Zimbabwe; 3,845 days from the United States). No significant differences were found between catch rates, average daily bag weight, or the average fish weight between countries, suggesting that bass populations in southern Africa reach comparable sizes and numbers relative to waters in their native distribution. Given the minimal cost associated with data collection (i.e. records are collected by tournament organizers), the standardized nature of the events, and consistent bias (i.e. selection for the biggest fish in a population), the use of angler catch data represents a novel approach to infer the status and distribution of invasive sport fish.

Parrotfish size as a useful indicator of fishing effects in a small Caribbean island

There is an urgent need to develop simple indicators of fishing effects for the implementation of ecosystem-based fisheries management in the Caribbean. In this study, we compare the ability of three simple metrics (average individual fish weight, fish density, and fish biomass) derived from the parrotfish assemblage and from an assemblage of highly valued commercial fish species to track changes in fishing pressure at spatial scales relevant to small Caribbean islands. Between June and August 2011, we conducted five consecutive visual fish surveys at six reefs ≤10 km apart along the west coast of Barbados, representing a spatial gradient in fishing pressure. We used these data to identify the fish metrics most strongly correlated with fishing pressure and describe their functional relationship with fishing pressure. Overall, average individual parrotfish weight and biomass and density of commercial fish species were the metrics most strongly correlated with fishing pressure, although for the latter two, such correlations depended on the range of fish body sizes analyzed. Fishing pressure accounted for most of the variability in all correlated fish metrics (adj R 2 ≥ 0.75). However, functional relationships with fishing pressure differed qualitatively between metrics. In particular, average individual parrotfish weight was the metric most sensitive to incremental changes in fishing pressure. Overall, our study highlights that assemblage-level average individual parrotfish weight deserves a place in the toolbox of Caribbean reef managers as a simple indicator of both fishing effects on parrotfish assemblages and overall fishing pressure on the reef fish community.

Evaluation of Dietary Soy Sensitivity in Snake River Cutthroat Trout

AbstractThe shift in commercial diet formulations for Rainbow Trout Oncorhynchus mykiss toward formulations that include more plant ingredients, specifically an increased inclusion of soy products, may have negative implications for less‐domesticated trout species fed these modern diets. Therefore, the objective of this study was to examine the effects of increasing dietary soybean meal and soy protein concentrate inclusion on growth efficiency and intestinal health of Cutthroat Trout O. clarkii. To achieve this objective, a feeding trial was conducted with juvenile Snake River Cutthroat Trout O. clarkii behnkei fed a practical type formulation that included 0, 5, 10, 15, or 30% dietary soybean meal or soy protein concentrate. Feed and consumption, weight gain, proximate composition, intestinal health, and survival were compared. Juvenile Snake River Cutthroat Trout (initial weight, 28.1 ± 1.0 g/fish [mean ± SD]) were stocked at 20 fish per tank in 200‐L tanks with three replicate tanks per diet. Fish were fed their respective diets for 10 weeks. Final fish weight was affected by dietary soy inclusion level (P = 0.0001) but not type (P = 0.7790), and no interaction was observed (P = 0.6019). Snake River Cutthroat Trout fed the diets with the highest level of soy protein inclusion (30%) were significantly larger than fish fed all other diets and had a final average fish weight of greater than 130 g (P = 0.0001). Feed conversion ratios were higher in fish fed diets with 0% and 5% soy inclusion than in fish fed the 10% or 30% soy inclusion diets (P = 0.0044). No significant effect of soy inclusion level (P = 0.0825) on feed intake was observed. Increased inflammation and decreased vacuolization, however, was observed in histological samples of the intestine of Cutthroat Trout fed the 30% soybean meal and soy protein concentrate diets. Additional research is necessary to determine whether the intestinal pathology observed can predispose Cutthroat Trout to pathogenic disease and/or negatively affect growth with extended feeding.

Seasonal Variability of the Price and Quality of Fresh Red Porgy Fish Sold in the Local Market of Igoumenitsa, NW Greece

Farmed Red porgy (Pagrus pagrus) is one of the “new candidate fish species” for the diversification of Mediterranean aquaculture which is predomintly based on the cultivation of the European sea bass, (Dicenfrarchus labrax), and the gilthead sea bream, (Sparus aurata). The quality of farmed red porgy (Pagrus pagrus) was investigated with samples obtained from the local fish market in the region of Igoumenitsa, NW Greece. Sample of the fish (ungutted and with scales) were purchased from three local fish mongers (the purchased fish were coded as Fish monger 1, 2 and 3) and transported to the laboratory within few minutes, using foamed polystyrene boxes covered with. The average weight of whole fish ranged between 271 and 289g. A sample of the fish flesh taken from the upper epaxial region was transferred aseptically to a stomacher bag containing sterile buffered peptone water solution (0.1%) and homogenized. After serial dilutions in 0.1% peptone water, the homogenates were spread on the surface of agar plates. Total viable counts (TVC) were determined using plate count agar after incubation at 30oC for 3 days. The quality attributes monitored during the present work included bacterial load (total mesophilic) and the pH of the flesh. The pH values varied between 6.54 and 6.69. The results indicate a possible influence of season on the bacterial load of fish sold in the market. Nevertheless, the parameters investigated in the present work indicate that the bacteria load was well below the legal limit and that fish were sold within few days after harvesting. The peak of bacterial load in the summer samples may be a result of a seasonal variability in ambient water temperature as well post harvesting contamination of the farmed fish and temperature fluctuations during handling and transportation.

The utility of simple fish community metrics for evaluating the relative influence of fishing vs. other environmental drivers on Caribbean reef fish communities

AbstractFish community metrics have been extensively investigated as indicators of fishing effects for ecosystem‐based fisheries management (EBFM) in temperate systems. Little similar work has been performed in the coral reefs of the Caribbean, where simple indicators are urgently needed. Here, we use 415 coral reef surveys throughout the Caribbean to assess the potential of four simple and intuitive fish community metrics, namely, fish biomass, fish density, average fish weight and species richness, to separate fishing effects from those of other environmental factors at both local (tens of kilometres) and broad (hundreds to thousands of kilometres) spatial scales. We found that these fish metrics differed considerably in environmental correlates and the spatial scales underlying fish metric–environment associations. Average fish weight and fish biomass were most sensitive to fishing indices at both spatial scales, although average fish weight responded more sensitively and specifically to fishing than fish biomass. Fish density and species richness were most sensitive to temperature over broad scales and to macroalgae and relief height over local ones. All fish metrics were negatively correlated with macroalgae over broad scales, supporting the utility of macroalgae to inform about the integrity of entire reef ecosystems. Most of the fish metric variance associated with fishing pressure operated over broad scales, highlighting the need for a Caribbean‐wide view of fish community status to establish local management objectives and avoid shifting baselines. Our study clarifies the utility of simple fish community metrics as indicators of fishing effects for EBFM in the Caribbean.

English

The aim of this study was to compare serum total cholesterol and cholesterol types of cultured rainbow trout (CRT) (Oncorhynchus mykiss) and cultured brook trout (CBT) (Salvelinus fontinalis) cultivated under the same water conditions. Fishes used in the research were randomly captured from pools and five pieces (five replication) were used for each group. The average weight of fish is 80 g for CRT and is 120 g for CBT. CRT and CBT have been fed with feed with 45 to 50% crude protein twice a day. The levels of serum samples excluding high density lipoproteins (HDL) obtained from the CBT were found to be higher (p&lt;0.05) than that of CRT. Finally, higher serum samples in CBT could have resulted from difference of growth and size, species, age, the cycle of sexual maturity of fish. Key words: Rainbow trout, brook trout, total cholesterol, high density lipoproteins (HDL), low-density lipoproteins (LDL), very-low-density lipoprotein (VLDL). CORRECTION: The introduction section of this article has been rewritten and was republished on 28th August, 2018.

Parrotfish size: a simple yet useful alternative indicator of fishing effects on Caribbean reefs?

There is great need to identify simple yet reliable indicators of fishing effects within the multi-species, multi-gear, data-poor fisheries of the Caribbean. Here, we investigate links between fishing pressure and three simple fish metrics, i.e. average fish weight (an estimate of average individual fish size), fish density and fish biomass, derived from (1) the parrotfish family, a ubiquitous herbivore family across the Caribbean, and (2) three fish groups of “commercial” carnivores including snappers and groupers, which are widely-used as indicators of fishing effects. We hypothesize that, because most Caribbean reefs are being heavily fished, fish metrics derived from the less vulnerable parrotfish group would exhibit stronger relationships with fishing pressure on today’s Caribbean reefs than those derived from the highly vulnerable commercial fish groups. We used data from 348 Atlantic and Gulf Rapid Reef Assessment (AGRRA) reef-surveys across the Caribbean to assess relationships between two independent indices of fishing pressure (one derived from human population density data, the other from open to fishing versus protected status) and the three fish metrics derived from the four aforementioned fish groups. We found that, although two fish metrics, average parrotfish weight and combined biomass of selected commercial species, were consistently negatively linked to the indices of fishing pressure across the Caribbean, the parrotfish metric consistently outranked the latter in the strength of the relationship, thus supporting our hypothesis. Overall, our study highlights that (assemblage-level) average parrotfish size might be a useful alternative indicator of fishing effects over the typical conditions of most Caribbean shallow reefs: moderate-to-heavy levels of fishing and low abundance of highly valued commercial species.

Stocking density of Nile tilapia in cages placed in a hydroelectric reservoir

The Brazilian government has been encouraging fish farming in cages in federal water bodies, including hydroelectric reservoirs. Despite the government support, it is a new activity and the production model still needs some adjustment to reduce the production costs and achieve sustainability. The aims of this study were to determine the appropriate stocking density of Nile tilapia in cages in a hydroelectric reservoir and to evaluate to what extent fish size selection could improve their uniformity. Twelve cages (6m3) were placed at the Fish Farmers' Cooperative of Santa Fé do Sul and Region, Ilha Solteira reservoir, São Paulo, Brazil (20°12′10″S, 50°58′31.15″W). In stage I (initial fish weight, 78g), four stocking densities were tested: D1—800, D2—2000, D3—2500 and D4—3000 fish/cage, with three replicates. At the end of this stage (average fish weight, 255g), the fish were selected into three sizes, except for D1. In stage II, four stocking densities were tested, designed to obtain the following final production: D1—100kg/m3 (800 non-selected fish/cage), D2—80kg/m3 (600 fish/cage), D3—100kg/m3 (800 fish/cage) and D4—120kg/m3 (900 fish/cage). The trial ended when the fish weighed 800g. By reducing the initial stocking density from 2500 to 800 tilapia juveniles per cage, there was no need for selection. The growth performance was higher, the feed conversion rate was better and the time taken to reach harvesting was shorter. Consequently, the production cost reduced and the operating profit increased. Using the lowest initial stocking density, the risk of disease outbreak was also lower, and there was no need to use drugs for disease control since the mortality rate and occurrences of disease and deformity decreased and the dissolved oxygen level inside the cages was higher.

Growth and Acute Temperature Tolerance of June Sucker Juveniles Fed Varying Dietary Protein and Lipid Levels With and Without Supplemental Dicalcium Phosphate

AbstractReports 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 12 weeks of culture, tissue samples were obtained to determine nutrient partitioning. An acute temperature challenge was also conducted to investigate dietary adequacy. Significant effects of diet on growth and temperature tolerance were observed. Fish fed the diet with 45% crude protein gained more weight than did fish fed 40% or 35% crude protein, and fish fed 16% dietary lipid gained more weight than did fish fed 12% and 8% crude lipid. However, the composition of this growth indicated that fish fed the 16% lipid stored larger amounts of lipid in both the visceral cavity and the muscle. A significant negative interactive effect of dietary protein and lipid on temperature tolerance was observed at 45% crude protein and 16% lipid. Results of this study define acceptable ranges of dietary protein and lipid for juvenile June Suckers and provide culturists information to make better choices regarding appropriate diets for this species.