Fish Growth

Decreasing body size has been proposed as a universal response to increasing temperatures. The physiology behind the response is well established for ectotherms inhabiting aquatic environments: as higher temperatures decrease the aerobic capacity, individuals with smaller body sizes have a reduced risk of oxygen deprivation. However, empirical evidence of this response at the scale of communities and ecosystems is lacking for marine fish species. Here, we show that over a 40-year period six of eight commercial fish species in the North Sea examined underwent concomitant reductions in asymptotic body size with the synchronous component of the total variability coinciding with a 1–2 °C increase in water temperature. Smaller body sizes decreased the yield-per-recruit of these stocks by an average of 23%. Although it is not possible to ascribe these phenotypic changes unequivocally to temperature, four aspects support this interpretation: (i) the synchronous trend was detected across species varying in their life history and life style; (ii) the decrease coincided with the period of increasing temperature; (iii) the direction of the phenotypic change is consistent with physiological knowledge; and (iv) no cross-species synchrony was detected in other species-specific factors potentially impacting growth. Our findings support a recent model-derived prediction that fish size will shrink in response to climate-induced changes in temperature and oxygen. The smaller body sizes being projected for the future are already detectable in the North Sea.

A 75-day long experiment was performed to evaluate the effects of probiotic supplementations on rearing water quality, hematology, intestinal morphology, and gut bacterial load of Nile tilapia, Oreochromis niloticus. Fifteen ponds were used for 5 treatments with 3 replications, and 400 fingerlings per pond were fed with pre-starter feed twice a day at 5-8% of body weight. First treatment (T1) was supplemented with the soil probiotic Super PS/ week, T2 was designed to add gut probiotic Zymetin with feed, T3 contained half of the recommended doses of soil, gut, and water probiotics pH FIXER, T4 was planned to supplement with pH FIXER/ week, and no probiotic was used in T5 (control). Growth parameters (net weight gain, weight gain (%) and specific growth rate (%), SGR), survival, feed utilization (feed conversion ratio, FCR and feed conversion efficiency, FCE); water quality (dissolved oxygen, DO, free ammonia, temperature, alkalinity and pH), hematological parameters (RBC, WBC, hemoglobin, glucose, mean corpuscular hemoglobin, MCH), gut bacterial load and intestinal histomorphology (villi length, and enterocyte height) were analyzed fortnightly by sacrificing 3 fish/ treatment. Significant improvements in water qualities, growth performance, feed utilization, hematological parameters, intestinal microbial load and morphology were found with probiotic supplemented treatments than the control group where supplementation of gut probiotic (T2) and combination of soil, gut and water probiotics (T3) significantly augmented growth performance and feed utilization with improved gut microbiota and intestinal morphology. Hence, the findings recommended probiotic supplementation as an eco-friendly health management approach for tilapia aquaculture.

Four isonitrogenous and isocaloric diets, with different α-cellulose inclusion levels, were formulated. Diet with 4 % α-cellulose in it served as control. Fish ranging from 2.6-3.4 gm each were housed in glass aquaria @10 fish per aquarium. Aquaria were provided with 14L/10D fluorescent light. Trial was conducted for 60 days. No mortality was observed in any group. All diets performed equally well. However, the diet with 12 % α-cellulose showed superiority over the rest of the treatments in growth and nutrient digestibility. There was no variation in digestibility of carbohydrates and dry matter contents. Lowest digestibility of fats and protein was observed in 16% α-cellulose containing diet the group which also displayed the lowest growth. The studies have suggested that Labeo fingerlings can tolerate complex carbohydrates up to 16 % if included in the diet but there is a gradual reduction in performance if inclusion level of this carbohydrate exceeds 12 % of the diet.

The population dynamics of Odaxothrissa mento in the lower Cross River, southeast Nigeria, were obtained from a six month length composition data (4.25-14.75 cm TL; mean = 5.91 cm ± 1.02; and 0.71-7.36 g; 1.62 g ± 1.24; n = 1012). The length-weight relationship of the species indicated isometric growth (b = 3.005; r = 0.9623). Three year classes with mean lengths of 7.4 cm, 11.55 cm and 13.3 cm TL, respectively, were identified. The von Bertalanffy exponential growth parameters were estimated as: asymptotic length (L∞) = 13.7 cm TL, growth curvature (K) = 1.48 year-1 and length-at-age zero years, t0 =-0.13; Lo = 2.40 cm TL. The estimated growth performance index, φ′ = 2.444 based on length and φ = 0.6833, using weight. The computed total mortality, Z = 2.54 year-1 , natural mortality, M = 1.58 year-1 and fishing mortality, F was 0.96 year-1. Results indicate the fishery is lightly exploited with current exploitation ratio, Ecur = 0.38 < Eopt = 0.5; rate of exploitation, μ = 0.3481 year-1 < Ecur, 35% of the available stock being fished annually; corroborated by Z/K ratio (< 2) and M/K = 2.08, indicating environmental stability. The length-at-first capture Lc = 5.64 cm TL at age 1.7 yr. The fish was yet to complete 50-55% of growth as at the time of capture at Lc, L25 and L75 compared to L, hence, Lopt = 10.1 cm TL, provides least impact on the stock. This finding serves as baseline for management of O. mento and clupeids/small-sized fish species in the lower Cross River and tropical environments.

Background: The black-chinned tilapia, Sarotherodon melanotheron, is the most abundant fish species in the Nakwa (an open lagoon) and Brenu (a closed lagoon) in the Central Region of Ghana. Aspects of the life history characteristics and the ecology of the fish populations in both lagoons were studied to assess the bio-ecological status of this important resource. Methods: Fish samples were obtained from fishermen that fish on the Nakwa and Brenu lagoons using cast, drag and gill nets. The age of the fish was assessed from otoliths analysis and its growth modelled following the von Bertalanffy growth function. Morphometric characteristics of the fish populations were analysed using power regression and ANOVA for parameters comparisons, and Student's t test to determine whether species grew isometrically. The percentage occurrence method was used to analyse the stomach contents of the fish.

The study was conducted in order to investigate the effect of supplementing various concentrations of canola oil on the growth performance and body chemical composition of Nile tilapia (Oreochromis niloticus, Linnaeus 1758). In the present study, five different experimental diets were used. Control group was fed 100% fish oil (FO) while other groups in triplicate, each of 25 fish, weighing 10 g each on the average were fed varying concentrations of canola oil viz., 25% (CO25), 50% (CO50), 75% (CO75) and 100% (CO100). There was no significant difference among the groups in terms of their growth performance at the end of the experiment (60 days). The better feed utilization was observed for the FO group (P&lt;0.05) indicating higher protein efficiency ratios (PER) and lipid efficiency ratios (LER) than the other groups. The viscerosomatic index (VSI) and the hepatosomatic index (HSI) were not different among the groups (P&gt;0.05). The highest protein content in whole body was determi...

Determining the life history consequences for fishes living in extreme and variable environments will be vital in predicting the likely impacts of ongoing climate change on reef fish demography. Here, we compare size-at-age and maximum body size of two common reef fish species (Lutjanus ehrenbergii and Pomacanthus maculosus) between the environmentally extreme Arabian/Persian Gulf (‘Arabian Gulf’) and adjacent comparably benign Oman Sea. Additionally, we use otolith increment width profiles to investigate the influence of temperature, salinity and productivity on the individual growth rates. Individuals of both species showed smaller size-at-age and lower maximum size in the Arabian Gulf compared to conspecifics in the less extreme and less variable environment of the Oman Sea, suggesting a life-history trade-off between size and metabolic demands. Salinity was the best environmental predictor of interannual growth across species and regions, with low growth corresponding to more sa...

Growth of African catfish (Clarias garipinus) is characterized by large size heterogeneity resulting in poor growth performance and cannibalism. Strategies that limit size heterogeneity in C. gariepinus culture are therefore advocated. This study determined the effects of grading frequency on the growth performance and cannibalism of C. gariepinus in tank culture system. Three treatments designated as G0 (no grading), G2 (grading every 2 weeks) and G4 (grading every four weeks) in a Completely Randomized Design (CRD) was applied in triplicate. The tanks were stocked with 200 fingerlings each. Sampling was conducted weekly to measure length and weight of fish. Mortalities were recorded and dead fish observed under dissecting microscope to ascertain that it is due to cannibalism. Growth performance in terms of final mean weight, weight gain, specific growth rate and food conversion ratio were significantly (P &lt; 0.05) affected by frequency of fish grading. The C. gariepinus graded e...

Walleye (Sander vitreus) populations are declining in Wisconsin and neighboring regions, motivating broader interest in walleye biology amidst ecological change. In fishes, growth integrates variation in ecological drivers and provides a signal of changing ecological conditions. We used a 23-year data set of length-at-age from 353 walleye populations across Wisconsin to test whether walleye growth rates changed over time and what ecological factors best predicted these changes. Using hierarchical models, we tested whether spatiotemporal variation in walleye growth was related to adult walleye density (density-dependent effects), water temperature, and largemouth bass (Micropterus salmoides) catch per unit effort (CPUE; predator or competitor effects). The average length of young walleye increased over time, and as a result, time to reach harvestable size declined significantly. In contrast, average lengths of older walleye have remained relatively constant over time. Juvenile walleye length-at-age was positively correlated with largemouth bass CPUE and surface water temperatures, but negatively correlated with adult walleye density. Our finding of widespread and long-term changes in walleye growth rates provides additional insights into how inland fisheries are responding to environmental change. Résumé : Les populations de dorés jaunes (Sander vitreus) sont en déclin au Wisconsin et dans les régions avoisinantes, ce qui suscite un intérêt accru pour la biologie de ces poissons dans un contexte de changements écologiques. Chez les poissons, la croissance incorpore les variations de facteurs écologiques et constitue un indice de conditions écologiques changeantes. Nous avons utilisé un ensemble de données sur 23 ans de la longueur selon l'âge pour 353 populations de dorés jaunes au Wisconsin afin de vérifier si les taux de croissance de ce poisson ont changé avec le temps et de déterminer les facteurs écologiques qui prédisent le mieux ces changements. À l'aide de modèles hiérarchiques, nous avons vérifié si les variations spatiotemporelles de la croissance des dorés jaunes étaient reliées à la densité de dorés adultes (effets dépendant de la densité), à la température de l'eau et à la capture par unité d'effort (CPUE) d'achigans à grande bouche (Micropterus salmoides) (effets de la prédation et de la concurrence). La longueur moyenne de jeunes dorés jaunes a augmenté dans le temps, de sorte que le temps nécessaire pour atteindre la taille requise pour la capture a diminué de manière significative. En revanche, la longueur moyenne des dorés jaunes plus vieux est demeurée relativement constante dans le temps. La longueur selon l'âge des dorés jaunes juvéniles était positive-ment corrélée à la CPUE d'achigans à grande bouche et à la température de la surface de l'eau, mais négativement corrélée à la densité de dorés jaunes adultes. Les variations répandues et de longue durée des taux de croissance des dorés jaunes ainsi révélées nous en apprennent davantage sur la réaction de ressources halieutiques intérieures aux changements environnementaux. [Traduit par la Rédaction]

The population dynamics of Odaxothrissa mento in the lower Cross River, southeast Nigeria, were obtained from a six month length composition data (4.25-14.75 cm TL; mean = 5.91 cm ± 1.02; and 0.71-7.36 g; 1.62 g ± 1.24; n = 1012). The length-weight relationship of the species indicated isometric growth (b = 3.005; r = 0.9623). Three year classes with mean lengths of 7.4 cm, 11.55 cm and 13.3 cm TL, respectively, were identified. The von Bertalanffy exponential growth parameters were estimated as: asymptotic length (L∞) = 13.7 cm TL, growth curvature (K) = 1.48 year -1 and length-at- age zero years, t0 = - 0.13; Lo = 2.40 cm TL. The estimated growth performance index, φ&#39; = 2.444 based on length and φ = 0.6833, using weight. The computed total mortality, Z = 2.54 year -1 , natural mortality, M = 1.58 year -1 and fishing mortality, F was 0.96 year -1 . Results indicate the fishery is lightly exploited with current exploitation ratio, Ecur = 0.38 &lt; Eopt = 0.5; rate of exploitatio...

The fecundity of the Seabream from the western Mediterranean (Algerian coast) was assessed by the volumetric method using 22 ovaries from females between 169 and 263 mm total length (206.62 ± 19.93). Estimates of total potential annual fecundity varied between 19875 and 49125 oocytes per female (29448.86 ± 8198.12). Relationships between total potential fecundity (F) and total length (Lt), total weight (Wt), gonad weight (Wg) were established using the multiplicative regression model and a significant correlation was found (ANOVA: P‹0.01). RESUMEN Se evaluó la fecundidad de la dorada del Mediterráneo occidental (costa argelina) mediante el método volumétrico utili-zando 22 ovarios de hembras entre 169 y 263 mm de longitud total (206,62 ± 19,93). Las estimaciones del total de fecundidad potencial anual varían entre 19.875 y 49.125 ovocitos por hembra (29448,86 ± 8198,12). Las relaciones entre la fecundidad potencial total (F) y la longitud total (Lt), peso total (WT) y peso de las gónadas (Wg) se establecieron mediante el modelo de regresión multiplicativo obteniendo correlación estadísticamente significativa (ANOVA: P <0,01). BenSahla TaleT lOTFi, MOuFFOk SaliM, BenSahla TaleT ahMed & BOuTiBa ZiTOuni

Fish living in the extreme conditions of the Tatra Mountain lakes were evaluated from a biological point of view as well as an important biomarker of long-range transported pollutants. In Veľke Hincovo pleso and in Morskie Oko, specimens of brown trout (Salmo trutta) of extraordinarily advanced age were found (ages of 18+ and 17+ years, respectively). The capture of a 17+ year-old brown trout in Morskie Oko (2400 g, 540 mm) indicated the presence of the so-called ferox life strategy. The growth of brook trout (Salvelinus fontinalis) was faster than the growth of brown trout in the younger year classes, and while the growth of brook trout stopped after the age of 5+, the growth of brown trout continued. Concentrations of long-range transported pollutants (HCHs, HCB, DDTs, PCBs, PBDEs, and trace metals) in the Tatra Mountain fish were mostly associated with fish age, body weight and length, type of fish tissue, and lake altitude. Persistent organic pollutants (POPs) in fish muscle wer...

Triplicate groups of rainbow trout (Oncorhynchus mykiss) (1.4 0.1 g) were fed experimental diets containing four levels of protein substitution to totally replace fishmeal with poultry by-product meal (0, 33, 67 and 100%). Fishmeal (FM) from tuna fish by-products and poultry by-product meal ‘pet food grade’ (PBM) were used. Diets were formulated to be isonitrogenous (43.5% crude protein) and isolipidic (12.5% crude fat). After 80 days of feeding, no significant differences were found in terms of thermal unit growth coefficient (TGC). However, the EPA levels in muscle tissue among treatments 0PBM, 24PBM and 44PBM were found to be significantly higher than those for the 59PBM diet. Nevertheless, a re-feeding period with the control diet showed that 28 days was long enough to regain the FA profile needed. We concluded that PBM used up to 44% in diets for juvenile rainbow trout can be used without a significantly decrease in EPA and DHA under the present conditions. The use of a whole f...