Average Standard Length Research Articles

Data to the growth of yoy (0+) tenches (Tinca tinca L.) in Tisza Lake

Young of the year (YOY) tenches (Tinca tinca L.) were caught in relatively great number in Tisza-Lake at the Tiszafüred section on last days of October in 2004. The standard length of these fishes varied between 20 and 46 mm. It seemed that the collected sample could provide appropriate data to examine the size-structure of YOY tenches, so we measured their standard body-lengths in mm and -weights in hundred parts of gramm unit. After the statistical analysis were found the follows:1. The curve of length frequency corresponds with normal distribution, i.e. there was not found multimodal curve as could be expected in the case of a periodic spawning species.2. The average standard length of the examined individuals – although the environmental conditions of the population is good – was only 31 mm. It is far below the 37 mm average of the lowest growth of tench population was found in the scientificpapers.3. More than 20% of measured sample belonged to the range of 20-26 mm. The estimated ages of these fish specimens are about 70 days, according the scientificpapers.By right of above mentioned can be concluded that the sample represents only one age-group from a late spawning, and not the whole range of YOY tenches, so these data can give information about the size structure only of this group. The 31 mm average standard length of individuals, origin from spawning in late July or beginning of August is accordance with age and environmental conditions as well.

Feeding of early larval pike Esox lucius L. reared in illuminated cages

The paper presents the results of investigations on the feeding of pike larvae reared in illuminated cages in a mesotrophic lake over a period of 19 days. The same zooplankton species were found both in the lake and illuminated cages. At night, the biomass of all zooplankton groups was higher in illuminated cages than in the lake (with Copepoda prevailing). The first exogenous food of pike larvae (with 13.1 mm average standard length) was cladocerans ( Bosmina, Chydorus) and small copepods ( Cyclops). Pike larvae were feeding throughout the whole period of 24 h, with the greatest intensity at night when illumination was switched on. The most popular zooplankton groups among pike larvae were Copepoda (up to 94.7%) with less numerous Cladocera (up to 28.8%) and other organisms (up to 0.9%). The indices of alimentary tracts filling ( I) of larvae feeding on zooplankton reached up to 1220.5‱. With the age of pike larvae, Ivlev's selectivity indices ( E) with respect to different food components changed—for Chydorus sphaericus and Bosmina sp. they were decreasing, and for Copepoda increasing. Rotifers usually made an insignificant part of the diet. Pike larvae willingly fed on Chironomus plumosus and roach larvae incidentally found in the cages. Cannibalism among pike larvae started when their standard length (SL) was 16.0–22.3 mm (18.7 mm on average). The size of a prey item constituted up to 90.9% of the predator's standard length. After passing over to predatory feeding, gut-filling indices in pike larvae reached up to 2859.6‱. Cannibalism occurred even in case of very low (230 ind. m − 3 ) concentration of pike larvae in cages, which on the 12th day of rearing made 3%; and on the 19th day, 42%. Pike larvae could be reared without additional feeding in illuminated cages up to 2 weeks. Over this period, their mean standard length increased from 13.1 to 20.0 mm. Further rearing of pike larvae does not make any point because their output started to decrease considerably as a result of cannibalism.

Parâmetros eritrocitários do jundiá (Rhamdia quelen) submetido à dieta com diferentes níveis de proteína

O jundiá é espécie de interesse econômico para região sul do Rio Grande do Sul, pois adapta-se a diferentes ambientes e dietas artificiais, apresentando fácil manejo e boa aceitação comercial. O bom estado nutricional é fator determinante no desenvolvimento dos peixes. A formação das células sangüíneas é dependente da manipulação da dieta. O objetivo deste trabalho foi avaliar o efeito da dieta com diferentes níveis de proteína sobre os parâmetros eritrocitários do jundiá. Foram utilizados 90 peixes, com comprimento padrão médio de 20,0±1,2cm e peso médio de 131,4±25,9g. Os animais foram distribuídos em três caixas de 1.000L, contendo três cestos (80L) cada, com três níveis de proteína bruta (30, 40 e 50%). Os animais foram amostrados a cada duas semanas, durante 45 dias. Após serem anestesiados, foi realizada a coleta de sangue através de punção caudal, utilizando-se agulha e seringa que contêm EDTA a 10%. As análises sangüíneas correspondentes à série eritrocitária foram realizadas através de contador automatizado. O nível protéico da dieta influencia os parâmetros eritrocitários, em especial o número total de eritrócitos, a taxa de hemoglobina e o hematócrito, sendo que o nível de 50% de PB foi o que mais estimulou a eritropoiese.

Validation of the stochastic distorted-wave Born approximation model with broad bandwidth total target strength measurements of Antarctic krill

Abstract Total-scattering cross-sections (σt) of Antarctic krill (Euphausia superba) were measured over a broad bandwidth (36–202 kHz) using a new technique based on acoustical reverberation in a cavity. From 18 February to 9 March 2002, mean total target strengths (TTS = 10 log(σt/4π)), were measured from groups of 57–1169 krill (average standard length=31.6 mm; standard deviation=6.6 mm) at the Cape Shirreff field station, Livingston Island, Antarctica, and aboard RV “Yuzhmorgeologiya”. Chirp pulses were transmitted sequentially by an omni-directional emitter into one of three glass carboys containing groups of krill swimming in 9.3, 19.3, or 45.9 liters of seawater (0.6°C≤temperature≤4.0°C). Between each pulse the krill moved within the fixed-boundary tank and the modulated reverberations were sensed bi-statically with three omni-directional receivers. At each center frequency (fc), the coherent energy in 200-pulse ensembles identified sound scattered by the tank. The incoherent energy described total sound scattering from the krill. Thus, the TTS at each fc was extracted from a correlation analysis of energy reverberated in the tank. Measurement bias was determined to be ±0.4 dB from an experiment using metal sphere reference targets, and the precision was estimated as ±0.8 dB from the variability in the krill TTS (fc) measurements. The empirical estimates of mean σt corroborated a krill-scattering model based on the distorted-wave Born approximation (DWBA), enhanced by the authors to account for the stochastic nature of sound scattering (SDWBA), integrated over all scattering angles and averaged over all incident angles (SDWBATTS). The SDWBA, solved for target strength of Antarctic krill, may be the best predictor of backscatter for this important species and may also provide backscattering spectra for improving their acoustic identification. These advances may help to reduce uncertainty in krill-biomass estimation using multi-frequency echosounder data and echo-integration methods.

Food consumption, food passage time, and body measurements of captive Atlantic bottlenose dolphins (<I>Tursiops truncatus</I>)

The food consumption (recorded as kg of individual fish species), body length, and body mass of 19 (four males and 15 females) Atlantic bottlenose dolphins ( Tursiops truncatus )k ept at Harderwijk Marine Mammal Park, the Netherlands, between 1965 and 1995 are reported. This broad-scale, longitudinal study is based on data originally archived for short-term husbandry purposes. The chemical composition and caloric value of the diet were not measured. Because caloric content of fish varies seasonally and annually, and depends on the geographical region where it was caught, the food intake variations seen in this study may reflect the caloric content of the diet. However, because the e ects of age, gender, and reproductive state are consistent in various animals, and all animals entered the study at di erent times, the e ects are believed to be independent of variation in caloric content of the diet. After weaning, the average annual food consumption of males and nonpregnant, non-lactating females increased rapidly until the estimated age of 3‐5 years, thereafter it averaged around 1900 kg (estimated at 133 # 10 5 kJ) per year. After the age of 20 years, food consumption of several dolphins decreased slightly. Two females reproduced and nursed their calves successfully. Twelve months before parturition, consumption by both ceased almost entirely for one week, probably indicating estrus. Food intake did not increase during pregnancy. After they gave birth, the food consumption of the two mothers showed ac omparable pattern; the food intake remained at ac onsistent level during the month of birth, but increased rapidly in the following month. Food consumption dropped during the third month of lactation in one case and during the fourth month in the other case. During the lactation period, the mothers consumed 2600 kg (48%) and 3300 kg (72%) more than during similar periods in non-reproductive years. The two calves began to eat fish, in addition to suckling, at the ages of 6a nd 19 months respectively. Average standard body length at birth was 116 ’ 6c mf or males (n=15) and 114 ’ 10 cm for females (n=6). It increased rapidly until around the age of 5y ears, after which growth rate declined. Body length reached an asymptote (between 260 and 280 cm) between the ages of 15 and 20 years. Average body mass at birth was 18.0 ’ 3.8 kg for males (n=15) and 15.6 ’ 4.9 kg for females (n=5). Weight gain was rapid until around the age of 3y ears, after which it decreased. The relationship between body mass and standard body length was: Body mass (kg)=12.904e 0.017(body length (cm) 100) . There was an egative relationship between body mass and average daily food consumption expressed as ap ercentage of body mass. The average initial passage time of food through the digestive tract of five animals (with an average body mass of 185 kg) was 235 min.

Determinação do sistema endócrino difuso nos intestinos de três Teleostei (Pisces) de água doce com hábitos alimentares diferentes

O objetivo do presente trabalho foi o de verificar a presença de células endócrinas nos intestinos médio e posterior, ou reto, e nos cecos pilóricos de três espécies tropicais de peixes Teleostei de água doce com hábitos alimentares diferentes: piracanjuba, (Brycon orbignyanus) e piau (Leporinus friderici), onívoro; e surubim (Pseudoplatystoma coruscans), carnívoro. Para tanto, foram utilizados sete exemplares da piracanjuba, com médias de peso e comprimento-padrão de 410,16 ± 66,33 g e 27,42 ± 1,17 cm, respectivamente, 13 exemplares de piau com médias de 77,71 ± 24,31 g e 14,84 ± 1,56 cm de peso e comprimento-padrão, respectivamente; e cinco exemplares do surubim com médias de peso e comprimento-padrão de 309,91 ± 94,23 g e 32,70 ± 1,79 cm, respectivamente. Pode-se constatar a presença de células endócrinas do "tipo aberto" nos segmentos referentes aos intestinos médio e posterior das espécies onívoras e do "tipo fechado" no intestino médio e no reto da espécie carnívora. As células argirófilas foram observadas entre as células absortivas do epitélio intestinal. Os resultados permitem concluir que a presença de células endócrinas nas espécies estudadas pode indicar que estas atuam no mecanismo de controle da absorção dos nutrientes do alimento.

Interannual and regional variations in body length, weight and energy content of age‐0 Pacific herring from Prince William Sound, Alaska

Age‐0 Pacific herring were surveyed in October of 4 years in a large northern Gulf of Alaska estuary, to determine the range of variations in length, weight and whole body energy content (WBEC). These parameters reflect their preparedness for surviving their first winter's fast. During the surveys there were distinct regional and interannual variations in all three parameters for individual groups of herring in Prince William Sound. Likewise, with each collection there was typically a large range of size and WBEC values. The average standard length was (±S.D.) 80±13 mm (range=40–118), the mean whole body wet weight was 5·7±3·0 g (range=0·7–29·2) and the average WBEC of all age‐0 herring captured, regardless of year or site (n=1471), was 5·4± 1·0 kJ g−1 wet weight (range=2·4–9·4). The large range of WBEC and size indicates that age‐0 herring at different capture sites were not all equally prepared for surviving their first winter.

Momento de formación y periodicidad de los microincrementos de crecimiento en otolitos de larvas de pejerrey (Austromenidia regia) mantenidas en laboratorio

In order to know the periodicity and the moment of first growth microincrement formation in the sagitta otolith of pejerrey larvae (Austromenidia regia) were maintained in the laboratory for 26 days. The photoperiod and temperature were maintained constant. Larvae were fed ad libitum with plankton, artificial food for fishes and Artemia sp. nauplii. Five larvae were sacrificed at regular intervals; it standard length was measured then the sagittae and lapillus otoliths were extracted. The otoliths were reading by two readers counting twice each one, with more than three microincrements of diference in the reading were discarded. At larvae hatch present an average standard length of 7,3 mm, reaching an average standard length of 12,3 mm at the final of the experimental period. The regression analysis between the number of microincrements and the age in days, delivery the following parameters: a = 5,86 y b = 0,98, resulting the slope significantly equal to one. The regression intercept indicates that larvae hatching with approximately 6 microincrements, which it was corroborated with the analysis of otoliths of larvae newly hatching.

The effects of predation on the survival and size-distribution of estuarine fishes: an experimental approach

The effect of southern flounder,Paralichthys lethostigma, predation on the survival and size-distribution of spot,Leiostomus xanthurus, was investigated using feeding experiments in outdoor tanks and estuarine ponds. In the outdoor tank experiments, southern flounder, 143 mm average standard length (SL), fed for 48 h on spot (25–30 mm SL), over a range of densities (4–20 m−2). In these trials, flounder showed a Type II functional response to spot density. In the estuarine pond experiment, flounder density (2 or 4 flounders 70 m−2) contributed significantly to spot mortality relative to predator-free controls. The effect of flounder density on spot mortality was non-linear; in the 4-flounder treatment the daily instantaneous mortality due to flounder (0.0177) was 3.5 times that in the 2-flounder treatment (0.0051). The total spot mortality rate in the 4-flounder treatment (0.028) was similar to that observed from published field observations. Flounder also altered the size distribution of spot relative to predator-free controls. Predation by flounder resulted in fewer intermediate-sized spot at the end of the experiment when compared to predator-free controls. Flounder also significantly reduced survival and mean length of two killifishes,Cyprinodon variegatus andFundulus heteroclitus, that invaded the pond. Flounder predation was a significant size-structuring force on the prey fish assemblage in the pond. Results from both the outdoor tank experiment and the pond experiment indicate that flounder may represent a significant source of mortality for juvenile estuarine fishes.

Observations on a leatherback turtle Dermochelys coriacea nesting population near Piguwa, Papua New Guinea

Some aspects of the reproductive biology and conservation of leatherback turtles Dermochelys coriacea on an important nesting beach near Piguwa, Papua New Guinea, were studied in December 1989. Leatherbacks had an average overcurvature standard carapace length of 161·35 cm and laid a mean of 88·2 eggs. The eggs had a mean diameter and weight of, respectively, 52·20 mm and 81·05 g. Statistically significant positive relationships were found between the carapace lengths of nesters and the sizes and weights of their clutches. Nesters spent an average of 74 min at the nest site. The nests were about equally distributed on the front and rear halves of the beach and only a few nests were constructed below the beach scarp. Leatherback eggs, an important source of protein and currency for local inhabitants, are heavily harvested in December and January. A high-density nesting section of the beach was recommended for Wildlife Management Area (WMA) status. This means that the traditional beach owners, with the support of the federal government, would regulate the sustainable harvesting of leatherback eggs on the WMA. Ecotourism, centered on the nesting leatherbacks, is a distinct possibility.

Culture of grunion Leuresthes tenuis (Ayres) larvae to metamorphosis, in the laboratory

A total of 800 larvae of the grunion Leuresthes tenuis, obtained by means of fertilization and artificial incubation, were cultured under laboratory conditions. The method used to incubate the eggs is described. The larvae were cultured to metamorphosis, 40 days after hatching, in rectangular tanks with 20 litres of seawater and stocking density of 10 larvae.l–1. The larvae were fed with recently hatched Artemia nauplii, at a concentration of 500 naupliil–1 the first 20 days and 1,000 nauplii.l–1 the next 20 days. The nanoflagellate Tetraselmis suecica was added to the culture medium. Growth, survival and condition factor (body height/standard length) were recorded throughout the culture period. Forty days after hatching, the average standard length of the larvae was 15.1 mm, larval growth was linear and represented by the equation L = 7.40 + 0.19 t (n = 14, r2 = 0.99, p < 0.0001). Final average survival was 76.6%. The larvae of the grunion L. tenuis are easy to culture in the laboratory and require relatively less food than larvae with similar characteristics. Therefore, they are a good alternative for experimental cultures.

Biological evaluation of frozen zooplankton as food for milkfish (Cbanoschanos) fry

Summary Milkfish fry with an average standard length and weight of 13.88 mm and 3.95 mg, respectively, were reared for 30 days using live and frozen Moina macrocopa and Brachionusplicatilis at feeding densities of 10–20 individuals per ml. Growth, survival and yield were used as indicators of the overall performances of the various treatment groups. Fry fed live M. macrocopa showed gains (both length and weight), growth and survival rates and yields significantly higher than fry fed with other treatment groups (P < 0.05). However, significant reductions in growth and survival rates resulted when fry were fed frozen M. macrocopa. On the other hand, there were no significant differences in growth and survival rates (P < 0.05) in fry fed live or frozen B. plicatilis. The results of the current study showed that although milkfish fry could be grown successfully using B. plicatilis, feeding with live Moina significantly improved growth, survival rate and yield (P lt; 0.05). Frozen Moina was found to be unsuitable as a feed for rearing milkfish fry because it reduced growth rates and increased mortality. Comparisons between live and frozen rotifers have proven the suitability of frozen rotifers as feed for rearing milkfish fry. By freezing surplus rotifers this would permit short term storage in anticipation of high hatchery demand and overcome any unpredictable failures with live cultures.

A Thyroxine Surge during Development of Black Sea Bream Larvae and its Ecological Implication in Inshore Migration.

The tissue concentration of L-thyroxine (T4) was measured by radioimmunoassay for whole bodies of laboratory-reared black sea bream larvae from 12 to 38 days after hatching. T4 level was less than 2ng/g body wet weight in early postlarvae. It increased markedly from 1.7ng/g on day 19 to 7.0ng/g on day 24, and then gradually decreased to 2.4ng/g by day 33, followed by the second elevation to 5.0ng/g on day 38. The first surge, occurring on day 24, corresponded to the notochord postflexion phase (Fukuhara's I stage) at which average standard length was 6.1mm. Previous field research on the early life history of this species suggests that this phase corresponds to the critical phase when the larvae migrate from coastal waters to near-shore nursery areas. Thus, it seems possible that thyroxine is involved in habitat transfer during the early ontogeny of the black sea bream.

Difference of Average Standard Length in Heterozygous or Homozygous Individuals at The Isozymic Loci in Cultured Stocks of Rainbow Trout in Japan.

Relationship between fitness advantage of isozymic genotype and a state of genetic constitution in a stock was examined in cultured stocks of rainbow trout in Japan. A number of stocks exhibited a larger average standard length in heterozygouse individuals under a state of “heterozygote excess” stocks at the Idh-3, Pgm-2 and Sod, significantly. However, an additive effect of advantage of heterozygotes at the three loci could not be observed. It sug-gests a fitness advantage of individuals heterozygous at each locus in cultured stocks of rainbow trout. On the other hand, a few stocks exhibited a larger standard length in homo-zygous individuals under a state of “homozygote excess” at the three loci, suggesting a fitness advantage of homozygous individuals. The mechanism of such phenomena could be explained by the relationship between the state of genetic constitution and quantity of dereterious genes in such a stack. An appearance of a larger average standard length in heterozygotes than in homozygotes could be explained by the resulting of a low fitness in homozygote individuals including many deleterious genes in the stocks. An appearance of larger average standard length in homozygotes than in heterozygotes could be explained by the elimination of deleterious genes during the process of inbreeding

Growth and productivity of orange roughy(Hoplostethus atlanticus)on the north Chatham Rise

Abstract A new interpretation of orange roughy (Hoplostethus atlanticus) otoliths indicates that growth rates in this species are exceptionally slow. The otolith interpretations were supported by modal analysis of length‐frequency distributions of small juveniles. Parameters of the von Bertalanffy growth function were estimated to be L8 = 42.50 cm standard length (SL), K = 0.059 year−1 and t0 = ‐0.346 year. This gives an average SL after 1, 2, and 3 years of growth of only 3.1, 5.5, and 7.6 cm, respectively. The estimated average age of maturity is 20 years. It is further suggested that maximum age may exceed 50 years, the instantaneous rate of natural mortality is probably below 0.10, and spawning success may be highly variable. This combination of factors makes orange roughy susceptible to overfishing. The optimal instantaneous rate of fishing mortality is estimated to be less than 0.10.

Comparison of Pond-Culture Characteristics between Atlantic and Gulf Coast Red Drum Fingerlings

Abstract Fry of red drum (Sciaenops ocellatus) from Gulf of Mexico and Atlantic coast brood stocks were cultured in fertilized saltwater ponds during spring and fall 1987 to compare production and growth characteristics. Ponds were fertilized with a combination of cottonseed meal, phosphoric acid, and urea. Fry were stocked at an average rate of 674,000 fry/hectare 2–4 weeks after pond filling. Spring production ranged from 2.11 to 3.19 kg/hectare daily, and survival ranged from 65.9 to 86.4%. Fall production values were 1.00–2.67 kg!hectare daily; survival ranged from 24.5 to 50.4%. Survival and production were similar between the two geographic populations of red drum. For both seasons combined, average standard length of Atlantic red drum fingerlings ranged from 15.6 to 26.2 mm, and weight ranged from 0.10 to 0.34 g; Gulf of Mexico fingerlings ranged from 19.5 to 23.7 mm and 0.16 to 0.26 g. No clear pattern of superior growth, production, or survival was found for either Gulf of Mexico or Atlantic red drum fingerlings in saltwater ponds.

Food of the emperor penguin Aptenodytes forsteri on the Antarctic fast ice edge in late winter and early spring

The food of emperor penguins Aptenodytes forsteri at the edge of the sea ice off the Vestfold Hills was studied by faecal analysis. Fish, crustacean, cephalopod and gastropod remains were found in 151 droppings collected between August and October 1984. The main fish identified from otoliths was Pleurogramma antarcticum with an average standard length of 129.5 mm. Amphipods increased in frequency from August to October with gammarids predominating.

Development and early life history of the greenlings Hexagrammos otakii (Pices: Hexagrammidae) reared in the laboratory.

The larval development and growth of Hexagrammos otakii are described based on a series of 716 reared specimens, ranging between 7 and 50mm standard length (SL). Details on development of larvae and juvenile stages are illustrated, with special reference to segmentation and branching of the fins. Transformation from the larval to the juvenile stage occurred between 14.7 to 18.7mm SL, (18.0 to 23.3mm in total length). Segmentation of all the fin rays finished completely by the time the larvae attained about 20mm in standard length. The larvae grew slowly up to the transitional phase, and rapidly afterwards attaining an average SL of 46.1mm at 105 days after harching.

Kepone®: Chronic Effects on Embryo, Fry, Juvenile, and Adult Sheepshead Minnows (Cyprinodon variegatus)

We investigated the toxicity of Kepone to, and uptake by embryo, fry, juvenile, and adult sheepshead minnows (Cyprinodon variegatus) using intermittent-flow toxicity tests. Concentration of Kepone and percentage of adult fish surviving in a 28-day exposure were: Control, 95%; 0.05 μg/liter, 95%; 0.16 μg/liter, 100%; 0.80 μ/liter, 78%; 1.9 μg/liter, 20%; and 7.8 μg/liter and 24 μg/liter, 0%. Concentration factors (concentrations in fish divided by concentrations measured in water) for adult fish averaged 5,200 (range 3,100 to 7,000). Symptoms of poisoning included scoliosis, darkening of the posterior one-third of the body, hemorrhaging near the brain and on the body, edema, fin-rot, uncoordinated swimming, and cessation of feeding. Adults surviving the first exposure were spawned, and the embryonic development, hatching, and survival and growth of fry and juveniles were monitored in a 36-day exposure to Kepone concentrations of 0.08, 0.18, 0.72, 2.0, 6.6, and 33 μg/liter. A significant number of embryos from adult fish exposed to 1.9 μg of Kepone/liter of water developed abnormally and died even when incubated in Kepone-free water. Kepone in water was not as lethal to progeny as to adults: 36-day LC50 for juveniles was 6.7μg/liter; 28-day LC50 for adults, 1.3 μg/liter. However, the average standard length of juvenile fish was significantly reduced by exposure to 0.08 μg of Kepone/liter of water; some fish developed scoliosis. Concentration factors in juvenile sheepshead minnows averaged 7,200 and increased from 3,600 to 20,000 as exposure concentrations decreased.

Une etude sur clarias senegalensis val. dans la region du lac kossou (cote d'ivoire)

A study on Clarias senegalensis Val. in the region of Lake Kossou (Ivory Coast). Clarias senegalensis is the dominant silurid of the man-made lake Kossou and some smaller impoundments in the same region. Comparison of data spread over a five year period starting from 1970, some months before the dam was completed, reveals that the density of C. senegalensis dropped to the original level that existed in the river after reaching a peak in the years following the damming. This phenomenon which coincides with the impoverishment of the lake waters, is explained by the fact that C. senegalensis has its optimal habitat in poorly oxygenated waters, rich in organic matter. It is able to colonize this kind of productive waters thanks to the suprabranchial organ. In these optimal conditions it mainly feeds on aquatic insects and plankton. The fecundity of C. senegalensis may reach 20o ooo ripening eggs per female. Reproduction occurs during the rainy season in flooded savannas. Growth rates are very high and the age determinations show that, in the region of Kossou, C. senegalensis reaches an average standard length of 620 mm (2.7 kg) within three years. Our results are compared to literature data on other related species of the genus Clarias and the position of C. senegalensis within this generic complex is discussed.