Studies on the influence of nutria on carp growth

Summary Data from 9 experiments with nutria growing on fish ponds were studied. In the cases when no carry-over effect occured from prolonged nutria breeding, the following results were obtained:The statistical analysis showed the high significance of these results and their close fit to the curve of the function of the increase in carp yield in dependence on nutria density.Breeding of nutria on a fish pond during a year leaves a carry-over effect which increases the yield of carp in the next year by 0.7–0.8 kg per nutria. In two cases of prolonged breeding of nutria, the yield increase per one nutria grew from 1.6 to 2.3 and from 1.7 to 2.5 kg.     

Seasonal trends in physicochemical factors and plankton of a freshwater fishpond and their role in fish culture

Summary A two year study on seasonal variations of the physicochemical factors and plankton of a freshwater fish pond was made. The importance of these factors in fish culture has been discussed. pH ranging between 7.3 and 8.4 falls within the range considered suitable for fish growth. The amount of dissolved gases at any given time is found to be associated with biological activities taking place in the medium. The relatively high total alkalinity values observed may also help in higher yield of fish. Low phosphate content is attributed to utilisation by phytoplankton. Most plankters exhibit a single annual peak, though individual species have different seasons of maxima. Volume and dry weight values also showed a single peak suggesting a period of maximum production. However, year to year variations observed in total quantity of plankton is likely to affect fish growth and production.This work formed part of the thesis submitted for the award of degree of Doctor of Philosophy to Calcutta University, India in 1964.     

Growth parameters estimates for a small fish of the Pantanal, Brazil: Moenkhausia dichroura (Characiformes; Characidae).

Growth parameters were estimated for Moenkhausia dichroura (Kner, 1858) (Characiformes, Characidae), a small-sized and very abundant fish of the Pantanal lentic habitats commonly known as "pequira ". A method based on the length frequencies distribution and the ELEFAN I routine from the FISAT program were used. The fish were collected in the Baia da On?a, an oxbowlake of the sub-region Pantanal of Aquidauana, Mato Grosso do Sul, Brazil, from June to December 1988. The standard length of the captured fishes ranged from 29 to 76 mm with an average of 53 mm. The estimated growth parameters were L(infinity) = 81 mm (standard length), k = 0.85 year(-1), C = 0.89, WP = 0.6 (Rn = 0.285). The WP indicated that growth reduction occurred in July, when the lowest temperature of the year was registered. The growth curve showed that captured individuals belonged to three cohorts. The obtained results seem robust and quite compatible with the biology of the fish and its adjustment to the environment. M. dichroura, in spite of not being a direct fishing interest, is an important species in terms of its ecological aspects, due to its abundance and high growth rate, and as a great food source for aquatic organisms and specially for larger fish of economic value. Considering the information gap about small fish, the parameters estimated for pequira constitute a comparison base for other growth studies of small-sized fish species of tropical environments.     

Landscape variables affecting fishery yield in lake systems of the Central Amazon region, Brazil

According to fisheries data, lakes are important systems for fish production in the Amazon basin. However, there is no information about the relationship between landscape variables and fishing yield that allows foresight into potential resource exploitation in this environment. The present study aims to evaluate this relationship with the hypothesis: lakes of different shapes give the same fishery yield in the Amazon, after considering the effects of lake size, distance to the river, fishing effort, fuel and ice used. Fishery data from 1994 to 1996 were analyzed with regard to 3228 trips on 50 lakes of the main white water tributaries of the Amazon basin. Analysis of covariance was applied to test this hypothesis. With variables such as fishing grounds access, fishing effort and lake shape the model explained a significant 72% of variabilities in the fisheries yield. Fishing yields among lake systems were different, thus the null hypothesis was rejected (P < 0.05). Results indicate that dendritic lakes far distant from the main river have greater productivity than floodplain lakes because there are more habitats of fish refuge for reproduction and feed available to the fish; there are also more limitations to access by predators.     

Possible Reason for the Expansion of Carassius auratus (Linnaeus, 1758) (Teleostei,Cyprinidae) in the Danube River Basin

The author found quite a close negative relationship between commercial catches of predatory fishes and of German carp (Carassius auratus) in the lower Danube. He supposes that the main reason for the population explosion and subsequent expansion of German carp in the Danube River basin seems to be a shift in the balance of the fish community due to a reduction in the density of predatory species.     

Reproductive and growth strategies of the red roach, Rutilus arcasii (Steindachner, 1866), in two contrasting tributaries of the River Duero, Spain

The life-histories of red roach were assessed in the R. Moros and the R. Ucero, two contrasting tributaries of the R. Duero. Growth occurred from April to October and Ucero red roach were larger than those in the Moros from their second year onwards. Condition increased with gonad development and abruptly decreased after spawning in both populations. The condition of Ucero fish recovered during the summer, but that of the Moros fish remained low. The same year classes (1980 and 1982) dominated both populations. River Moros red roach spawned in a 4-week period between the end of April and early June, while the spawning season of Ucero red roach lasted until August. The length to fecundity relationship was similar for both populations, and fecundity and ovum size increased with fish length. The life-history traits of these red roach populations are discussed in relation to current life-history theories.     

Relationship between body size and habitat complexity preference in age-0 and -1 year winter flounder Pseudopleuronectes americanus

The interaction between body size, habitat complexity and interstice width on habitat preference of age-0 and -1 year Pseudopleuronectes americanus was examined using continuous remote video observation. The habitat choices of juvenile P. americanus were recorded over a 6 h period in tanks with four treatments: bare sand, sand with low complexity cobble, sand with intermediate complexity cobble and sand with high complexity cobble. Both age-0 and -1 year fish preferred cobble to bare sand. Within cobble treatments, age-0 year fish preferred intermediate complexity cobble, with a 1.59 ratio of interstitial space to body width. The largest age-1 year fish (123-130 mm standard length, L(S) ) preferred low complexity cobble. While a significant preference was not detected, medium age-1 year fish (83-88 mm L(S) ) tended to select low complexity cobble, whereas small age-1 year fish (73-82 mm L(S) ) tended to select low and intermediate cobble, with an interstitial space to body width ratio of 1.05. For medium and large age-1 year fish, there was an increased selection of low complexity cobble, corresponding to larger interstitial space to body size ratios. This study indicates that juvenile P. americanus prefer complex habitat to unstructured habitat and that this preference is mediated by a relationship between fish body size and the size of structure interstices. These results contribute to the growing body of knowledge of complex habitat selection and drivers of habitat choice in flatfishes.     

Size-selective mortality of Sea of Okhotsk pink salmon in the ocean in the winter and spring

The mortality of Sea of Okhotsk pink salmon in the winter and spring varies significantly from year to year, which complicates forecasts of its arrival in the following year based on data on the downstream migration of fry and surveys in the fall. The size-selective mortality of pink salmon was studied and the possibility of using the size and weight parameters of juveniles for predicting their return was evaluated through measurements of scale increments in juvenile pink salmon that were caught in the southern Sea of Okhotsk in the fall of 2007 and 2008 and in fish of these year classes that came back to spawn. In the 2007 year class, which had a low overwinter survival level in the ocean, the average scale increments for the first year of life were considerably smaller than those in adult fish that returned to the spawning grounds. In the pink salmon of 2008, which had a very high level of overwinter survival, the values of scale increments in juveniles and adults were similar. This confirms the hypothesis of a critical size and a critical period, according to which slowly growing juveniles that do not accumulate enough energy reserves for summer are eliminated in the winter to a greater extent as compared to fast-growing fish. Correlation analysis revealed a significant negative relationship between the size and weight of juvenile pink salmon and their mortality in the ocean. After conducting further and more extensive studies this will allow using the size parameters of juvenile pink salmon as one of predictors of its return for the year following the fall surveys. These results emphasize how important it is to take the size and growth rate of juvenile salmon into account when forecasting their return.     

The structure,diversity and somatic production of the fish community in an estuarine coastal lagoon,Ria de Aveiro (Portugal)

The present study aims to determine biological fish production of a lagoon and relate this to the commercial fisheries yield. The fish community of an estuarine lagoon in the west coast of Portugal was sampled between November 1998 and November 2000 to estimate the production ecology of the community, including somatic production, population size, species richness, species diversity, and biomass. Using the Allen curve method of determination, the total annual fish production of all fish species in the lagoon was calculated at 90.3 tonnes or 2.1 g m⁻² year⁻¹ in the first year and 106.7 tonnes or 2.5 g m⁻² year⁻¹ in the second year. The marine seasonal migrant species, sardine, Sardina pilchardus, which colonises the lagoon during the juvenile period of its life stages, produced more than 35 tonnes in each year and accounted for >39 and >33%, in the first and second year respectively, of the total fish production in this lagoon. Sardine was numerically more abundant (18,217 specimens) but due to their small size contributed only 13% to the total biomass. Sardine was thus the most important fish species in terms of the consumption and production processes of the whole fish community in this system. Commercial fisheries’ records indicate that approximately 300 tonnes per annum of fish are taken from the lagoon, which corresponds to three times more than the estimated production in the lagoon. Thus, if it exists, the sustainability of the fishery appears to depend on the immigration of fish from the adjacent coastal area and it is questioned whether the fishery is sustainable in the long-term. The findings indicate that careful and effective management of the lagoon is required to ensure a long-term healthy aquatic environment and sustainable catches in the future.     

Assessing the Risk of Hydroxybenzene Contamination in Fish Raised on a Chinese Aquaculture Farm

We estimated the risk posed by hydroxybenzene in farm-raised Crucian carps (Carassius carassius) from a pond on a fish farm in Beijing, China, by analyzing a time-series of observed hydroxybenzene concentrations in fish within a culturing season in year 2006. We used the basic linear regression to model the data and forecast the probability of hydroxybenzene concentration in pond fish exceeding selected health effect criteria (the risk) using Monte Carlo simulation. The risk is highly correlated with the time a fish stays in the pond. The results indicate that the risk–days in pond relationship resembles a sigmoid function with an inflection point around 150 days. The resulting model can be used to demonstrate the benefit of improving water quality in terms of increased fish production.     

浙江披山海域主要鱼类时空生态位

依据2015年11月(秋)、2016年2月(冬)、5月(春)、8月(夏)4个航次的渔业资源底拖网调查数据,运用相对重要性指数(IRI)、Shannon指数和Pianka指数对浙江披山海域主要鱼类的时空生态位宽度和重叠进行分析,并结合冗余分析和种间竞争系数研究了主要鱼类间的竞争共存关系及生态位分化。结果表明: 研究期间共采集鉴定鱼类61种,隶属13目29科48属,其中主要鱼类(IRI>100)有19种。绿鳍鱼与丽叶鲹的时间生态位重叠值最高,二者对时间资源利用的同步性最强;孔虾虎鱼与断线舌鳎的空间生态位重叠值和时空生态位重叠值均最高,二者在空间资源序列上的同域性最强,同时,物种对时空二维资源的利用趋于一致。披山海域时空二维生态位显著重叠(Q_ik>0.6)的种对仅占总种对数的5.8%,表明物种时空分布的差异较大,时空生态位重叠受季节变化的影响比较明显,种间竞争系数计测结果与生态位重叠基本一致。冗余分析揭示了主要鱼类与温度、盐度、溶解氧等环境因子之间的关系,进一步解释了物种间的生态位分化。     

Using otolith weight to age fish

The problem of determining and verifying ages of fish, from populations having a considerable variation in size at age, has been investigated using the relationship between otolith size and fish size, which has been shown by several authors to be influenced by growth rate. In such a population of Sardinella aurita Val. an index of age can be obtained for individual fish by calculating the equivalent otolith weight at a particular fish length, using the otolith weight–fish length relationship determined for each age group. This statistic not only permits a much greater proportion of fish to be assigned ages than is possible with otolith reading alone, but also enables the age groups to be verified as year classes. However, it is concluded that, although appropriate models based on otolith-fish size relationships can predict age for groups of fish in which growth rates are known or can be assumed to be consistent, such techniques have a limited application in ageing fish from wild populations with highly variable growth rates.     

The age, growth and reproduction of the stone loach Noemacheilus barbatulus (L.) in a Dorset chalk stream

SUMMARY.

• 1 In this highly productive chalk stream the stone loach, sampled by electrofishing over a 30 month period, had a high growth rate reaching a mean length of 65 mm in 1 year and 93 mm in 2 years. The fish were short-lived in contrast to most slow-growing populations in the U.K. and Finland with 11 group fish comprising 8.8% and III group fish only 1.1% of the total number.
• 2 The loach were fractional spawners: a 75 mm female produced an estimated 10,620 eggs between late April and early August totalling 46% of the loach's initial weight.
• 3 In March and April some small 0 group females contained only poorly developed eggs and up to 10% of 0 group fish may have failed to spawn.
• 4 Amongst loach >52 mm in length in March and April there was an exponential relationship between absolute fecundity and fish length but no relationship between relative fecundity and length. There was. however, a relationship between fish length and both gonadosomatic index and maximum egg size, which may indicate that large fish began to spawn first.

     

Yield per recruit of the pacu Piaractus mesopotamicus (Holmberg, 1887) in the pantanal of Mato Grosso do Sul, Brazil.

Among the several fish species comercially exploited at the Pantanal of Mato Grosso do Sul, the "pacu" (Piaractus mesopotamicus) stands as one of the most important. Information regarding its exploitation level is necessary for the proper management of its stocks. Between 1996 and 1997 data on total length of the pacu were collected on a monthly basis from specimens caught by professional and sport fishers in the municipality of Corumbá. These data were used to estimate growth parameters and to assess the exploitation level for this species, applying the Beverton and Holt yield per recruit model. Length frequency analysis, carried out with the software FISAT (ELEFAN), was used to estimate growth parameters: 1996: L(infinity) = 87.20 cm; K = 0.34 year(-1); phi(')=3.41; C = 0.74; WP = 0.81; Longevity = 8.40 years; and 1997: L(infinity) = 86.50 cm; K = 0.34 year(-1); phi(')=3.40; C = 0.60; WP = 0.80; Longevity = 8.40 years. The value for t(0) is -0.363 years for mean values of L(infinity) and k. The weight-length relationship, calculated from data derived from experimental fisheries carried out in 1999 and 2000, is described by the equation: W = 0.048LF(2.835). Estimated mortalities and survival rates were: 1996: Z = 1.51 year(-1); M = 0.62 year(-1); F = 0.89 year(-1); S = 21.9%; and 1997: Z = 1.65 year(-1); M = 0.63 year(-1); F = 1.02 year(-1); S = 19.1%. The yield per recruit analysis showed the following values: F(Present) = 0.96 year(-1); F(max) = 0.67 year(-1) ; F(0.1) = 0.51 year(-1) (for L(c) = 26.7 cm). These results suggest that the pacu is overexploited in the area, so that restrictive measures are in need to manage the pacu fisheries.     

The influence of flood regime on fish catch and fish communities of the Cross River floodplain ecosystem,Nigeria

Synopsis The morphology, climate and flood regime of the Cross River floodplain are summarized and related to the catch, species distribution and abundance of the economically important fishes of the floodplain ecosystem. Two flood indices, FI-1 and FI-2, are used to assess, statistically. the relationship between fish catch and flood regime. There are good positive correlations between the catch (C_T) of year T and the flood index 1 of 1 year T-1 and between (C_T) and the sum of the flood indices 1 and 2 of year T-1 (r = 0.6516 and 0.6894, respectively, both at P = 0.05). Cross River is a relatively highly productive system (in terms of fish catch) and this productivity is attributable mainly to the yearly flooding of the plain when fish find allochthonous food materials in the expanded habitat. Changes in hydrometeorological conditions, such as the drought that affected the northern part of the Cross River basin in 1983–1984. if they persist can effectively reduce fish catch from the system.     

Seasonal studies of the biology of Achtheres percarum in perch, Perca fluviatilis, from four Finnish lakes over a 3-year period

Achtheres percarum infection on the gills of perch Perca fluviatilis was studied from four lakes in central Finland in monthly or bimonthly samples of fish during a 3-year period. The highest prevalence and intensity of infection (30%, 0.7 copepods/fish) were found in the oligotrophic, unpolluted Lake Peurunka and the lowest (6%, 0.1 copepods/fish) in the eutrophic and polluted Lake Vatia. According to hierarchical loglinear models the prevalence of A. percarum infection was related to the lake, but not to the year. However, when logit models were constructed such that two 'seasons' ('cold' and 'warm' periods) were included, it was apparent that the year also influenced the prevalence of A. percarum , but only during the 'warm' period of the year. Achtheres percarum had an age dependent relationship only in Lake Peurunka, where the infection increased with increasing age of the fish. Some developmental stages of A. percarum parasitizing the gills of perch are described. Data on the seasonal occurrence of A. percarum developmental stages are given and it is suggested that at least two generations are produced annually.     

Aspects of the biology of Galaxias maculatus

The biology of three landlocked and a riverine population of Galaxias maculatus were examined in western Victoria, Australia. All systems supported reproducing populations of these fish, including Lake Corangamite which had salinities that on occasion reached 82. Spawning sites in Lake Corangamite were located in adjacent tributaries and not in the main lake as was the case for other populations. The smallest fish were found in the fresh water Lake Purrumbete and the largest in the hypersaline Lake Corangamite. The size at which 50% of the population attained sexual maturity varied across sites, with fish maturing at a smaller size in Lake Purrumbete, followed by the Merri River, Lake Bullen Merri and Lake Corangamite. Condition was higher in the freshwater Lake Purrumbete and there was no relationship between condition and temperature, conductivity, turbidity and pH; but there was a positive relationship between condition and dissolved oxygen. Length frequency analysis suggested that the majority of fishes live for a year.     

细鳞斜颌鲴的养殖及其生物学研究

细鳞斜颌鲴是在我国分布较广而又为群众所喜爱的一种野生经济鱼类。这种鱼在某些天然水体中可成为优势种群,产量较大,最高可以占总渔获量的50%以上。但有许多水体中却没有这种鱼或数量不大。通过试验和研究,我们已能对这种鱼进行大规模的人工繁殖和苗种培育,近年来,已将数万尾大规格鱼种投放到一原来只投放“家鱼”(泛指鲩、青、鲢、鳙,以下均同)的水库中,并将检验其增产效果。实践证明斜颌鲴在池塘中与现有“家鱼”混养时,非但不影响“家鱼”的生长,并可使池塘总产量增加10%以上;原因是这种鱼主要以其他养殖鱼类尚未利用或未能充分利用的腐屑、腐泥和着生藻类为食物。该鱼头两年生长较快,两周年可达一市斤左右,并第一次达到性成熟,这种规格的鱼上市就是经济价值高的优良食用鱼。因其在池塘中易于捕捞,故也是丰产塘中轮捕轮放的好对象。按普通“家鱼”种的培育方法当年鱼可养成4寸左右,第二年底都能在半斤以上,大的可达8两半。由于该鱼头小肉多而味美,故即使2—3两重的鱼在市场上也受到顾客的欢迎。本文还介绍了养殖这种鱼的方法及其有关的生物学资料,并讨论了在天然水体中促使这种鱼增产的可能途径。       

Seasonal relationships of ovary weight, liver weight and fat stores with body weight in the goldfish, Carassius auratus (L.)

The relationships of ovary weight, liver weight and visceral lipid stores to body weight in the goldfish were examined at different times of the year. Both arithmetic and logarithmic relationships were examined. Ovary weight significantly increased relative to increasing body weight in goldfish and the exact nature of this relationship changed from month to month. However, larger fish were found to have proportionately larger ovaries than small fish at specific times of the year. Regression lines for liver weight versus body weight were also determined. Monthly differences were found in the liver weight-body weight relationship. Visceral lipid stores expressed per gram of protein were found to be independent of body weight. Lipid stores expressed in this manner peaked in February while ovary weight peaked in April. The consequences of compensating for body size when expressing organ (liver, ovary) sizes, such as hepatosomatic index and gonosomatic index, are discussed.     

The dependence of fish community structure and dynamics on floodplain and riparian ecotone zone in Parana River,Brazil

Flood intensity was a main factor determining access to the riparian/floodplain ecotonal resources of the upper Parana River, Brazil, and in consequence determining yield of the dominant trophic groups, which are fish feeding on flooded grasslands and on riparian fruits and leaves. Prey and predator density both declined in years of low floods, and predators did not recover until the next year of high flood, more slowly than in the case prey fish, most probably due to differences in life cycle length. The life cycle of one of the most important species, Curimba (Prochilodus lineatus — Characidae) depends on access to the floodplain lagoons and return to the reservoir after maturation for intensive growth. The riparian/floodplain habitat complexity and connectivity has great significance for fish community dynamics and fisheries yield, and may serve a reason to create a national park in the last floodplain section of the upper Parana River.