Intensive culture of lake whitefish (Coregonus clupeaformis Mitchill) using Artemia and artificial feed

Whitefish larvae were reared using combinations of live Artemia nauplii and trout starter. In all cases survival was greater than 93% at 9 weeks of age. Growth did not differ significantly (P>0.1) between high and low feeding rates of live nauplii; however, an opercular cover malformation was detected at the lower rate. A conversion program was developed for the practical use of Artemia nauplii. Whitefish were successfully converted to trout starter at 7 weeks of age and 140 mg. Trout starter alone was inadequate for early rearing. Decapsulated, lyophylized cysts of Artemia were almost a replacement for live Artemia nauplii except for a low incidence of opercular cover malformation. Advanced rearing to yearling size was easily performed with trout feed. Additional mortalities were less than 3% to 14 months of age at stocking.     

Reproductive roles predict sexual dimorphism in internal and external morphology of lake whitefish,Coregonus clupeaformis

Abstract – The different reproductive roles of the sexes can predict the direction and magnitude of sexual dimorphism of external and internal morphology. Males should have enlarged structures that enhance the acquisition of mating opportunities, whereas females are predicted to have enlarged organs that are associated with the production of eggs. We tested these predictions in male and female lake whitefish, a species in which both sexes have similar overall body size and shape. After controlling for body size, male lake whitefish had significantly longer jaws and pectoral and pelvic fins, larger hearts, and more muscle than females. Sexual dimorphism in relative muscle mass may be one of the most fundamental morphological differences between males and females. Females had relatively heavier livers than males. Because the liver is important for the breakdown of fats and vitellogenesis, selection should favour an enlarged liver in females for the processing of energy and the production of large numbers of eggs.     

Neoechinorhynchus rutili (Müller, 1780) (Acanthocephala) in the whitefish Coregonm nasus (Pallas) sensu Svärdson from the Bay of Bothnia

Abstract. The occurrence of Neoechinorhynchus rutili (Müller, 1780) in the white-fish Coregonus nasus (Pallas) sensu Svardson from the Bay of Bothnia was investigated in 772 fish obtained as monthly or bimonthly samples during the period July 1975-January 1977.
In both years most parasites were found only in November and December. All of the 402 parasites found were immature and very small. Most of them were in the first third of the intestine, and only a few were attached to the mucosa. No encysted parasites were found in other any tissues. It is thus suggested that the whitefish of the Bay of Bothnia is only an accidental host for N. rutili .
A clear correlation was found between the importance of ostracods in the diet and the occurrence of N. rutili . The first intermediate host in the Bay of Bothnia was shown to be an ostracod, Candona neglecta (Sars.).     

大眼狮鲈、湖鲱、湖白鲑引进技术

长期以来,黑龙江省水产养殖业一直以养殖四大家鱼为主,养殖品种结构单一,无法满足人们的需求。为了调整我省渔业养殖品种结构,引进国外优良品种,学习国外现代化的养殖技术和先进的管理经验,哈尔滨市农业科学院水产研究分院(原哈尔滨市水产研究所)与加拿大萨斯卡切温省环境厅合作,在聘请加拿大渔业专家进行技术指导的同时,先后派出科研人员20余人到加拿大鲑鳟鱼养殖场、科贝尔堡孵化站、多伦多大学等地进行学习,重点针对养殖品种、养殖技术与加拿大渔业专家进行了充分的技术交流,引进了适合我省养殖条件的大眼狮鲈、湖鲱、湖白鲑等3条优质冷…     

池养条件下湖白鲑幼鱼的生长和食性的观察

池塘饲养的湖白鲑，其幼鱼的体长与日龄呈直线相关，体重与日龄，体长与体重均呈幂函数相关。此外，还对湖白鲑幼鱼做了食性的分析：湖白鲑幼鱼阶段是以动物性铒料为主的杂食性。     

Planktivory and diet-overlap of densely rakered whitefish (Coregonus lavaretus (L.)) in a subarctic lake

Abstract –  Three sympatric whitefish ( Coregonus lavaretus (L.)) forms, one being pelagic and two benthic, segregate available habitat and food resources in subarctic Lake Muddusjärvi, northern Finland. Zooplankton availability in the lake, food composition, diet-overlap and growth of densely rakered (DR) whitefish were examined during June to September to explore the reasons for the small individual size of the pelagic form. DR whitefish used zooplankton as main food item and prey selection followed zooplankton species density proportions in the lake. Zooplankton density and water temperature was highest in July–August. The average lengths of Bosmina spp., Daphnia spp., Calanoida and Cyclopoida in DR whitefish stomach were higher than in zooplankton sample during June–September, except Calanoida in June. Diet-overlap between DR whitefish age groups was high at all months indicating intercohort resource competition. DR whitefish reached sexual maturity at 3 years of age and at the length of 12 cm, after which somatic growth almost ceased. Reason for the small average size and slow growth of DR whitefish were connected to high diet-overlap between age groups and early sexual maturation.     

湖白鲑幼鱼对常用水产药物敏感性的试验

在水温为 1 6～ 1 9℃的条件下 ,进行了敌百虫 ( 90 %晶体 )、NaCl、ClO2 、甲醛、CuSO4和FeSO4合剂 ( 5∶2 )对湖白鲑幼鱼 ( 2 2～ 74mm)的耐受性试验 ,试验结果表明 :湖白鲑幼鱼对 5种水产常用药物敏感性的大小顺序为 :敌百虫 ( 90 %晶体 ) >CuSO4和FeSO4( 5∶2 )合剂 >甲醛 >ClO2 >NaCl。NaCl、ClO2 、甲醛、CuSO4和FeSO4合剂 ( 5∶2 )可以作为湖白鲑的鱼病防治药物使用 ,敌百虫 ( 90 %晶体 )不能作为湖白鲑的鱼病防治药物使用。     

Food availability and growth of the brook trout, Salvelinus fontinalis (Mitchill), in a French Alpine lake

Plan Vianney lake, situated in the Oisans massif (French Alps) at an altitude of 2250 m, has a fish fauna composed of brook trout, Salvelinus fontinalis (Mitchell), and Artic charr, Salvelinus alpinus (L.). The present study examines the feeding behaviour of S. fontinalis in 1993–94 but also gives some data on S. alpinus . The brook trout represented 80% of the fish fauna of the lake. Dietary analysis showed that this species is an opportunistic feeder and revealed similarities in the trophic niches of S. fontinalis and S. alpinus and a low level of potentially available food resources. The annual growth of S. fontinalis was short and the growth rate was slow compared with other populations. Under these extreme conditions, female fish required several summers to replenish their reserves of energy and were only in condition to spawn once every 2 or 3 years. Although the fecundity of the population was low, it was sufficient to maintain the species in the lake which is not exploited.     

A metacercarial disease in the dogfish species Umbra limi (Teleostei) and a trematode infestation in a Physa sp. (Mollusca)

A metacercarial infestation is reported in Canadian Umbra limi and a mass infestation by trematodes in Physa sp. from the same locality. Trials made by using parasitised snails showed that both parasites are not of the same species.     

Polymorphic mountain whitefish (Prosopium williamsoni) in a coastal riverscape: size class assemblages,distribution, and habitat associations

We compared the assemblage structure, spatial distributions, and habitat associations of mountain whitefish (Prosopium williamsoni) morphotypes and size classes. We hypothesised that morphotypes would have different spatial distributions and would be associated with different habitat features based on feeding behaviour and diet. Spatially continuous sampling was conducted over a broad extent (29 km) in the Calawah River, WA (USA). Whitefish were enumerated via snorkelling in three size classes: small (10–29 cm), medium (30–49 cm), and large (≥50 cm). We identified morphotypes based on head and snout morphology: a pinocchio form that had an elongated snout and a normal form with a blunted snout. Large size classes of both morphotypes were distributed downstream of small and medium size classes, and normal whitefish were distributed downstream of pinocchio whitefish. Ordination of whitefish assemblages with nonmetric multidimensional scaling revealed that normal whitefish size classes were associated with higher gradient and depth, whereas pinocchio whitefish size classes were positively associated with pool area, distance upstream, and depth. Reach‐scale generalised additive models indicated that normal whitefish relative density was associated with larger substrate size in downstream reaches (R² = 0.64), and pinocchio whitefish were associated with greater stream depth in the reaches farther upstream (R² = 0.87). These results suggest broad‐scale spatial segregation (1–10 km), particularly between larger and more phenotypically extreme individuals. These results provide the first perspective on spatial distributions and habitat relationships of polymorphic mountain whitefish.     

Consequence of habitat segregation to growth rate of two sparsely rakered whitefish (Coregonus lavaretus (L.)) forms in a subarctic lake

Abstract  – The aim of this study was to explain the growth differences of the two sympatric sparsely rakered whitefish ( Coregonus lavaretus (L.)) forms in the subarctic Lake Muddusjärvi by comparing their habitat and food selection to available benthic food resources. The average number of gillrakers was 22.9 for large sparsely rakered whitefish (LSR) and 16.8 for small sparsely rakered whitefish (SSR). LSR dwelled primarily in the littoral zone at depths < 10 m, whereas SSR used mostly profundal habitats in depths > 10 m. LSR and SSR consumed mainly benthic macroinvertebrates, their abundance, biomass and diversity was highest in the littoral, decreasing towards the profundal. As the individual size of fish increased, LSR was able to shift to larger food items, which were available in the littoral. Possibility of SSR to ontogenetic food shift was scarce in the profundal, where availability of larger benthic macroinvertebrates was low. Because of abundant food resources in the littoral, growth rate of LSR was faster than that of SSR.     

Rearing of coregonid fishes (Coregonidae) in illuminated lake cages: IV. Gonad development in whitefish (Coregonus lavaretus L.) under conditions of cage culture

The paper presents the results of observations on gonad development in whitefish (Coregonus lavaretus L.) in the fourth year of culture in illuminated like cages. Whitefish ovaries attained stage III of maturity. Stage IV of maturity was attained by only a few individual females. Disturbances in the development of the ovary were observed, consisting of asynchronous growth of the oocytes, their partial resorption, and delayed trophoplasmatic growth. Development of male gonads was also disturbed. Different males matured at different times, and their testes were in different stages of maturity. Fishes did not attain sexual maturity by the end of the fourth year of cage culture, so that no spawning could have taken place.     

Behavioural characteristics of loggerhead turtles (Caretta caretta) in a submerged bag net of a setnet observed in a bycatch simulation and the development of a turtle releasing device

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Spatiotemporal patterns of mountain whitefish (Prosopium williamsoni) in response to a restoration of longitudinal connectivity

To examine the role of longitudinal connectivity on the spatial and temporal dynamics of mountain whitefish (Prosopium williamsoni), we quantified movement and population dynamics following installation of the Landsburg Dam fishway, Cedar River, WA, USA. Mountain whitefish is widely distributed, poorly studied and not the focus of restoration. Before the fishway, mountain whitefish were not observed above the dam. Here, we focus on snorkel counts collected at reach and mesohabitat (e.g. pools) scales over 11 summers on the 20‐km above‐dam segment following restoration. A camera within the ladder provided number, size and movement timing, thereby informing on behaviour and recolonisation. Segment‐scale abundance increased following fish passage reaching an asymptote in 7 years, and mountain whitefish were detected throughout the main stem in 10 years. Annual movement through the ladder increased over time and was positively correlated with instream abundance and discharge, but negatively correlated with water temperature. About 60% of fish movements occurred in spring and early summer, potentially for foraging opportunities. Reach‐scale abundance peaked between 7 and 10 km from the dam; deep, cool (~10.6 to 11.6°C) conditions characterised these reaches. At the mesohabitat scale, mountain whitefish detection increased with depth and velocity after accounting for distance from the dam. Our results show how restoring longitudinal connectivity allowed this nontarget species to colonise newly available habitat. Their response supports the critical roles of longitudinal connectivity and environmental conditions, that manifest at different spatial scales, in dictating how freshwater fish respond to habitat disturbance.     

The dynamics of gonad growth and ascorbate status in yellow perch, Perca flavescens (Mitchill)

Yellow perch, Perca flavescens (Mitchill), caught in the wild (Grand St Marys Lake, Ohio) and cultured in the laboratory were used to examine the relationship between gonad development and the concentration of ascorbic acid in ovaries, testes, liver and kidney. In wild fish the ovary had concentrations of ascorbate twice as high (75-102 μg g^-1) as the testis (28-48 μg g^-1), and when the differences in gonadosomatic indices between sexes were accounted for, females deposited 10-fold more of this essential nutrient in gonads than did males. Yellow perch cultured intensively throughout the gonadal recrudescence had shown a decrease of ascorbate concentration in the kidney, liver and ovary during winter, most likely due to the low dietary level of the vitamin. Diet enrichment with ascorbic acid resulted in a dramatic increase of ascorbate in ovary and other tissues. Incorporation of ascorbic acid may take place during the late vitellogenesis, and this vitamin deserves to be studied as a quality indicator in fish eggs.     

Comparison of exploited and unexploited yellow perch Perca flavescens (Mitchill) populations in Nebraska Sandhill lakes

Exploitation can have a pronounced effect on fish populations. Yellow perch, Perca flavescens (Mitchill), populations in Nebraska Sandhill lakes were sampled in 1998 and 1999. Three of the 29 lakes containing yellow perch have been closed to fishing for at least 10 years. Unexploited yellow perch populations had fast growth rates, but age structure was similar to exploited populations. For unexploited lakes combined, mortality and condition were not different from exploited lakes. However, one unexploited lake, Marsh Lake, had the fastest growth, highest proportion of older fish and highest condition of all populations sampled. This lake had low interspecific competition and high invertebrate abundance, which likely resulted in fast growth and high condition. However, size structure and growth were also related to lake productivity. Although exploitation may affect yellow perch populations, other factors (food availability, predators and lake productivity) also play an important role in structuring these populations. Regardless, these results indicate the potential of yellow perch in Nebraska Sandhill lakes given no exploitation.