PERMANENT GENETIC RESOURCES: Isolation and characterization of microsatellite loci from the Arctic cisco (Coregonus autumnalis)

Eight polymorphic microsatellite loci were isolated and characterized for the Arctic cisco, Coregonus autumnalis. Loci were evaluated in 21 samples from the Colville River subsistence fishery. The number of alleles per locus ranged from two to 18. Observed heterozygosity of loci varied from 0.10 to 1.00, and expected heterozygosity ranged from 0.09 to 0.92. All eight microsatellite markers were in Hardy-Weinberg equilibrium. The loci presented here will be useful in describing population structure and exploring populations of origin for Arctic cisco.     

Long-term increases in young-of-the-year growth of Arctic cisco Coregonus autumnalis and environmental influences

Arctic cisco Coregonus autumnalis young-of-year (YOY) growth was used as a proxy to examine the long-term response of a high-latitude fish population to changing climate from 1978 to 2004. YOY growth increased over time (r2 = 0·29) and was correlated with monthly averages of the Arctic oscillation index, air temperature, east wind speed, sea-ice concentration and river discharge with and without time lags. Overall, the most prevalent correlates to YOY growth were sea-ice concentration lagged 1 year (significant correlations in 7 months; r2 = 0·14-0·31) and Mackenzie River discharge lagged 2 years (significant correlations in 8 months; r2 = 0·13-0·50). The results suggest that decreased sea-ice concentrations and increased river discharge fuel primary production and that life cycles of prey species linking increased primary production to fish growth are responsible for the time lag. Oceanographic studies also suggest that sea ice concentration and fluvial inputs from the Mackenzie River are key factors influencing productivity in the Beaufort Sea. Future research should assess the possible mechanism relating sea ice concentration and river discharge to productivity at upper trophic levels.     

Influence of cisco (Coregonus artedi,Lesueur) on muskellunge (Esox masquinongy,Mitchill) mean length,population size structure,and maximum size in northern Wisconsin lakes

Population size structure and maximum size of managed sportfish populations are dictated by abiotic, biotic, ecosystem, and anthropogenic influences. In their native ranges of northern Wisconsin, muskellunge (Esox masquinongy) and cisco (Coregonus artedi) are co-adapted cool- and cold-water species where cisco presence may influence population size structure and maximum size of muskellunge. We tested whether muskellunge size structure indices (length-frequency distributions, proportional size distribution), mean length, and mean maximum length of muskellunge differed when cisco were present or absent in Ceded Territory of Wisconsin (CTWI) lakes during 2015–2018. Cisco presence had a positive influence on size structure and mean length of individual muskellunge within populations. In contrast, cisco presence had no influence on the mean maximum length of muskellunge observed in CTWI populations suggesting that other factors may be better predictors of this metric than cisco presence. In cisco lakes, mean muskellunge length was negatively correlated with mean cisco length suggesting that gape limitation may be a factor influencing population size structure and individual growth rates. Therefore, cisco populations with primarily large individuals may be unavailable to muskellunge as forage. Our results suggest that cisco are an important forage species for some aspects of muskellunge population ecology; however, other factors may also contribute to muskellunge population size structure and maximum size outcomes. As such, conservation of remaining cisco populations in Wisconsin is critical because they influence muskellunge population ecology in lakes where the species coexist. Future research is needed to better understand the interactions of cisco, abiotic and biotic factors, and anthropogenic influences on muskellunge growth dynamics.     

Food and food selection of cisco (Coregonus albula L.) in a dysoligotrophic lake

With minor exceptions, cisco (C. albula) in Lake Suomunjärvi fed on cladocerans and copepods. The food habits were different among two size classes of fish. The composition of cisco diet changed at different depths and times of the day, but the distribution of zooplankton was usually very similar in each period irrespective of the depth or diel period. Daphnia, Bosmina, Cyclops scutifer and Heterocope appendiculata were the main diet of cisco. Calculations of fish electivity indices showed that cisco selected usually large species of cladocerans and copepods and a small cladoceran, Bosmina coregoni. Body-size selection was clear for Daphnia and Bosmina.     

Different growth trends of whitefish (Coregonus lavaretus) forms in the northern Baltic Sea

The sea growth of two whitefish forms, anadromous (Coregonus lavaretus lavaretus) and sea‐spawning (Coregonus lavaretus widegreni), was analysed using samples collected from the commercial sea catch in the Gulf of Bothnia (GoB) in the northern Baltic Sea during 1998–2014. In the GoB area, these two forms are possible to identify because the gill‐raker number and size at maturity vary between forms. The growth rate of the forms is linked to their feeding area. Sea‐spawning whitefish, which has a feeding migration near its home site, was shorter in the northern GoB (66°N–64°N) at the ages of 3–11 than those in the southern GoB (64°N–60°30′N). In the data, most whitefish were caught with gill nets in the GoB. The mesh sizes of gill nets capturing the anadromous form were mostly 35–45 mm, while those capturing the sea‐spawning form were <35 mm in the northern GoB. It is likely that the different growth trends for small and large whitefish were connected with differences in their recruitment for fishing. The length of anadromous females at the age of four sea years increased significantly, but the length of six‐year‐old anadromous female whitefish decreased over the catch years from 1998–2014. In contrast, the length of slow‐growing sea‐spawning whitefish of six years or older increased significantly in relation to the catch year in the gill‐net catch. The increase in the growth of young age groups in both forms was probably associated with the increasing temperature and the low fishing pressure on small fish. The decreasing age at capture for both forms and the depression of the mean size of old anadromous whitefish are signs of high fishing pressure with a high gill‐net effort that selectively removes the largest and oldest individuals of both forms.     

温度和盐度对皱肋文蛤幼贝存活与生长的影响

在室内控制条件下,研究了不同海水温度和盐度对皱肋文蛤(Meretrix lyrata)幼贝存活与生长的影响。结果表明:皱肋文蛤幼贝适宜生存温度为12.2-35.6℃,最适生存温度为24-30℃;适宜生长温度为23.5-33.0℃,最适生长温度为27-30℃,属典型的南方滩涂贝类。皱肋文蛤幼贝适宜生存盐度为4.3-40.5,最适生存盐度为11-31;适宜生长盐度为17.1-33.4,最适生长盐度为19-23,属广盐性滩涂贝类。该贝低温和高温敏感起始点分别为21℃和33℃;低盐和高盐敏感起始点分别为9和33。皱肋文蛤幼贝对极端温、盐度具有一定的耐受力:在37℃下仍可保持6d,100%不死亡,在39、41℃下分别在3d和5d内全部死亡;在4、6、8、10、12℃下则可分别100%存活3、4、6、9、11d;在盐度为0、5、7、9时保持100%存活的时间分别为5、8、10、10d;在盐度为33、35、37、39时保持100%存活的时间分别为7、5、3、3d,盐度41时当天即出现死亡。     

Temperature requirements for growth and survival of larval vendace, Coregonus albula (L.)

Water temperatures from 15.0 to 20.0° C are recommended as the most suitable for sustained production of larval vendace, as indicated by the developmental rates, the instantaneous rates of growth, mortality, and the net biomass gain of larvae reared at eight constant temperatures from 4.8 to 22.1° C. The recommended temperatures are optimal when the available food and photoperiod are not the limiting factors. Temperatures higher than 22.0° C will cause increased mortality, whereas temperatures lower than 15.0° C, although advisable when food is limited, will retard larval growth and development.     

Effects of temperature and salinity on the growth of Alexandrium (Dinophyceae) isolates from the Salish Sea

Toxin‐producing blooms of dinoflagellates in the genus Alexandrium have plagued the inhabitants of the Salish Sea for centuries. Yet the environmental conditions that promote accelerated growth of this organism, a producer of paralytic shellfish toxins, is lacking. This study quantitatively determined the growth response of two Alexandrium isolates to a range of temperatures and salinities, factors that will strongly respond to future climate change scenarios. An empirical equation, derived from observed growth rates describing the temperature and salinity dependence of growth, was used to hindcast bloom risk. Hindcasting was achieved by comparing predicted growth rates, calculated from in situ temperature and salinity data from Quartermaster Harbor, with corresponding Alexandrium cell counts and shellfish toxin data. The greatest bloom risk, defined at μ >0.25 d^?1, generally occurred from April through November annually; however, growth rates rarely fell below 0.10 d^?1. Except for a few occasions, Alexandrium cells were only observed during the periods of highest bloom risk and paralytic shellfish toxins above the regulatory limit always fell within the periods of predicted bloom occurrence. While acknowledging that Alexandrium growth rates are affected by other abiotic and biotic factors, such as grazing pressure and nutrient availability, the use of this empirical growth function to predict higher risk time frames for blooms and toxic shellfish within the Salish Sea provides the groundwork for a more comprehensive biological model of Alexandrium bloom dynamics in the region and will enhance our ability to forecast blooms in the Salish Sea under future climate change scenarios.     

The survival and growth of Gammarus tigrinus Sexton (Crustacea: Amphipoda) in relation to salinity and temperature

Field collections from an inland saline lake indicated that a rapid increase in numbers of a population of Gammarus tigrinus was positively correlated with high summer temperatures and salinities. The laboratory experiments on growth are an attempt to determine whether high summer temperatures or optimum salinity were primarily responsible for the rapid increase in numbers. Furthermore, G. tigrinus was not found in either of two adjacent lakes; one non-saline, the other at a higher salinity. The laboratory experiments on survival are an attempt to determine whether the restricted distribution of G. tigrinus was related to salinity. The implications of the field and laboratory studies are discussed and compared with other data from Europe and North America.     

Mortality and growth responses of Daphnia carinata to increases in temperature and salinity

1.  Daphnia carinata King, a freshwater cladoceran, occurs in Lake Waihola, a tidal lake with seasonal fluctuations in temperature (4–21 °C), and salinity (30–2000 mg L^–1 Cl). We hypothesise that these fluctuations influence the seasonal changes in D. carinata abundance.
2. To test this hypothesis, adults and juveniles were exposed to combinations of temperature and salinity. We measured mortality of adults and juveniles, growth of juveniles over 20 days, and their age at first reproduction.
3. The salinity tolerance of adult D. carinata was temperature-dependent. Juveniles were more sensitive to salinity, but more tolerant of temperature increases.
4. Growth rates were higher at elevated temperatures, but reduced by elevated salinities. The onset of reproduction was earlier at elevated temperatures.
5. We conclude that seasonal changes in temperature and salinity contribute to seasonal population changes of D. carinata .     

Effects of temperature, salinity, and fish size on growth and consumption of juvenile bluefish

Consumption and growth rates of juvenile bluefish Pomatomus saltatrix increased with increasing temperature and decreased with increasing fish size in short-term (7 days) experiments. Salinity had no effect on growth or consumption rate in a short-term experiment. In a long-term (90 days) mesocosm experiment, consumption and growth rates declined with increasing body size. Predictive equations developed from short-term experiments did not adequately predict observed consumption rates in the mesocosm experiment. However, growth in the mesocosm experiment was similar to field growth. Also, mesocosm consumption rates and consumption rates calculated using field growth and mesocosm growth efficiencies were similar to published independent field estimates of consumption rate. Our results indicate that experiments to determine the effects of temperature and the allometry of body size on growth and consumption rates should be conducted over long time periods simulating field conditions. Juvenile bluefish have rapid growth and their individual cumulative consumption is large. This result suggests that bluefish may have a large effect on their prey populations. This effect has yet to be quantified.     

Genetics, recruitment, and migration patterns of Arctic cisco (Coregonus autumnalis) in the Colville River, Alaska, and Mackenzie River, Canada

Arctic cisco Coregonus autumnalis have a complex anadromous life history, many aspects of which remain poorly understood. Some life history traits of Arctic cisco from the Colville River, Alaska, and Mackenzie River basin, Canada, were investigated using molecular genetics, harvest data, and otolith microchemistry. The Mackenzie hypothesis, which suggests that Arctic cisco found in Alaskan waters originate from the Mackenzie River system, was tested using 11 microsatellite loci and a single mitochondrial DNA gene. No genetic differentiation was found among sample collections from the Colville River and the Mackenzie River system using molecular markers (P > 0.19 in all comparisons). Model-based clustering methods also supported genetic admixture between sample collections from the Colville River and Mackenzie River basin. A reanalysis of recruitment patterns to Alaska, which included data from recent warm periods and suspected changes in atmospheric circulation patterns, still finds that recruitment is correlated to wind conditions. Otolith microchemistry (Sr/Ca ratios) confirmed repeated, annual movements of Arctic cisco between low-salinity habitats in winter and marine waters in summer.     

Effects of temperature,salinity and their interaction on growth of the benthic dinoflagellate Ostreopsis cf. ovata (Dinophyceae) from Japanese coastal waters

Benthic dinoflagellates of the genus Ostreopsis produce palytoxin (PTX)‐like compounds. The worldwide distributed Ostreopsis ovata/O. cf. ovata is potentially responsible for outbreaks of human health problems around the coasts of tropical, subtropical, and temperate regions. The present study examined growth responses of an O. cf. ovata strain s0662 collected from coastal waters of Japan with 35 different combinations of temperature (15–35°C) and salinity (20–40) and discusses the bloom dynamics of the organism in Japanese coastal environments. The O. cf. ovata strain s0662 tolerated a wide range of temperature (17.5–35°C) and salinity (25–40). Results of a two‐way ANOVA showed significant effects of temperature‐salinity interaction on growth rates and biomass yields of the O. cf. ovata strain (F(24,70) > 127, P < 0.001). The strain showed a maximal growth rate (1.03 divisions day^?1) and biomass yield (240 relative fluorescence) at temperature 25°C and salinity 30. The high growth rates of over 1.0 division day^?1 were obtained in conditions of temperature 25–30°C and salinity 30–35, which indicates that strain s0662 prefers high temperature and salinity conditions. The growth rates of O. cf. ovata under the optimal conditions were higher than those of other benthic toxic‐dinoflagellates, Coolia monotis, Gambierdiscus toxicus, and Prorocentrum lima (Dinophyceae) previously reported. Taken together, we suggest that O. cf. ovata is able to grow faster than the other benthic dinoflagellates in waters of high temperature and salinity. The physiological feature probably confers an ecological advantage on O. cf. ovata in the bloom development during warmer seasons in Japan and may be responsible for outbreaks of PTX‐like poisoning in the region especially during the warmer seasons.     

Effect of irradiance, temperature and salinity on growth and toxin production by Nodularia spumigena

The object of this work was to determine, using a full-factorial experiment, the influence of temperature, irradiance and salinity on growth and hepatotoxin production by Nodularia spumigena, isolated from Lake Alexandrina in the south-east of South Australia. Higher levels of biomass (determined as particulate organic carbon, POC), toxin production and intracellular toxin concentration per mg POC were produced under light limited conditions (30 mol m^–2 s^–1) and at salinities equal to or greater than those experienced in Lake Alexandrina. Both highest biomass and total toxin production rates were recorded at temperatures equal to or greater than those of the lake (20 and 30°C). The temperature at which maximum biomass and toxin production was recorded decreased from 30°C for cultures grown at 30 mol m^–2 s^–1 to 20°C when grown at 80 mol m^–2 s^–1. In contrast, intracellular toxin per mg POC was highest at the lowest growth temperature, 10°C, at both 30 and 80 mol m^–2 s^–1. It appears that the optimum temperature for biosynthetic pathways used in the production of toxin is lower than the optimum temperature for those pathways associated with growth. Intracellular toxin levels were higher in cells cultured at 10°C/30 mol m^–2 s^–1 whereas the majority of the toxin was extracellular in cells grown at 30°C/30 mol m^–2 s^–1. This implies that the highest concentration of toxin in lake water would occur under high temperature and high irradiance conditions. Individual environmental parameters of salinity, irradiance and temperature were all shown to influence growth and toxin production. Notwithstanding, the overall influence of these three parameters on toxin production was mediated through their effect upon growth rate.     

温度、盐度及其互作效应对吉富罗非鱼血清IGF-I与生长的影响

采用中心复合试验设计和响应曲面分析方法,在实验室条件下,探讨了温度(18-37℃)、盐度(0-18)及其互作效应对吉富罗非鱼幼鱼血清IGF-I、生长和饲料效率的影响,并且分析了血清IGF-I与生长、饲料效率的关系.整个试验持续8周.结果表明,温度的一次与二次效应对血清IGF-I、生长和饲料效率有显著影响,盐度的一次与二次效应对血清IGF-I和生长有显著影响.高温与高盐环境会降低罗非鱼的生长与饲料效率.血清IGF-I随水温的上升呈先上升后下降的变化;在等渗点附近,罗非鱼血清IGF-I水平较低.血清IGF-I与生长和饲料效率具有相关性,血清IGF-I水平较高时,特定生长率和饲料效率均较高.温度和盐度的互作效应对血清IGF-I、生长和饲料效率无显著影响(P＞0.05).温度和盐度分别为28.5℃和8.4时,特定生长率和饲料效率同时达到最优值,为2.29％/d和0.82,其可靠性为0.937.低盐环境可以提高罗非鱼的生长与饲料利用,血清IGF-I水平的升高有助于增强罗非鱼渗透调节能力.     

温度、盐度对海月水母碟状体生长及存活的影响

海月水母为我国近海主要大型灾害水母种类之一,当自然环境适宜其生长与繁殖时,易出现暴发性的增殖现象,严重破坏了我国近岸海洋生态系统的稳点与平衡。采用实验生态学方法,研究了温度(2.5、5、7.5、10、15、20、25、27.5、30℃)和盐度(15、20、25、30、35、40)对海月水母碟状体存活与生长的影响,实验共进行30d。结果显示,在实验设置的温盐范围内,温度、盐度均显著影响碟状体的存活与生长。在盐度15-35条件下,海月水母碟状体可以在温度2.5-25℃存活,在15-25℃范围内可正常生长;在温度20-25℃和盐度20-30条件下适宜海月水母碟状体生长,其中温度20℃和盐度25条件下海月水母碟状体特定生长率达到最大。与盐度相比,温度对碟状体的影响较大,在盐度15-35条件下,随着温度的升高,碟状体的伞径逐渐增大,其碟状体形态向水母体形态的转变速度加快。在达到临界点25℃时,若继续升高温度,碟状体的生存率与生长率显著下降。温度与盐度对海月水母碟状体的生存与生长具有明显的交互效应,碟状体在实验过程中表现出在较低温度条件下提高了对较高盐度的适应性。研究表明,温度、盐度的变化显著影响碟状体的生长与存活,直接导致碟状体种群数量变动,进而影响成熟水母体种群数量。结论为进一步探索大型水母暴发的生态环境机理提供重要科学依据。     

Digestion of zooplankton in the alimentary tract of vendace (Coregonus albula) larvae

The degradation of zooplankton eaten by vendace larvae was investigated by cutting their tubiform alimentary tract into four quarters and analysing the contents separately. Soft-bodied rotifers were found to degrade and become indistinguishable in the anterior part of the alimentary tract, while cladocerans and copepods could still be identified in the posterior part. Assessing the diet of a larva on the basis of its whole alimentary tract contents was found to give biased results. More reliable estimates of the proportions of zooplankton taxa in the diet could be achieved from the first quarter of the alimentary tract.     

Comparative physiological studies on the growth of cryptic species of Bostrychia intricata (Rhodomelaceae,Rhodophyta) in various salinity and temperature conditions

Inter‐ and intra‐specific physiological variations of intertidal macroalgae have been well investigated. However, studies on physiological responses of cryptic algal species have been poorly documented. Bostrychia intricata is a widespread marine red alga in the Southern Hemisphere, and has many cryptic species. We investigated the effect of different salinities and temperatures on the specific growth rate of three cryptic species (N2, N4 and N5) of B. intricata from New Zealand. Our data indicated that all cryptic species grew at the full range of salinities and temperatures tested, but exhibited a significant difference in their specific growth rates. Cryptic species N4 had a higher growth rate than the other two cryptic species under all experimental conditions, whereas cryptic species N2 occasionally showed a higher growth rate than cryptic species N5 at high salinities and lower temperatures. The distinct physiological properties of these cryptic species may explain their distribution pattern (a wider distribution of cryptic species N4 than N2 and N5) in New Zealand. The physiological divergence between the cryptic species could be related to their levels of evolutionary divergence, with more similar physiology between cryptic species, which share a more recent common ancestor (N2 and N5). Our findings underline that morphologically indistinguishable cryptic algal species are different in many other aspects and are truly independent entities.     

Effects of egg composition and prey density on the larval growth and survival of lake whitefish (Coregonus clupeaformis Mitchill)

Eggs were collected from two stocks of lake whitefish, Coregonus clupeaformis , in Lakes Michigan and Huron to assess the effect of egg composition and prey density on larval growth and survival. Egg composition parameters including wet weight (mg egg⁻¹), dry weight (mg egg⁻¹), percent water, total caloric content (cal egg⁻¹), caloric density (cal egg⁻¹), percent lipid content, and total lipidcontent (mg egg⁻¹) were measured. Fish hatched from six parental females in each stock were fed one of four rations (0, 18, 24, 50 brine shrimp larva⁻¹ day⁻¹) after yolk sac absorption. Length at hatch, endogenous growth, exogenous growth, and survival were measured during a 42-day laboratory experiment. Length at hatch of larvae was positively related to egg caloric content ( r ²=0.780). Endogenous growth for lake whitefish larvae was positively related to percent lipid content ( r ²=0.896) and total egg lipid content ( r ²=0.876) of parental females. Exogenous growth and survival of larval lake whitefish was positively related to prey availability. Larval fish growth was accurately modelled ( r ²=0.973) as a function of prey abundance using a threshold-corrected hyperbolic equation. These results indicate that both egg composition and prey availability have the potential to influence the growth and survival dynamics of larval lake whitefish significantly.     

温度、盐度对龟足胚胎发育和幼虫生长的联合影响

龟足(Capitulum mitella Linnaeus)在我国主要分布于长江口以南海浪剧烈冲击的暴露型岩相海岸的中、高潮区,是一种颇具养殖潜力和市场前景的新品种。研究温度(24、27、30、33℃)和盐度(28,31,34)对龟足胚胎发育和幼虫生长的协同影响,可为龟足的人工育苗提供依据。结果如下(1):33℃-28温盐度组合胚胎发育时间最短144h,27℃-28温盐度组合胚胎相对孵化率最高。温度与盐度对胚胎发育时间没有显著影响;但温度和盐度对胚胎孵化率有极显著影响,温度与盐度间的交互作用显著。胚胎发育最适宜的温盐度组合是27℃-28。(2):27℃的3个盐度组、30℃-31温盐度组合无节幼虫持续时间最短。在同一盐度条件下以27℃的存活率较高,在同一温度条件下以盐度31的存活率较高,其中以27℃-31温盐度组合的存活率最高;存活率1和存活率2分别高达99.0%、90.7%。27℃-28、27℃-31温盐度组合变态率最高,变态率分别为81.8%、73.7%。34高盐组幼虫的存活率和变态率均很低甚至为零。温度和盐度对幼虫存活率和变态率有极显著影响,两者的交互作用极为显著。综合无节幼虫持续时间、存活和变态情况,27℃-31温盐度组合为幼虫生长发育的最佳组合条件。龟足胚胎发育、无节幼虫的生长和变态对温度盐度的敏感性有所不同,这是由龟足的自身繁殖特点及生活环境决定的。