Spring-spawning Fish Research Articles

Comparison of inshore and offshore fish larval assemblages within the wider Yangtze River estuary (China)

It is hypothesized that fish larvae undertake vertical movements in estuarine waters. To test this hypothesis, a sampling period was selected during times when many spring-spawning fish reach maximum abundance in coastal waters so that spring and summer variations in larval fish assemblages could be determined in the Yangtze River estuary. Six oceanographic surveys were conducted across the salinity gradient of an inshore (freshwater) and offshore area (brackish intersection) during spring (May) and summer (August) between 2010 and 2012. The fish larval community was dominated by species of Engraulidae, Gobiidae, Champsodontidae and Mugilidae. The pre-flexion and flexion larval stages of euryhaline marine species, which are dependent on estuaries as nursery areas, were common. The brackish and marine larval assemblage was the most abundant with taxa such as Coilia mystus and Engraulis japonicus accounting for more than 57.3% of the total catch. Spatial differences in the taxonomic composition of larval fish assemblages were evident between the inshore and offshore areas. Additionally, the Yangtze River runoff regulatory functions as affected by the Three Gorges Reservoir operational mode (hydrological alternating operations) showed weak influences on fish and habitat environments. Low salinities from high freshwater inflow limited bay anchovy production in the inshore area.

Changes in the species composition and abundance of young-of-the-year fishes in the upper Volga stretch of the Kuibyshev Reservoir during the period of 1991 to 2009

The species composition and abundance of young-of-the-year fishes have been analyzed in catches made in the upper Volga stretch of the Kuibyshev Reservoir between 1991 and 2009. It has been found that the juvenile abundance of roach and blue bream has decreased, while that of perch, silver bream, and spined loach has increased, with young-of-the-year juveniles of common rudd, tubenose goby, round goby, and black-striped pipefish appearing in catches. The results of the study show that, against the background of juvenile population decline in many spring-spawning fish species, the abundance and species diversity of young of the year in summer-spawning species has increased during the observation period.

Identification of individuals born in different spawning seasons using otolith microstructure to reveal life history of Neosalanx taihuensis

Otolith microstructure was used to distinguish specimens of Neosalanx taihuensis born in spring and autumn. Increment width during the early life stage was significantly narrower for spring-born than autumn-born juveniles, and the frequency distributions of the width of the first 5 increments were distinctive and diagnostic. Otolith growth trajectories and frequency distribution of the first 5 increments of spring-spawning adults displayed similar patterns to spring-born juveniles. Otolith growth trajectories of autumn-spawning adults were intermediate between those of spring- and autumn-born juveniles, and the frequency distribution of the width of the first 5 increments showed two modes, one similar to spring-born juveniles and the other similar to autumn-born juveniles. Populations of N. taihuensis have previously been shown to be dominated by spring-spawning fish. Thus, the putative life history of N. taihuensis can be summarized as: (1) a small part of the spring-born fish mature and spawn in autumn of the year of their birth, (2) the majority of the spring-born cohort matures and spawns in spring of the next year, and (3) offspring of the autumn-born fish mature and spawn in autumn of the following year. This stock-structure information should be considered in fisheries management for this species.

Does the zooplankton prey availability limit the larval habitats of pike in the Baltic Sea?

The objectives of this study were to (1) investigate whether the availability of suitable zooplankton prey limits the distribution of the coastal larval areas of pike ( Esox lucius) in two archipelago areas of the northern Baltic Sea and (2) compare the availability of zooplankton prey in spring between different types of coastal littoral habitat. According to the results, reed belt habitats formed by Phragmites australis constitute hot spots for zooplankton prey in the coastal ecosystem. During the spring, reed-covered shores of the inner archipelago maintained more than 10 times higher densities of copepods and cladocerans, the preferred prey for larval pike, compared to the other studied shores. Temperature conditions were also most favourable in the reed belt habitat. Thus, the reed belts of the inner and middle archipelago were shown to form the best habitat for larval pike in the coastal area of the northern Baltic Sea, and this was also the only habitat where pike larvae were found. Our results suggest that the poor survival and recruitment of pike in the outer archipelago, however, cannot exclusively be explained by sub-optimal feeding conditions of the larvae. There are also other important factors, presumably connected to the exposure to the open sea, that affect the distribution of the pike larvae. Our results, however, highlight the importance of sheltered coastal reed belt shores as reproduction habitat for spring-spawning fish in the northern Baltic Sea. Further, this study disproves the assumption that the seaweed bladder wrack ( Fucus vesiculosus) forms a reproduction habitat for pike in the coastal area.

Two spawning stocks of icefish Neosalanx taihuensis revealed from annual reproductive cycle analyses

Neosalanx taihuensis were sampled from the Tian-e-zhou Oxbow from March 2006 through November 2007. Two separate spawning seasons were identified based on the annual reproductive cycles of the females, designated as the autumn-spawning season and the spring-spawning season. Lifespan of the offspring of the spring-spawning fish was 1 year, with them dying after the subsequent spring spawning. Autumn-spawned females seem to be the offspring of the spring-spawning fish, based on monthly changes in the length-frequency distributions. Spring-mature females had higher absolute fecundity, gonadosomatic index, and relative condition factor in 2007 than in 2006. Relative condition factor of the immature female offspring of spring-spawning fish was higher in 2007 than in 2006, portending a further increase in reproductive investment during the spring spawning of 2008. The increasing reproductive investment suggests that the population of N. taihuensis in the Tian-e-zhou Oxbow may be recovering from its recent decline.

Dispersal patterns of the eggs and larvae of spring-spawning fish in the Irish Sea, UK

Many marine species produce pelagic propagules which, because of their life-history characteristics and the local hydrodynamics, can disperse considerable distances from the point of release. Distances travelled are affected by factors such as: release time and location, egg and larval stage duration, local environmental conditions and active swimming and settlement behaviours. Understanding such dispersal patterns is important for the design of effective ecosystem-conservation strategies. We used a regional scale, coupled physical-biological model for the Irish Sea to simulate the possible dispersal of eggs and larvae of five species of fish with contrasting early life histories (cod Gadus morhua, plaice Pleuronectes platessa, witch Glyptocephalus cynoglossus, sprat Sprattus sprattus and pogge Agonus cataphractus). The hydrodynamic model was forced with meteorological data for 1995, a year when extensive plankton surveys were conducted in the Irish Sea. A particle tracking method featuring particle release (spawning) and species-dependent particle development and behaviour was then run based on flow and temperature fields from the hydrodynamical model. Modelled larval distributions and settlement areas corresponded favourably with observations from field sampling. The settlement destinations (or onset of shoaling for sprat) were affected both by their initial spawning location and by the species-specific development rates and behaviours coded into the model. Eggs and larvae typically remained within 160 km of their spawning origin, although a minority travelled up to 300 km. Even in a relatively enclosed sea such as the Irish Sea, fish eggs and larvae can be dispersed over 100s of km. This provides a major challenge for the design of effective spatial management strategies if it is necessary to protect a species across its life-history stages. Further progress in the design of effective conservation measures for species or communities will need an integrated approach taking account of key aspects of early life history and behaviour.

Overwintering ability of young-of-the-year bluefish Pomatomus saltatrix: effect of ration and cohort of origin on survival

Bluefish Pomatomus saltatrix have experienced declines in recruitment and adult abun- dance along the US East Coast since the mid-1980s. At the onset of winter, young-of-the-year (YOY) bluefish exhibit a multimodal size distribution including larger, spring-spawned fish (spring cohort) and smaller, summer-spawned fish (summer cohort). Declines in the adult stock appear to coincide with declines in recruitment success of the summer cohort. We investigated the hypothesis that poor recruitment success of the summer cohort results from size-selective winter mortality. Winter meso- cosm experiments were conducted to examine the effects of cohort of origin (spring vs. summer) and food availability (fed vs. unfed) on winter survival of YOY bluefish. Spring fish entered winter with sig- nificantly greater lipid reserves than summer fish. When fed, both cohorts stored lipids during late fall, depleted lipid reserves during winter, and experienced high overwinter survival. When starved, both cohorts mobilized lipids from multiple depots (liver, viscera, white muscle, red muscle, skin) and sum- mer fish experienced starvation mortality ~6 wk prior to spring fish. Although summer fish were more susceptible to winter starvation than spring fish, their starvation endurance (>90% survival probabil- ity after 120 d) appeared more than adequate to survive natural winter conditions. Interestingly, spring fish suffered a brief mortality event during January when water temperatures dropped briefly below 6°C, suggesting that larger individuals are less tolerant of acute cold stress. The remarkable starvation endurance of summer-spawned bluefish, coupled with their capacity for rapid lipid storage during fall and reduced rates of lipid depletion at low temperatures, implies that members of this cohort are physiologically well-equipped to survive their first winter of life. Our findings are inconsistent with the hypothesis that winter starvation accounts for decreased recruitment of the summer cohort to the western Atlantic stock.

Distribution of Steller sea lions Eumetopias jubatus in relation to spring-spawning fish in SE Alaska

Energetic demands are high for Steller sea lions Eumetopias jubatus during spring, when females are pregnant and lactating and males are preparing for extended fasts on breeding territories. Therefore, we predicted that the distribution of sea lions in SE Alaska in spring would be influenced by the distribution of spring spawning aggregations of high-energy prey species (Pacific herring Clupea pallasii and eulachon Thaleichthys pacificus). The spatial distribution of sea lions during spring reflected the distribution of spawning eulachon in northern Southeast Alaska, particularly in Lynn Canal and along the Yakutat forelands. Haulouts with peak numbers of sea lions in spring were located significantly closer to eulachon spawning sites than haulouts that peaked at other times of year. Some haulouts were occupied only during the eulachon spawning period. The maximum number of sea lions at haulouts in spring was inversely correlated with the distance to the closest eulachon aggregation and was positively associated with the number of eulachon within 20 km. Aerial surveys conducted every 7 to 10 d during March through May in 2002 and 2003 revealed large numbers of sea lions in the water at herring spawning sites in 2002 and 2003; however, there were no significant relationships between the number of herring spawning sites and number of sea lions (except at distances >60 km). The number of sea lions was greater at herring spawning sites in 2003, corresponding to higher herring biomass. Seasonally aggregated, high-energy prey species influence the seasonal distribution of sea lions and may be critical to their reproductive success.

Species assemblages of pelagic fish embryos in the southern North Sea between 1984 and 2000

The occurrence and abundance of the pelagic eggs of southern North Sea spring-spawning fish were analysed between 1984 and 2000. Species number varied between six (1986) and 14 (1999) and was positively correlated with sea surface temperature. With one exception, dab eggs were always the most abundant and usually highly dominant. Ranking of species depended on temperature, but no significant differences in ranking between years was discernible. Although with the increase in temperature in the 1990s a change in species assemblage was evident [species belonging to the boreal-Mediterranean (Lusitanian) group became more apparent in the species assemblage] this did not lead to an increased species diversity (Shannon Index) or a change in other community parameters. It appears that the recent developments regarding spawning stock biomass of commercial North Sea fish is reflected in the declining egg abundance of the respective commercial and larger species (i.e. cod, flounder, plaice) and an increase in abundance of the eggs of small species (i.e. long rough dab, rockling) over the years.

Influence of solar ultraviolet-B on pelagic fish embryos: osmolality, mortality and viable hatch

Eggs of dab (Limanda limanda) and plaice (Pleuronectes platessa) were experimentally exposed to ultraviolet-B (UV-B) radiation in a solar radiation simulator. The experimental design tried to simulate present and future conditions with reference to increased UV-B exposure due to northern hemisphere ozone loss, employing mainly two scenarios, a reduction to 270 (S1) and to 180 (S2) Dobson units (DU) in single or repetitive exposures of 2, 4 or 6 h. Depending on the total dose of UV-B irradiation and the developmental stage, exposed eggs displayed loss of buoyancy as a sublethal effect, as well as increased embryo mortality and reduced viable hatch. In the single exposure experiments only under conditions of 180 DU for 6 h were effects apparent. Double exposure under conditions of 270 DU did not lead to lasting effects. At the sublethal effect level, i.e. loss of buoyancy, considerable photorepair was observed. It was concluded, that under the present general weather conditions in spring and at the present levels of environmental ozone, allowing for a reduction to 180 DU, the embryonic development of North Sea spring spawning fish is not endangered by UV-B radiation.

One Person's Food: How and Why Fish Avoidance May Affect the Settlement and Subsistence Patterns of Hunter-Gatherers

Foraging strategies of modern hunter-gatherers may not accurately model resource use of specialized big-game hunters. Historic accounts from the Northern Plains of North America indicate that utilization of spring-spawning fish when large mammals were fat-depleted was not universally beneficial. Three independent reports from Europeans and Americans show that a sudden switch from a prolonged diet of lean red meat to fish produces symptoms consistent with lipid (fat) malabsorption. It is hypothesized that plains-adapted hunter-gatherers formed their camps in grassland environments and hunted big game throughout the winter The effects of eating lean meat alone were avoided by utilizing fetal and newborn animals and through the use of stored carbohydrate-rich foods. Groups associated with wooded environments wintered along the margins of the winter grazing range. They followed a diverse strategy with opportunistic use of big game and were able to exploit spring-spawning fish. Archaeological remains from 18 sites from the plains, parkland, and forests of Western Canada were used to test these hypotheses. The faunal assemblages, tools, and identifications of lipid residues from pottery vessels were consistent with the proposed strategies.

Recruitment dynamics of bluefish (Pomatomus saltatrix) from Cape Hatteras to Cape Cod, 1973–1995

Recruitment dynamics are complicated in species in which multiple cohorts of young-of-the-year (YOY) are produced each year. Each summer, two cohorts of YOY bluefish (Pomatomus saltatrix), representing fish spawned in spring and summer, recruit to Mid-Atlantic Bight estuaries, but little is known about their interannual variability, environmental forcing, and relative contributions to later life stages. We addressed these questions by examining the distribution and abundance of YOY on the continental shelf of the US east coast in autumn from 1973 through 1995. Abundance on the continental shelf increased in autumn owing to emigration from estuaries. We found clear evidence of two cohorts in autumn length-frequency distributions in most years and used this information to construct cohort-specific indices of abundance, which were then compared with relevant environmental variables. Spring-spawned fish dominated the catch in 20 of the years examined. The summer cohort dominated only in 1992. The abundance of the two cohorts was positively correlated, rejecting the hypothesis that dominance of the spring cohort is the result of cannibalism on the summer cohort. Spring cohort abundance was not correlated with either shelf warming-rate or warm-core ring streamer activity. A strong relationship was found between winds in April and May and the abundance of spring-spawned bluefish, possibly indicating that wind-driven surface flow aids the transport of larvae and/or juveniles across the shelf-slope region. 2000 International Council for the Exploration of the Sea

Effects of Photoperiod Manipulation on Brook Trout Reproductive Development, Fecundity, and Circulating Sex Steroid Concentrations

The goal of this study was to determine the feasibility of conducting reproductive studies with brook trout Salvelinus fontinalis at times other than the normal fall-spawning period. The timing of sexual maturation, fecundity, and concentrations of serum sex steroids (17-β-estradiol, E2; and testosterone, T) in brook trout held under a normal photoperiod were compared with those in brook trout held under an altered photoperiod (initiated in early September). Fish held on a constant long photoperiod (18 h light: 6 h dark) did not reach sexual maturity during the normal fall-spawning time. When these fish were subsequently subjected to a 16-week accelerated photoperiod reduction from 18 h light/d to a day length of 8.5 h, the males and females matured in 8 and 13 weeks, respectively, and spawned successfully in April and May. Overall viability of embryos from this spring spawning was slightly lower than the average viability of control embryos from previous studies with fall-spawning fish in our laboratory; however, hatchability of viable embryos was similar for the spring-spawning fish and those from previous studies. Hormonal profiles of E2 and T were similar for both females and males in fall- and spring-spawning brook trout. These studies demonstrate that photoperiod alterations can be used to manipulate brook trout reproductive cycles for the purpose of conducting studies at times other than the fall.

Correlated Variations in Abundance, Size, Growth, and Loss Rates of Age-0 Bluefish in a Southern New England Estuary

Abstract Age-0 bluefish Pomatomus saltatrix were widely distributed and seasonally abundant in shallow beach habitats of Narragansett Bay, Rhode Island. Based on length-frequency data that were polymodal in some years, these age-0 fish comprised spring- and summer-spawned cohorts. Cohort-specific measures of abundance, growth, total mortality and emigration, and size were determined for 1982–1992. In all years, spring-spawned fish dominated the catch from at least July to September. For this cohort, annual abundance varied by an order of magnitude, growth ranged from 0.9 to 2.1 mm/d, total mortality and emigration rates were between 0.2 and 2.8%/d, and mean length on October 1 ranged from 164 to 248 mm fork length. Spring-spawned fish were about twice as large as summer-spawned fish by October. Summer-spawned fish also occurred less frequently and in lower abundance. These findings confirm that Narragansett Bay is an important nursery for bluefish, and that the trend toward declining annual abundance meas...

Acid stress and extinction of a spring-spawning fish population

Investigation of Heeney Lake, 21.7 ha, revealed a small population of white sucker, Catostomus commersoni. Only four age-classes were represented in this normally abundant and long-lived species. By 1984 only one new age-class had been recruited into the population. As these fish spawned in the outlet stream in early spring, the potential toxicity of these waters was assessed at two snow-melt events. Rainbow trout, Oncorhynchus mykiss, of hatchery origin were held in the outlet stream as pH declined from 6.5 to 4.7 during a snow melt, late February. Trout showed a loss of 19% in plasma Na and 24% in Cl concurrent with gill Al concentration increasing from 10 to 250 μg'g−1 dry wt. At the mid-April snow melt, pH fell to 4.1, and rainbow trout held in the outlet showed a decline in plasma sodium of 42% and gill Al increased from 10 to 415 μg'g−1 dry wt. Control rainbow trout held in Harp L. at pH 6.3 showed no significant change in plasma and muscle ion concentrations, or in gill Al concentration.

Spawning Season and First-Year Growth of Adult Bluefish from the New York Bight

Bluefish Pomatomus saltatrix in the western north Atlantic spawn in the South Atlantic Bight in spring and the Mid-Atlantic Bight in summer. We performed back-calculations to length at age 1 from scales of fish captured during June–September 1986 and 1987 from Long Island, New York, to determine if spring- and summer-spawned fish could be identified among summer-spawning adults captured in the New York Bight. Analysis of gonads confirmed that the summer spawning season off New York is a temporally distinct event occurring from late June to late August, with peak activity in July. All fish used for back-calculations were in spawning condition, and most had lengths at age 1 characteristic of a spring birth date (mean length, 26.5 cm). This observation does not support the hypothesis that spring and summer spawners are two different stocks of fish. Contemporary stocks of adult bluefish along the mid-Atlantic coast may consist largely of spring-spawned fish.

Breeding habits of Windermere charr, Salvelinus willughbii (Günther), and their bearing on speciation of these fish

Breeding habits of Windermere charr, <i>Salvelinus willughbii</i> (Günther), and their bearing on speciation of these fish

The Seasonal Abundance and Distribution of the Pelagic Young of Teleostean Fishes Caught in the Ring-trawl in Offshore Waters in the Plymouth Area. Part II

Data are given on the abundance of post-larval stages of teleostean fish in half-hour oblique hauls with the 2-metre stramin ring-trawl taken at weekly intervals at a position two miles east of the Eddystone lighthouse during the years 1930 to 1934 inclusive.The seasonal composition of the catches is considered and it is shown that there is a gradual change over from the young of northern species of fish to those of more southern species as the summer advances. The relation between the spawning times of closely related species appears usually to be a function of their geographic distribution.The period of maximum abundance of post-larvæ of spring-spawning fish occurs at different times in different years and this difference may be as much as a month. An apparent correlation between the times of abundance of young whiting and the previous temperature of the water has been shown.