Spawning Dates Research Articles

Distribution of egg strands of perch (Perca fluviatilis L.) with respect to depth and spawning substrate

The distribution of egg strands of perch Perca fluviatilis was studied in relation to water depth and spawning substrate during late April and early May 2007 in Chabařovice Lake, Czech Republic, using SCUBA divers and parallel transects. The depth distribution of egg strands differed significantly between the two sampling dates, being much deeper in early May compared to late April. Perch used at least seven different spawning substrates of which the most important were curly pondweed Potamogeton crispus, worm weed Artemisia sp. and common reed Phragmites communis. However, while living submerged vegetation, although more abundant, was generally avoided, dead submerged vegetation was strongly preferred. It appears that dead vegetation is an ideal spawning substrate for perch since placement of the egg strands over those hard, complex three-dimensional structures ensures that the eggs remain well oxygenated 24 hours a day. Factors with significant influence on the distribution of egg strands were as follows (in order of decreasing influence): depth of deposition, type of spawning substrate, date of spawning and temperature at the depth of deposition.

Factors affecting chilled storage of zebrafish ( Danio rerio) embryos

Chilled storage of zebrafish embryos was investigated at a temperature that arrests embryonic development as this technique might offer interesting practical applications. Five parameters played an important role for chilled storage: (a) storage temperature, (b) development stage of embryos, (c) storage solution (extender), (d) postchilling treatment, and (e) inhibition of growth of microorganisms by antibiotics. The optimal chilling temperature was 8 °C. Prim-5 stage (24 h postfertilization [hpf]) and prim-25 stage (36 hpf) embryos had similar high chilling resistance and could be chilled for 33 h without a loss in viability. Five-somite stage (12 hpf) embryos had a lower chilling resistance and could be chilled only for 14 h without a loss in viability. After longer incubation periods, the viability started to decrease. Under these conditions, chilling in physiologic saline solutions was superior to that in water. Fifty percent of the prim-5 stage and prim-25 stage embryos survived for 41 h at 8 °C in water but for 46 h in physiologic saline solution. A similar effect was observed for 5-somite stage embryos (50% survival rate in water, 28 h; 50% survival rate in physiologic saline solution, 35 h). When embryos were incubated in physiologic saline solution instead of water in the postchilling phase, the embryo viability was positively affected, too. Also, supplementation of the storage solution with antibiotics (penicillin and streptomycin) increased the viability of chilled embryos. In summary, the current study shows that chilled storage of zebrafish embryos is possible for sufficiently long periods to synchronize the development of embryos deriving from different spawning dates or to delay the development for experimental purposes. To prolong the storage periods, further development and standardization of the methodology is necessary.

Coral spawn timing is a direct response to solar light cycles and is not an entrained circadian response

Broadcast spawning corals release gametes into the oceans with extraordinarily accurate timing. While the date of spawning is set by the lunar cycle, the hour/minute of spawning is set by the solar cycle. In this report, we describe experiments that test whether the time of spawning is regulated by an entrained biological clock or whether it is directly controlled by the solar cycle. Montastraea franksi samples were collected on the morning of the predicted spawning. Fragments from colonies were kept under three different lighting conditions and spawning monitored. The three conditions were sunset times of 0, 1 or 2 h earlier than normal. Fragments from the same colony spawned differently under these three conditions, with an early sunset causing a corresponding early shift in spawning. These results indicate that spawn timing is not controlled by a circadian rhythm and that it is directly controlled by local solar light cycle.

Influence of temperature on the spatial distribution of first spawning dates of the common frog (Rana temporaria) in the UK

AbstractBetween 1998 and 2007, the UK Phenology Network collected nearly 70 000 records of the first spawn dates of the common frog Rana temporaria. Annual national mean dates varied by more than 2 weeks and were closely related to January–March temperatures. A 1 °C increase in Central England Temperature advanced national mean spawning by 5.1 days. The temporal pattern of spawning records varied between years; sometimes unimodal in form, sometimes multimodal, seemingly associated with steady or erratic rises in spring temperatures, respectively. Spatial patterns of frogspawn were similar in different years, the earliest records occurring in the southwest with records progressively later in the north and east. On average, 100 km of eastwards progression took 7.4 days and 100 km of northwards progression took 4.7 days. A composite map for the 1998–2007 period is constructed and compared with an earlier published map based on data 60 years previously. The similarity and dissimilarity of these two maps is discussed; the general progression pattern of frogspawn phenology is similar but an advance of a 10‐day contour category is apparent. We anticipate further advances of frog spawning dates in the future and an increase in the numbers of pre‐January 1 records of frog breeding.

Aspects of gametogenesis, oocyte morphology and maturation of the lugworm Arenicola marina (Annelida: Polychaeta) in relation to commercialised procedures to extend the breeding season

Environmental manipulation is a common method of extending the spawning season of aquaculture species including the polychaete worm Arenicola marina. Temperature synchronises autumn spawning populations and so its manipulation was used to advance and delay spawning. Females were exposed to a minimum period of 3 weeks at 5 °C in conjunction with the injection of prostomial homogenate to induce spawning up to 4 weeks prior to the natural spawning date. We also maintained individuals at 15–17 °C starting 4 weeks prior to, and then continuing after the natural spawning date, delaying spawning for up to 4 months. Both sexes can be manipulated, but males suffered higher mortalities and a greater rate of spontaneous spawning within the tanks. In ‘advanced’ females, mean oocyte diameters (measured in September, one month prior to spawning) were significantly larger and more homogenous compared to ambient individuals, whilst ‘delayed’ females produced a second cohort of oocytes approximately 8 weeks into the treatment. Delaying and advancing spawning induced significant changes in the ultrastructural morphology of prophase and metaphase oocytes, and delayed prophase oocytes showed a significant increase in the number with cracks on the surface of the vitelline membrane. Although, SDS-PAGE and Western blots confirmed that Maturation Promoting Factor (MPF) activity was not different from ambient controls, there were significant changes in MPF activity levels (measured by histone kinase activity) in manipulated oocytes. A. marina has the plasticity for spawning to be delayed and advanced by a number of months; this is essential for the continued development of aquaculture of this species. However, the maturational ability of the oocytes is compromised and this may have significant implications for production and quality of the offspring from manipulated individuals.

Growth and secondary production of an eventual reef fish during mangrove residency

Hierarchical data frameworks have been proposed to determine the relative value of fish habitats. Although conceptually accurate, judgments as to which habitat is more “essential” are limited by a lack of available information. This work provides much needed growth and production rates for gray snapper ( Lutjanus griseus), an ontogenetic habitat shifting reef fish, during mangrove residency. Ages were estimated using modal progression analysis of length–frequency distributions coupled with a biologically-realistic spawning date. Growth estimates place age-1 L. griseus at 155 mm (TL), age-2 at 243, and age-3 at 302 mm. These size-at-age estimates are consistent with otolith-based studies and are a natural extension of linear growth models for early juveniles. Lutjanus griseus primarily use southeastern Florida mangrove shoreline habitats for approximately 2 years between 0.86 and 2.84 years of age. Corresponding production:biomass ratios for these cohorts were 1.51 and 0.90. While these values are similar to other estimates for fishes inhabiting vegetated coastal wetlands in North America, they are much less than new estimates from a Bahamian mangrove creek system. These new data highlight important differences between the habitat value of mangrove shorelines of continental (low-relief) and island (high-relief) systems.

Reproduction of mykiss Parasalmo mykiss in the Kol river (Western Kamchatka) and its controlling factors

For the first time, special traits of the reproduction of mykiss Parasalmo mykiss in Kamchatka are studied: dates of spawning, localization, topography and hydrology of spawning grounds, structure and fractional composition of ground of redds, duration of incubation and larval period, and thermal conditions. Possibilities of reproduction of mykiss are constrained by a narrow range of variation of spawning conditions. Spawning occurs only in tundra rivers and tributaries. The principal factor limiting reproduction of mykiss is temperature, namely a rapid warming of water in May and attaining of a necessary sum of degree-days (over 500, from the middle of May until the middle of July) during spawning and the period of incubation. Presence of water bodies of the tundra type with their special thermal conditions predetermine a possibility of reproduction of mykiss in Kamchatka and its present-day comparatively narrow area in Asia.

Long-Term Trends toward Earlier Breeding of Japanese Amphibians

Recently, declines in amphibian populations all over the world have been reported. Global warming has the potential to become one of the most important causes for those declines, because reproductive activities of amphibians are affected severely by temperature and rainfall. It has been reported that climate warming has promoted a long-term tendency toward earlier breeding among amphibian populations in Europe and North America. However, some studies have not supported such a long-term change in the timing of amphibian breeding in those areas. We analyzed long-term data sets (12- to 31-year period) on the date of first spawning for four populations of three Japanese amphibians (Hynobius tokyoensis, Rana ornativentris, and Rhacophorus arboreus) in the suburbs of Tokyo and detected a significant trend toward earlier breeding in all populations examined. We also detected that the date of first spawning was correlated strongly with the mean monthly temperature just before the breeding season for each population examined. Given that the long-term trend of warming in the study district was significant, our investigation demonstrated that climate warming has affected the timing of breeding in at least some species or populations of amphibians in East Asia.

Characteristics of Calanus finmarchicus dormancy patterns in the Northwest Atlantic

Abstract Johnson, C. L., Leising, A. W., Runge, J. A., Head, E. J. H., Pepin, P., Plourde, S., and Durbin, E. G. 2008. Characteristics of Calanus finmarchicus dormancy patterns in the Northwest Atlantic. – ICES Journal of Marine Science, 65: 339–350. Demographic time-series from four fixed stations in the Northwest Atlantic Ocean demonstrate variable timing of entry into and emergence from dormancy in subpopulations of the planktonic copepod Calanus finmarchicus. A proxy for timing of entry was established as the date each year when the proportion of the fifth copepodid stage (CV) in the subpopulation rose to half its overall climatological maximum CV proportion at that station. The proxy for timing of emergence at each station was set as the first date when adults were more than 10% of the total abundance of copepodid stages. An alternate emergence proxy date was determined by back-calculating the spawning dates of the first early copepodid stages appearing in spring, using a stage-structured, individual-based model. No single environmental cue (photoperiod, surface temperature, or average surface-layer chlorophyll a concentration) consistently explained entry or emergence dates across all stations. Among hypotheses put forward to explain dormancy in Calanus species, we cannot eliminate the lipid accumulation window hypothesis for onset of dormancy or a lipid-modulated endogenous timer controlling dormancy duration. The fundamental premise of these hypotheses is that individuals can only enter dormancy if their food and temperature history allows them to accumulate sufficient lipid to endure overwintering, moult, and undergo early stages of gonad maturation.

Fecundity, Age and Growth, and Diet of Fundulus diaphanus (Banded Killifish) in Presque Isle Bay, Lake Erie

Abstract Fundulus diaphanus (banded killifish) were the most abundant fish collected in the shallow water areas of Presque Isle Bay, making up 86% of fish collected. Peak spawning dates based on gonadosomatic index and ovary observations were July 9, 2003 and July 18, 2004. Females became sexually mature at age 1. During 2004, the majority of spawning occurred over a 20-day period between July 9 and July 29. Total fecundity increased with both size and age, and the mean total number of eggs produced was 526 ± 37 at age 1 (67 mm ± 1.8), 744 ± 38 at age 2 (79 mm ± 2.4), and 1062 ± 43 at age 3 (93 mm ± 4.1). Based on comparison of the total number of eggs and number of eggs with yolk contained within ovaries, three clutches of eggs may be released during each spawning season. Diets were similar between summer and fall; banded killifish fed almost exclusively on cladocerans and benthic macroinvertebrates.

Variation in reproductive success and effective number of breeders in a hatchery population of steelhead trout (Oncorhynchus mykiss): examination by microsatellite-based parentage analysis

Conservation programs that release captive-bred individuals into the wild to mix with naturally produced individuals are an increasingly common method of supporting or enhancing weak or reduced populations that otherwise may not be self-sustaining. Captive and supportive breeding can be important conservation tools for species with small or declining populations; however, in the case of hatcheries producing salmonid fishes, detailed evaluation of spawning programs is rare. We examined variation in reproductive success, measured by adult offspring production, from three parental generations of hatchery-bred steelhead trout (Oncorhynchus mykiss) using an exclusion-based method of genetic parentage assignment. Reproductive success varied greatly among individuals (especially males) and was correlated with fecundity and maternal spawning date. Estimates of egg to smolt survival for the population as a whole among years ranged from 64% to 95%, marine survival ranged from 0.32% to 2.30%, and the number of adults produced per female ranged from 0 to 18 and the number of adults produced per male ranged from 0 to 32. The effective number of breeders ranged from 11% to 31% of the census population size for that brood year. These ratios fell within estimates from estimates of Ne/N in chinook (O. tshawytscha) and rainbow trout (O. mykiss) hatchery populations.

Induced Spawning and Egg Quality Evaluation of Red Snapper, Lutjanus campechanus

Abstract Brood red snapper, Lutjanus campechanus, were captured from the wild and induced to ovulate by human chorionic gonadotropin (hCG) injection; eggs and sperm were manually stripped; and the eggs were artificially fertilized. Eggs were evaluated by the following egg quality parameters: buoyancy, fertilization, egg size, and oil globule size and number. The relationship of these egg quality parameters and brood characteristics (female size, fecundity, time of year, and response time to ovulation) to 36 h posthatch larval survival was considered. Injection of wild‐caught red snapper females with 1100 IU/kg of hCG resulted in 75% of the females ovulating. The average fecundity was 343,377 ± 30,805 eggs/kg, with a mean percent fertilization of 79.0 ± 1.74%. The mean percentage of floating eggs per spawn was 91.8 ± 1.75%. Mean egg diameter for floating eggs was 778.3 ± 2.09 μm, with a mean oil globule diameter of 117.5 ± 1.53 μm. Brood‐related characteristics were a better predictor of larval survival than postovulation egg characteristics. The percentage of floating eggs in a spawn was not correlated to larval survival. Spawns with eggs having a single oil globule had a similar larval survival as those eggs where multiple globules were common. No clear relationships were found for any one factor and larval survival, but rather a combination of factors was more predictive of survival, most notably spawn date, fecundity, and response time following hCG injection.

Latitudinal gradients in onset date, onset temperature and duration of spawning of roach

Onset date, onset temperature and duration of spawning of roach Rutilus rutilus were related to latitude (40–66° N) and altitude (−1–825 m) based on data from the literature over the whole geographic distribution of roach. Onset date was positively and duration was negatively correlated with latitude, while no correlation was found between onset temperature and latitude. No significant correlations were found between any of the analysed variables of spawning and altitude, probably because most of the analysed populations were below 300 m altitude.

Growth of larval Pacific anchovy Engraulis japonicus in the Yellow Sea as indicated by otolith microstructure analysis

Larval Pacific anchovy Engraulis japonicus were sampled from coastal waters off the central west coast of Korea from June to November 1996. Using otolith microstructure analysis (daily growth increments), three cohorts (spring, early summer and late summer) were distinguished based on backcalculated spawning dates. Growth rates differed between cohorts, with higher growth rates for late‐summer cohorts than either the spring or early‐summer cohorts. Growth rate was positively related to surface water temperature, with an optimum temperature range of between 20 and 26° C occurring during the late summer (late July through to mid‐September). The study highlights that early growth rates of Pacific anchovy are dependent on ecosystem (particularly water temperature) attributes during early life.

Short-term stock assessment of Loligo gahi at the Falkland Islands: sequential use of stochastic biomass projection and stock depletion models

Abstract Roa-Ureta, R. and Arkhipkin, A. I. 2007. Short-term stock assessment of Loligo gahi at the Falkland Islands: sequential use of stochastic biomass projection and stock depletion models – ICES Journal of Marine Science, 64, 3–17. Two short-term stock assessment models are combined to examine the pre-season, in-season, and post-season dynamics of the Loligo gahi fishery off the Falkland Islands over four consecutive fishing seasons. A stochastic biomass projection model (SBPM) projects a pre-season survey-based biomass estimate from the date of the survey to the start of the season. A stock depletion model (SDM) assesses in-season biomass from commercial daily catch-and-effort data. The SBPM projects the SDM biomass estimate at the end of the season to a post-season date of spawning. Combining the SBPM and the SDM helps to clarify the spatio-temporal functioning of the stock and to assess the comparability of survey- and fishery-based estimates of biomass. For the first 2005 season, projected length frequencies indicate two pulses of recruitment onto the fishing grounds. Survey-based projections of biomass were lower than equivalent fishery-based estimates. Over two surveys, the sex ratio was balanced, suggesting full recruitment of both sexes onto the fishing grounds, and the ratio of survey-projected to fishing-estimated biomass was constant. This constant is interpreted as a scaling factor between survey biomass and absolute biomass.

Long-term variation in dates of mass spawning of cod Gadus morhua callarias (Gadidae) in the southeastern part of the Baltic Sea

Long-term data on the numbers of eggs of cod Gadus morhua callarias in ichthyoplankton and the seasonal variation of their distribution in the Gdansk Deep of the Baltic Sea are considered. The spring peak of spawning was observed for the years 1948–1954 and 1960–1964; the spring-summer peak for 1968–1977; and the summer peak for 1955–1959 and 1995–2001. Maximum egg numbers of cod were recorded from the late 1940s to the early 1950s; minimums were recorded in the late 1980s and the late 1990s. The decrease in the numbers of cod eggs in the ichthyoplankton, in general, coincided with a decrease in the proportion of spawners maturing at the beginning of the season of mass reproduction and a decrease in the oxygen content in the near-bottom layer of the Gdansk Deep. It is suggested that a shift of the spawning peak of cod from spring to summer is related to a decrease in the volume of near-bottom waters providing favorable conditions for the reproduction of this population.

Genetic improvement in coho salmon (Oncorhynchus kisutch). II: Selection response for early spawning date

Phenotypic records of within-year spawning date in two cultivated populations of coho salmon, named as even (n=2272) and odd (n=1347) year classes are analyzed. Both populations were selected for harvest weight and early spawning for four generations, using independent culling levels. Harvest weight was selected using breeding values obtained from an animal model in males and females, while early spawning was selected phenotypically only in females. A post-selection analysis to estimate breeding values in both characters allowed comparison of the phenotypic response (R) and genetic selection response (GR) to selection for early spawning, narrow sense heritability (h2), and genetic correlation with harvest weight (rg). Mean spawning dates were 13 and 15 days earlier after four generations of selection in the even and odd year class, respectively. This represents a phenotypic response to selection of −2.74±0.7 (P=0.03) and −3.23±1.3 (P=0.09) days per generation in the even and odd year classes, respectively. The heritability estimates, by regression of the selection differential on phenotypic change, were h2=1.78±0.37 (P<0.05) for the even year class and h2=1.90±0.42 (P<0.05) for the odd year class. In both cases, calculated values were greater than the highest possible value for heritability (h2=1), which indicates that the response is overestimated due to a positive environmental effect which was not quantified. The estimates of narrow sense heritability using an animal model were high in both populations (even year class h2=0.40±0.05, odd year class h2=0.44±0.06). Breeding value analysis showed the genetic selection response was −0.62 and −1.13 days per generation in the even and odd year classes, respectively. The genetic correlation between spawning date and harvest weight was low in both year classes (even rg=0.25±0.13; odd rg=−0.02±0.24). The genetic selection differentials (GS) were lower in males than in females (even year class GSf=−1.12 y GSm=−0.13; odd year class GSf=−1.46; GSm=−0.36), which reflects selection practiced only on females.

Genetic improvement in Coho salmon (Oncorhynchus kisutch). I: Selection response and inbreeding depression on harvest weight

In this study the genetic response to selection and the effects of inbreeding on harvest weight in two populations (which spawned as even and odd years classes) of Coho salmon are described. Artificial selection was performed using the best linear unbiased prediction (BLUP) of breeding values obtained from an animal model. Both populations were also selected for early spawning date using independent culling levels; these results are presented in a companion paper. The estimation of genetic parameters was based on the phenotypic records of 12,208 animals randomly sampled at harvest time (random group). These fish represented a mean of 64% and 48% of all animals with phenotypic records in the even and odd year classes, respectively. The narrow sense heritability estimated for harvest weight was high and very similar in the two populations, 0.39±0.03 in the even year class and 0.40±0.04 in the odd year class. Due to the mating design, the genetic selection differentials were 2.3 times greater in males than in females. The mean genetic selection response obtained was high in both populations, 383.2 g or +1.26 σ and 302.4 g or +1.23 σ per generation in the even and odd year classes, respectively. This is equivalent, on the average, to an increase in weight of 13.9% per generation compared to the base population, or 10.2% per generation with respect to the difference between successive generations. After the 4th generation of selection the mean inbreeding level was 9.5% in the even year class and 4.4% in the odd year class, which are close to preliminary estimates based on the records of the random group plus a group of animals with high harvest weight (Gallardo, J.A., García, X., Lhorente, J.P., Neira, R., 2004b. Effects of nonrandom mating schemes to delay the inbreeding accumulation in cultured populations of Coho salmon (Oncorhynchus kisutch). Can. J. Fish. Aqua. Sci. 61, 547–553.). The estimated effects of inbreeding depression on harvest weight were negative, but not significantly different from 0 in either the even year class (bf=−7.04 g/ΔF, s.e.=3.9; Mean=4118 g; inbreeding depression per 10% of ΔF was −1.7%; P=0.06) or the odd year class (bf=−4.8 g/ΔF, s.e.=0.33; Mean=3243 g; inbreeding depression per 10% of ΔF was −1.5%; P=0.33). Other programs in salmon have selected for more than one character, however, there are still no estimates of economic weights published in salmon breeding programs, which are necessary to calculate the total genetic merit for these animals.

Natural Egg Mortality and Clutch Size of the Japanese Treefrog, Rhacophorus arboreus (Amphibia: Rhacophoridae)

Embryonic mortality and clutch size of the foam-nesting treefrog Rhacophorus arboreus were observed in early summer of 2000 and 2001 at a small pond in a secondary forest on the campus grounds of Tokyo Metropolitan University. A total of 24 foam nests were monitored from just after spawning. When hatchlings emerged, the foam nests were collected and examined for embryonic mortality and clutch size. Embryonic mortality, averaging 0.233 (0.036–0.616, SD=0.173), varied markedly among nests. Logistic regression showed that the date of spawning had a significant effect on embryonic mortality: the nests constructed late in the season suffered higher mortality. Clutch size varied from 272 to 872 (x̄=522.1, SD=134.0). Multiple regression analysis showed that year and date of spawning had no significant effect on clutch size. A significant correlation was detected between clutch size and height of the nesting position (r=−0.563, P=0.004): those nests constructed higher above the pond water tended to have smaller clutches. Factors affecting egg mortality and clutch size are discussed.

Effects of population size/age structure, condition and temporal dynamics of spawning on reproductive output in Atlantic cod ( Gadus morhua)

In this study, we model daily reproductive output over an entire spawning season for a range of simulated age/size-structured populations of Atlantic cod ( Gadus morhua), which are created under contrasting stock–recruitment and fishing pressure scenarios. An individual-based modelling approach is used to link empirical relationships with flexible reproductive parameters to quantify and qualify the effects that individual female condition and egg quality can have on stock reproductive potential (SRP) and the temporal distribution of reproductive output. The results of this study indicate that, even with a set of steady state populations that have equal spawning stock biomass (SSB), the differences in population structure brought about by a difference of fishing mortality ( F) from 0 to 1.0 will substantially reduce the SRP. Compared to a non-fished population the decline in SRP will range from 48 to 74%, depending upon respective assumptions of egg size on viability. The truncation of population age/size structure due to fishing mortality will also lead to a 4 weeks shorter spawning season and a 2 weeks shift in the date of peak spawning. The effect of low condition of individuals can lead to almost total reproductive failure for the population and the effect of increased condition is dependent upon the population structure in question. Results as such support the view that predictions of recruitment can no longer be based solely as a function of SSB. More careful analysis of the population structure as well as annual dynamics of condition factors and exploration of functional relationships between female characteristics and egg quality are needed to assess and accurately predict survival and the probability of recruitment levels.