Timing Of Spawning Research Articles

Reproductive Aspects of Blue Swimming Crab (Portunus pelagicus) Landed on the South End Coast of East Lombok

This study aims to describe aspects of the reproductive biology of a blue swimming crab (Portunus pelagicus) that landed at the southern end of the coast of East Lombok during the period November 2023 to April 2024. The study used a descriptive design with a quantitative approach to measure and analyze data through direct observation. Data included carapace width, body weight, gonad maturity stages, and gonad somatic index (GSI) of P.pelagicus. The results showed that the male P.pelagicus population was more dominant than females every month. P.pelagicus body weight varied, with significant increases in certain months caused by spawning. Analysis of the relationship between carapace width and body weight showed positive allometric growth, with b values of 3.17 for males and 3.10 for females, indicating that body weight gain was faster than carapace width. The maturity stages of the P.pelagicus gonads were mostly at stages I and II, with a few reaching stages III and IV. The average gonad maturity stages increased from 2.42% in November to a peak of 5,83 % in February, then decreased in the following months. The primary spawning time occurs from December to February, characterized by changes in gonad color and a decrease in the body weight of the P. pelagicus after spawning. Hopefully, this study’s results can positively contribute to the sustainable management of crabs (P. pelagicus).

The potential of oviduct tags and fine-scale acoustic telemetry to reveal the timing and location of spawning in Arctic salmonids (Salvelinus spp.).

Identifying and characterizing spawning locations are paramount for the protection of critical fish habitats but can be challenging, particularly in remote locations. Using the underexplored oviduct-tagging technique, we aimed to identify the timing and location of spawning for wild Arctic char (Salvelinus alpinus) and lake trout (Salvelinus namaycush) in two high-Arctic lakes in Nunavut. Specifically, Innovasea V7 acoustic telemetry transmitters were inserted into the oviducts of 13 Arctic char and 4 lake trout, and the timing and location of tag expulsion were determined using a fine-scale positioning system. Twenty Arctic char and 20 lake trout were also tagged with abdominal V16 transmitters, and 10 of them were paired with the oviduct tags, to further study the behavior of individual fish during the spawning season. Oviduct tags from four Arctic char and one lake trout could be used to assess the timing and location of spawning. Spawning anadromous Arctic char drastically reduced their activity and remained proximate to their presumed spawning location immediately before and for months after spawning. In contrast, a non-anadromous (i.e., freshwater resident) Arctic char and a lake trout showed little to no reduction in activity around presumed spawning events. Because of the highlighted sedentary behavior of inferred spawning anadromous Arctic char implanted with both abdominal and oviduct tags, we could also infer potential spawning based on the behavior of individuals equipped only with abdominal tags. Spawning areas identified via telemetry also aligned well with Inuit knowledge of those lakes. This is the first field study to use acoustic oviduct and abdominal tags coupled with a fine-scale positioning system. Despite a limited success rate of ejection, the study reveals the strong potential of the method to study spawning habitat and timing, particularly in remote areas.

Stock identification of sympatric Atlantic cod populations in the Gulf of Maine and mixed stock fishery analysis using otolith-based techniques

Sympatric populations of Atlantic cod with distinct spawning times in winter and spring have been identified within the Gulf of Maine. A new western Gulf of Maine stock assessment unit in U.S. waters lumps winter and spring spawning populations into a single stock unit and future monitoring and assessment of their abundance will require mixed stock analysis. The goal of this study was to evaluate the utility of otolith-based stock identification techniques to discriminate spawning populations. Significant differences in otolith structure and microchemistry were identified between winter and spring spawners with the highest degree of classification accuracy based on both features. Mixed stock analysis applied to fishery samples of unknown origin indicated the contemporary (2015-2016) commercial fishery is dominated by winter spawners. Exploratory classification of historical fishery samples suggested a change over time with spring and winter spawners present in near equal proportion in the early 1990s and winter spawners dominating in the early 1980s. Otolith-based stock composition analysis has the potential to support monitoring and assessment of cod populations in the Gulf of Maine.

Fisheries and biological characteristics and state of stocks of the main commercial fish species in Beloye Lake

The current composition of the ichthyofauna and the importance for fisheries of the main fish species in Beloye Lake (Vologda Region) is described in the article based on research materials from 2018 – 2022. The biological features and commercial use of twelve most valuable fish species are summarized as result of the composition of industrial and research catches studies. The size and age composition of catches, the age of puberty, the timing and conditions of spawning, and the feeding patterns of fishes were studied. The influence of net fishing gear with different mesh spacing on commercial fish populations and the magnitude of nets fishing productivity (fishing effort) were studied for the first time. The role of the most important fish species for industrial fisheries in Beloye Lake was assessed.

Patterns of spawning and settlement of reef fishes as strategic responses to post-settlement competition

Settlement is a critical transition in the life history of reef fish, and the timing of this event can have a strong effect on fitness. Key factors that influence settlement timing are predictable lunar cyclic variation in tidal currents, moonlight, and nocturnal predation risk as larvae transition from pelagic to benthic environments. However, populations typically display wide variation in the arrival of settlers over the lunar cycle. This variation is often hypothesized to result from unpredictable conditions in the pelagic environment and bet-hedging by spawning adults. Here, we consider the hypothesis that the timing of spawning and settlement is a strategic response to post-settlement competition. We use a game theoretic model to predict spawning and settlement distributions when fish face a tradeoff between minimizing density-independent predation risk while crossing the reef crest vs. avoiding high competitor density on settlement habitat. In general, we expect competition to spread spawning over time such that settlement is distributed around the lunar phase with the lowest predation risk, similar to an ideal free distribution in which competition spreads competitors across space. We examine the effects of overcompensating density dependence, age-dependent competition, and competition among daily settler cohorts. Our model predicts that even in the absence of stochastic variation in the larval environment, competition can result in qualitative divergence between spawning and settlement distributions. Furthermore, we show that if competitive strength increases with settler age, competition results in covariation between settler age and settlement date, with older larvae settling when predation risk is minimal. We predict that competition between daily cohorts delays peak settlement, with priority effects potentially selecting for a multimodal settlement distribution.

The reproductive costs of bitterling fish and zebra mussel parasitism to a unionid mussel

Unionid mussels are one of the most vulnerable groups of animals, with multitude of factors responsible for the decline of their populations in the freshwater ecosystems. Many of those causes stem from interspecific relationships. Direct data on the reproductive costs incurred to unionids through parasitism by fish and other mussel species are incomplete. We used field experiments to test whether reproduction of the swollen river mussel (Unio tumidus) is affected by parasitism by the European bitterling fish (Rhodeus amarus) and zebra mussel (Dreissena polymorpha). We documented that bitterling brood can develop in the gills of female, male and hermaphrodite mussels. Our research showed that male mussels carried more fish offspring than female U. tumidus and bitterling embryo survival appeared higher in the outer gill demibranchs. Parasitised female U. tumidus suffered reduced fecundity in terms of a reduced number of mature ovulated oocytes and increased oocyte degeneration. Our data lend clear support to the hypothesis that bitterling fish embryos parasitizing mussel gills and epibiont zebra mussel fouling unionid shells represent a major cost to the reproductive success of their host mussels. Extended gonadal activity (multiple spawning) of U. tumidus spreads their spawning time over a longer period, which may mitigate the costs of parasitism.

The effect of surveillance fishing on migration distance of Atlantic Salmon during the spawning period

AbstractObjectiveSurveillance fishing surveys can be performed to estimate the proportion of farmed salmon represented in the spawning stock of native Atlantic Salmon Salmo salar populations. These surveys take place after the recreational fishing period and therefore closer to the spawning period than the open recreational fishing season. Although catch‐and‐release angling has been demonstrated to affect salmon migration during the summer months, surveillance fishing that is conducted close to the spawning time could have more severe effects.MethodsTo test this, the migration distance of Atlantic Salmon (n = 74) caught in the Orkla River, Norway, was tracked by use of radiotelemetry. One group was tagged during the regular fishing season in the summer (control group), whereas another group was tagged in autumn during surveillance fishing (surveillance group).ResultSixty‐one salmon remained for analysis after we excluded fish that were recaptured, died, or migrated to other rivers. Relocation of the salmon during autumn (October 11–31) was used to compare movements and test for differences in migration using negative binomial regression because distances were nonnegative integers. During the tracking period, the surveillance group moved 12 ± 14 km (mean ± standard deviation) and the control group moved 13 ± 15 km; both groups moved 1 ± 2 km/day on average. There was no evidence that surveillance fishing impacted movement of the salmon compared to controls. However, one salmon died after tagging and three were not released due to injuries; total mortality of 9% during surveillance fishing could be unsustainable for smaller populations. Consequently, factors such as surveillance sample size, the status of the salmon population, and the population size should be assessed for each river individually when deciding the necessity of and approach to surveillance fishing.ConclusionThe results support existing recommendations to use careful handling and to end surveillance at least 2 weeks prior to the expected onset of spawning, thus providing a sufficiently long period for recovery after surveillance fishing.

Some biological aspects of chacunda gizzard shad, Anodontostoma chacunda (Hamilton, 1822) from the Bay of Bengal, Bangladesh

Anodontostoma chacunda is a commercial fish species in the market and is usually consumed in fresh, smoked, and dried forms. This study investigated the population structure, length-weight relationships (LWR), condition factor (KF), size at sexual maturity (Lm), and breeding season of A. chacunda in the Bay of Bengal, Bangladesh, using the data collected from January to December 2020. A total of 1061 individuals were collected in the sampling period with the help of fishers. Total length (TL) and body weight (BW) were measured using a measuring board and an electronic balance. The TL ranged from 12.50 to 26.70 cm. The allometric coefficient (b) value was 3.34, indicating positive allometric growth in this species. The fish is in good condition, evidenced by its condition factor (KF) ranging between 0.88 and 1.73. Maturity size ranged from 15.40 to 16.80 cm (TL) based on three distinguished models. Spawning time lasts from January to May and from September to December. The peak spawning time was December of A. chacunda in the Bay of Bengal. This information could prove valuable for fisheries researchers and biologists, facilitating efforts toward the conservation and sustainable management of this species.

Forecasted changes to the timing of Pacific herring Clupea pallasii spawn in a warming ocean

Pacific herring Clupea pallasii are a critical commercial and subsistence fish species and play a keystone role in the ecology and culture of the North Pacific. The annual herring spawn, in which mature herring migrate nearshore to deposit eggs along the coastline, is an important event linked to the migration of seabirds and marine mammals as well as a subsistence harvest for Alaska Natives and First Nations in British Columbia. Previous work has suggested that environmental variables and broad teleconnection indices play a role in the magnitude and phenology of spawning; however, the effects of these drivers have not been examined in the context of future climate scenarios. Here, we modeled variability in the timing of herring spawn across British Columbia and Southeast Alaska using survey data from 1951-2022. We created a model using Pacific teleconnection indices, sea surface temperature (SST), tidal height, and lagged data to predict spawn date anomalies (SDAs) across 9 spawning regions. SDAs were significantly affected by the Oceanic Niño Index, Pacific Decadal Oscillation, SST, and lagged SDAs. We then used this model to predict SDAs using projected SST from climate models and bootstrapped teleconnection data from 2025-2100. Future herring spawn timing trends earlier on average with warming SSTs, although the magnitude is relatively small, occurring 9 d earlier on average by 2100. This changing phenology, though small, varied by region and may have ecosystem-level ramifications and create timing mismatch for migratory species. However, our findings also reinforce the importance of other physical factors not measured in this study, such as photoperiod, which drive herring spawn timing.

Coral spawning patterns on the Luhuitou fringing reef in Hainan Island of the northern South China Sea

Observation of coral spawning times is valuable to detect spawning patterns and identify the potential mechanisms behind coral reproduction. Although large amount of data on global coral spawning records have become available over the past decades, information on coral spawning in the northern South China Sea remains scarce. In this study, we investigated the spawning patterns of scleractinian corals in Luhuitou fringing reef, Hainan Island, China, from 2009 to 2021 in relation to lunar cycles (month and day). The spawning times of 22 coral species from five genera (Acropora, Montipora, Platygyra, Dipsastraea, and Galaxea) within three families (Acroporidae, Merulinidae, and Euphylliidae) were recorded, with spawning occurring from lunar February to May 2009–2021. Recorded spawning events started at a period of increasing seawater temperature. Acropora, the most documented genus, spawned between lunar February and April, but primarily in lunar March. Importantly, the spawning time of Acropora was delayed for one lunar month in 2016 most likely due to a rapid decrease in monthly mean seawater temperature in lunar February. Spawning lunar days before, on or after full moon of corals in the Luhuitou Reef, including those of the Acropora species, were highly variable between years even for the same species. No predictable pattern of spawning times can thus be detected. Nonetheless, our results fill up an information gap on coral spawning patterns in the northern South China Sea that may be useful for further understanding of the reproductive biology of scleractinian corals throughout the Indo–West Pacific.

Distribution and abundance of ichthyoplankton in natural al artificial reefs in Edremit Bay, Northern Aegean Sea, Türkiye

Edremit Bay is one of the important areas for small–scale fishing in the North Aegean Sea. For this reason, more detailed ichthyoplankton studies should be continued to evaluate the fish stock status of the region, calculate the adult fish biomass, and determine the spawning period, place, and time of fish species. In addition, from 2011 to 2013, artificial reefs were constructed in Edremit Bay. Regular investigation of fish eggs and larvae in the region influenced by the Edremit Bay artificial reef would provide better knowledge of the structure and function of the local ecosystem and provide a basis for monitoring the marine ecosystem in the area. The current research examined the species abundance and distribution of surface plankton samples collected in 2015 and 2016. The evaluation also included the influence of abiotic environmental factors such as temperature, pH, chlorophyll a (chl–a), salinity, depth, and dissolved oxygen. Throughout the research, 3345 eggs and 176 larvae were analyzed. 57 species of eggs and larvae were identified. Eggs were not found in the natural reef (S3) in the summer and winter of 2015, while the highest egg abundance (212.83·100 m-3) was recorded in the natural reef (S1) in the summer of 2016. Larvae were not found in the natural reefs (S2 and S3) in the summer, autumn and winter of 2015 and in the artificial reefs (S4 and S5) in the summer and autumn in 2015 while the highest larvae abundance (8.12·100 m-3) on the artificial reef (S1) in summer 2016. Although the natural reefs had the highest number of species (30 species), the artificial reefs showed the lowest species diversity (17 species).

Recruitment of European sea bass (Dicentrarchus labrax) in northerly UK estuaries indicates a mismatch between spawning and fisheries closure periods.

European sea bass (Dicentrarchus labrax) is a species of high commercial and recreational value, but it exhibits highly variable recruitment rates and has been subject to recent declines. Emergency management measures put in place to protect spawning stocks include the annual closure of commercial and recreational fisheries over a 2-month, February-March, window. Whether this protection measure is having the desired outcome for this data-poor species remains unclear. Otolith microstructural analyses (counts and widths of daily growth rings and check marks indicative of settlement) were used to estimate (1) spawn timing, (2) pelagic larval duration and settlement timing, (3) growth rate and condition, and (4) the otolith-fish size relationship for juvenile European sea bass caught from two estuaries in Wales (Dwyryd, Y Foryd), located at the northern edge of the species range. We observed a significant mismatch between the timing of fisheries closures and the spawning, with 99.2% of recruits having been spawned after the fishery had reopened (back-calculated median spawn date = May 5 ± 17 days SD), suggesting that the closure may be too early to adequately protect this population. Further, we present the first empirically derived estimates of pelagic larval duration for sea bass recruits settling in UK habitats, which showed a strong negative relationship with spawn date. Finally, we found significant differences in fish condition between the two estuaries, suggesting local variation in habitat quality. The results suggest that the timing of current fisheries closures may not be adequately protecting the spawners supplying these northernmost estuaries, which are likely to become increasingly important as sea bass distributions shift northward in our climate future.

Climate‐influenced phenology of larval fish transport in a large lake

AbstractElucidating physical transport phenologies in large lakes can aid understanding of larval recruitment dynamics. Here, we integrate a series of climate, hydrodynamic, biogeochemical, and Lagrangian particle dispersion models to: (1) simulate hatch and transport of fish larvae throughout an illustrative large lake, (2) evaluate patterns of historic and potential future climate‐induced larval transport, and (3) consider consequences for overlap with suitable temperatures and prey. Simulations demonstrate that relative offshore transport increases seasonally, with shifts toward offshore transport occurring earlier during relatively warm historic and future simulations. Intra‐ and inter‐annual trends in transport were robust to assumed pelagic larval duration and precise location and timing of hatching. Larvae retained nearshore generally encountered more favorable temperatures and zooplankton densities compared to larvae transported offshore. Larval exploitation of nearshore resources under climate change may depend on a concomitant shift to earlier spawning and hatch times in advance of earlier offshore transport.

Southeast Florida large Orbicella faveolata are highly fecund without evident disease intervention effects

The recent widespread mortality and tissue loss in Florida from stony coral tissue loss disease (SCTLD) has propelled the need for assisted reproduction to restore reefs, especially for the ESA listed species Orbicella faveolata. In situ gamete collection can be challenging due to the weather and resources (boats and divers) required during the expected spawning window. In the northern portion of the Florida coral reef tract, coral spawn collection has been even more difficult due to historical inconsistency in annual spawning times and the potential for “zombie” corals, i.e. large but reproductively senescent individuals. Therefore, we examined the current reproductive potential of seven large (>2 m diameter) O. faveolata colonies from this region, quantified their fecundity, and estimated the spawning timeframe using histology. Additionally, we explored whether previous SCTLD lesion amoxycillin treatments affected reproductive metrics. Understanding the reproductive capacity and spawning timing of these large corals, given their history of disease and disease treatment, is critical to evaluate potential impacts of SCTLD treatments and the success of assisted reproduction efforts. The histological analysis coupled with in-water observations indicated a probable split-spawn in these individuals in 2020, although the dates of spawning may not be consistent with predictions for the wider Caribbean or with other colonies in Miami and the Florida Keys. All seven large O. faveolata colonies were found to contain abundant oocytes, with no obvious impact of SCTLD treatments on gamete development or fecundity.

Projecting marine fish distributions during early life stages under future climate scenarios

AbstractChanges to Earth's climate affect organisms globally; in marine systems, these impacts are seen through warming water temperatures, ocean acidification, hypoxia and frequent marine heatwaves. These effects may lead to the movement of species to more favourable conditions. While climate‐driven movement is well studied at the adult stage, how the early life stages of marine fish will respond to future variability is less clear. Many fish species are constrained by specific spawning locations or phenology. Spawning in certain locations allows for local retention of offspring, while precise timing can facilitate transport of offspring to nursery locations through seasonal circulation patterns. Our research investigates how changing oceans impact the location and timing of spawning of Bering Sea groundfishes over the next century. We used ROMS SST and SSS model output and NOAA survey data in species distribution models to hindcast and project distributions and centre of gravity for eggs and larvae of six groundfish species. Our analyses found that most of our study species exhibit flexible geography. However, the speed and direction of egg and larval movement did not track the speed and direction of their respective thermal niches. Hence, the projected distributional patterns of adult stages may be limited by their early life stages. This response is likely to be mirrored globally by other species with planktonic eggs and larvae. These results indicate that life history considerations are critical for the management of commercially important species, as effects on early life stages are strongly connected to the success or failure of adult populations.

Spawning fish maintains trophic synchrony across time and space beyond thermal drivers.

Increasing ocean temperature will speed up physiological rates of ectotherms. In fish, this is suggested to cause earlier spawning due to faster oocyte growth rates. Over time, this could cause spawning time to become decoupled from the timing of offspring food resources, a phenomenon referred to as trophic asynchrony. We used biological data, including body length, age, and gonad developmental stages collected from >125,000 individual Northeast Arctic cod (Gadus morhua) sampled between 59 and 73° N in 1980-2019. Combined with experimental data on oocyte growth rates, our analyses show that cod spawned progressively earlier by about a week per decade, partly due to ocean warming. It also appears that spawning time varied by more than 40 days, depending on year and spawning location. The significant plasticity in spawning time seems to be fine-tuned to the local phytoplankton spring bloom phenology. This ability to partly overcome thermal drivers and thus modulate spawning time could allow individuals to maximize fitness by closely tracking local environmental conditions important for offspring survival. Our finding highlights a new dimension for trophic match-mismatch and should be an important consideration in models used to predict phenology dynamics in a warmer climate.

Land use change and coastal water darkening drive synchronous dynamics in phytoplankton and fish phenology on centennial timescales

AbstractAt high latitudes, the suitable window for timing reproductive events is particularly narrow, promoting tight synchrony between trophic levels. Climate change may disrupt this synchrony due to diverging responses to temperature between, for example, the early life stages of higher trophic levels and their food resources. Evidence for this is equivocal, and the role of compensatory mechanisms is poorly understood. Here, we show how a combination of ocean warming and coastal water darkening drive long‐term changes in phytoplankton spring bloom timing in Lofoten Norway, and how spawning time of Northeast Arctic cod responds in synchrony. Spring bloom timing was derived from hydrographical observations dating back to 1936, while cod spawning time was estimated from weekly fisheries catch and roe landing data since 1877. Our results suggest that land use change and freshwater run‐off causing coastal water darkening has gradually delayed the spring bloom up to the late 1980s after which ocean warming has caused it to advance. The cod appear to track phytoplankton dynamics by timing gonadal development and spawning to maximize overlap between offspring hatch date and predicted resource availability. This finding emphasises the importance of land–ocean coupling for coastal ecosystem functioning, and the potential for fish to adapt through phenotypic plasticity.

Long-term aquarium records delineate the synchronized spawning strategy of Acropora corals.

Aligning spawning timing with seasonal environmental changes is critical for both terrestrial and aquatic organisms. However, mechanisms to regulate reproductive activity in response to environmental factors are not well understood, partly owing to the technical difficulty in maintaining detailed long-term observational data of the reproductive activities in the same population across years. In this study, we present an application of the aquarium system to examine the long-term spawning properties of corals. Spawning records over a 15-year period at the Okinawa Churaumi Aquarium revealed that the spawning timing of Acropora corals in aquarium tanks aligned well with that of wild corals from a neighbouring reef. Using the aquarium population as a model, we investigated the relationship between key environmental factors and the timing of the first and peak spawning dates of Acropora corals during a 15-year period. The results suggest that the spawning window of each spawning season is largely influenced by the water temperature and that the timing of peak spawning can be fine-tuned in response to environmental fluctuations. This behavioural feature can prevent synchronous spawning events during unfavourable environmental conditions and increase long-term reproductive reliability.

Investigating the timing of spawning of two sea urchins (Tripneustes gratilla and Toxopneustes pileolus)

AbstractMany marine organisms broadcast gametes for external fertilization, thus conspecifics need to concentrate the time of gamete release through synchronization with environmental factors. We investigated the timing of spawning in two sea urchin species, Tripneustes gratilla and Toxopneustes pileolus, by assessing the spawning potential of individuals using both surveys and experiments in southern Taiwan from March to November 2010. We developed a new method to observe the spawning potential without sacrificing any individuals, defining those individuals‐initiated spawning within 30 min after 10 s of exposure to air as having the spawning potential. We discovered that the percentage of individuals with spawning potential, that is, the spawning ratios of the population, varied greatly from 0% to 80% in To. pileolus and from 0% to 50% in Tr. gratilla within the reproductive seasons. We evaluated the possibility of a lunar/semilunar rhythm of spawning ratios of the population and tested three environmental factors, that is, light intensity, tide, and temperature that could potentially affect the spawning potential of the sea urchins by experiments. Individuals with spawning potential were neither randomly nor evenly distributed among days but were aggregated on certain days; however, no lunar/semilunar rhythm of the spawning ratios was detected within the reproductive season. The possible role of the tidal factor within a day was not found in experiments in either species. However, when water temperature was >27°C in our surveys, significantly higher spawning ratios were observed in To. pileolus, but not in Tr. gratilla in the reproductive season. A further temperature experiment in To. pileolus supported the positive role of high temperature on the spawning ratios of individuals. In addition, To. pileolus was more likely to spawn during the day than at night, and the light/dark experiments suggested that the spawning potential was controlled by an endogenous biological clock rather than by the ambient light conditions directly. The lack of rhythmic pattern and yet concentrated spawning of these sea urchins may be adaptive to avoid predation.

Effect of a long photoperiod on the timing of spawning in the Pacific bluefin tuna, Thunnus orientalis

In this study, we examined the effects of a long photoperiod on the reproduction of Pacific bluefin tuna (Thunnus orientalis) in a land-based tank. Three-year-old fish were shifted from a short (10.5 L:13.5D) to long (15 L:9D) photoperiod in December. The broodstocks exhibited gonadal development after this photoperiod change and spawned spontaneously the following March, approximately three months earlier than the normal spawning season. Although the results were based on data from a small sample size of fish, the study suggests that a long photoperiod induces the onset of gonadal development in Pacific bluefin tuna, thereby accelerating their spawning time.