Natural Spawning Research Articles

Restored river habitat provides a natural spawning area for a critically endangered landlocked Atlantic salmon population.

Supplementing endangered fish populations with captive bred individuals is a common practice in conservation management. The aim of supplementary releases from hatchery broodstocks is to maintain the viability of populations by maintaining their genetic diversity. Landlocked Lake Saimaa salmon (Salmo salar m. sebago) has been critically endangered for the past half-century. As a result of anthropogenic disturbance, especially construction of hydroelectric power plants, the Lake Saimaa salmon has become completely dependent on hatchery broodstock. Recently, habitat restoration has been done in one of the former spawning rivers with the aim of creating a new natural spawning ground for the critically endangered population. Hatchery fish releases have also been revised so that in addition to juveniles, adult fish from the hatchery and from the wild have been released into the restored river. We assessed here if a restored river stretch can be used as a natural spawning ground and juvenile production area with the aim of improving genetic diversity of the critically endangered Lake Saimaa salmon. By constructing a pedigree of the released adults, and juveniles sampled from the restored river, we found that the majority of the released adults had produced offspring in the river. We also found that wild-caught spawners that were released into the restored river had much higher reproductive success than hatchery-reared parents that were released into the restored river at the same time. We found no significant differences in genetic diversity between the parent and offspring generations. Meanwhile, relatedness among different groups of adults and juveniles varied a lot. For example, while the hatchery-reared females were on average half-siblings, wild-caught females showed no significant relatedness. This highlights the importance of using pedigree information in planning the conservation and management of endangered populations, especially when artificial propagation is involved.

Lethal effect of filamentous algal blooms on Atlantic herring (Clupea harengus) eggs in the Baltic Sea

Abstract During this study, the effects of epiphytic filamentous algae on the survival of demersal spawned fish eggs were investigated in one of the most important spawning grounds of herring in the western Baltic Sea, which is subject to intense and ongoing eutrophication. In coastal marine ecosystems all over the world, eutrophication is a primary water quality issue, often resulting in mass developments of bloom‐forming algae. Macro‐algal blooms have immense ecological effects, as they alter the structure and the function of an ecosystem. Numerous fish species are affected, as they depend on those coastal areas for spawning and as juvenile habitats. A comparison of the survival of herring eggs on two natural spawning beds re‐vealed an immense impact of a filamentous algal bloom. The mortality rate reached nearly 100% in the area with massive occurrence of filamentous brown algae. Hypothesizing that the presence of filamentous algae facilitates herring egg mortality, field and laboratory experiments were conducted and revealed particular effects of distinct algal species. The survival rate of artificially spawned eggs on algal substrates and control substrates was compared. Whereas filamentous forms of the green alga Ulva intestinalis induced no immediate effect, significantly higher egg mortality was documented in experiments with the filamentous brown alga Pylaiella littoralis. Considering the ecological and economical importance of herring and other coastal spawners on the one hand and the persisting and increasing effects of eutrophication and climate change on the other hand, the results of our study clearly underpin the necessity to increase global efforts to reduce nutrient loads in coastal waters.

Out-of-season spawning affects the nutritional status and gene expression in both Atlantic salmon female broodstock and their offspring

The Atlantic salmon aquaculture industry relies on adjustments of female broodstock spawning season to meet the demand for delivery of embryos outside the natural spawning season. Earlier results from zebrafish have shown that parental micronutrient status program offspring metabolism. Therefore, the main hypothesis of this study was to investigate if out-of-season (off-season) broodstock (spawning in June, in land-based recirculation systems) and their offspring deviate in micronutrient status when compared to broodstock and offspring from normal spawning season. Both seasons of female Atlantic salmon broodstock were fed the same diet and starved for approximately the same time interval prior to spawning. We compared nutrients related to the 1C metabolism (vitamin B12, folate, vitamin B6, methionine), free amino acids (FAAs) and lipid classes in broodstock muscle and liver tissues, and during offspring ontogeny. In general, the off-season broodstock showed higher levels of folate, vitamin B6 and selected FAAs in muscle tissue, and higher levels of folate and lipids (cholesterol and sphingomyelin) in liver tissue compared to normal-season. Furthermore, embryos from off-season had reduced amounts of all the measured lipid classes, like cholesterol and sphingomyelin, and lower levels of one type of folate and changes in FAAs and N-metabolites. We discovered significant differences between the seasons in mRNA levels of genes controlling fatty acid synthesis and 1C metabolism in both broodstock liver and offspring. Moreover, for genes controlling the methylation of DNA; both maintenance and de novo DNA methyltransferases (DNMTs) were expressed at higher levels in off-season compared to normal-season offspring. Our results show, in general that normal spawning season broodstock allocated more nutrients to eggs than off-season. Our results indicate a potential for improved maturation for off-season group to obtain a higher offspring growth potential, and this argues for a reassessment of the nutritional influence from broodstock to offspring and the consequences through nutritional programming.

Does construction in the spawning ground improve the riverbed conditions making it suitable for spawning of the Ryukyu-ayu Plecoglossus altivelis ryukyuensis?

Maintaining a certain number of spawning grounds for endangered fish is particularly important in rivers and streams where the environment changes drastically through floods and exploitations. Ryukyu-ayu Plecoglossus altivelis ryukyuensis is an endangered annual fish inhabiting the few streams and rivers flowing through the Amami-Oshima Island, southern Japan, and spawns in the lower reaches at sites with the specific riverbed conditions. In the island, resident volunteers along with researchers modify riverbed manually to provide conditions suitable for the natural spawning of the fish every year. This study investigated the effects of these activities on the riverbed conditions and consequently on the spawning by Ryukyu-ayu in two rivers. Our results showed that riverbed hardness and the amount of silt significantly decreased in the modified areas, but not in the adjacent unmodified areas. In one of the two rivers, the modification suppressed the settlement of net-spinning caddisfly larvae Stenopsyche schmidi that promote consolidation of the riverbed. The riverbed conditions in the modified areas were similar to those in the sites where P. a. ryukyuensis indeed spawned. These results suggest that manual modification is efficient in improving riverbed conditions for the spawning of Ryukyu-ayu. However, the eggs of the fish were not found at the modified areas in both rivers. It will be necessary to develop effective and practical ways of selecting sites for modification without obstructing the natural spawning in this fish.

ESTIMATION OF ABUNDANCE FOR THE MIGRATING JUVENILE PINK SALMON IN THE RIVERS OF SAKHALIN AND ITURUP ISLANDS IN 2019

Number of the pink salmon fry migrating downstream from their spawning grounds in the control rivers in 2019 is assessed as 17546.2 . 103and 14795.7 . 103ind. for the Dagi and Bolshoi Khuzi Rivers (northeastern Sakhalin), as 89.1 . 103and 2636.1 . 103ind. for the Poronai River tributaries — the Kholodny and Orlovka, as 2759.8 . 103and 21456.0 . 103ind. for the Lazovaya and Pugachevka Rivers (western coast of the Patience/Terpeniya Bay), as 5803.8 . 103 and 19020.0 . 103ind. for the Voznesenka and Ochepuha Rivers (southeastern Sakhalin), as 1822.4 . 103and 2139.0 . 103for the Taranai and Kura Rivers (Aniva Bay coast), and as 15834.1 . 103and 7626.1 . 103ind. for the Rybatskaya and Olya Rivers (Iturup Island), respectively. In all areas, the pink juveniles migrated from the spawning grounds earlier than usual, obviously because of accelerated development of the embryos in conditions of abnormally warm autumn. The number of juveniles migrated from all spawning grounds in the rivers of respective regions is estimated taking into account the escapement of pink salmon spawners and the downstream migration index determined for the control rivers (ratio of the spawners escapement and the number of subsequent downstream migrating juveniles): the total number for the natural spawning grounds is estimated as 1168.9 . 106ind. for the rivers of the eastern coast of Sakhalin (including the Aniva Bay) and 471.1 . 106ind. for the rivers of Iturup Island (Okhotsk Sea coast). Additional 141.3 . 106ind. were released from artificial hatcheries of eastern Sakhalin and 122.0 . 106ind. — from artificial hatcheries of Iturup Island. The downstream migration is considered as highly abundant for northeastern Sakhalin and Iturup Island, but is insufficiently abundant for the Patience/Terpeniya Bay and Aniva Bay where the landings of this generation should be limited. The pink salmon return to southeastern Sakhalin in 2020 is expected to be better than in 2018 due to satisfactory abundance of the juveniles from natural spawning grounds.

Catchment-scale effects of river fragmentation: A case study on restoring connectivity

More than two thirds of large rivers worldwide are fragmented, threatening freshwater biodiversity, river integrity, and the services that freshwater ecosystems provide for human populations around the globe. In an effort to alleviate the impacts of barriers, engineered solutions have been developed, though with somewhat underwhelming results. River restoration, especially dam removal, is viewed as the optimal option though seldom the go-to approach. In this study, we evaluated the effects of a large restoration project (pseudo dam removal) in River Kolding, Southern Jutland, Denmark, via a before-after-control-impact (BACI) approach. Using a large dataset of electrofishing data from 74 sites (including downstream unaffected sites, reconnected sites and upstream regulated sites), we found that habitat connectivity was restored successfully, with a large increase in young-of-the-year brown trout (Salmo trutta) at reconnected sites, reaching similar densities to downstream (non-affected) sites. We further observed a decrease in length at reconnected sites, suggesting that natural spawning and rearing habitats were successfully restored too.

Channel catfish ovarian fluid differentially enhances blue catfish sperm performance

For externally fertilizing fishes, interactions between male and female gametes have been shown to have remarkable impacts on sperm performance. Ovarian fluid (OF) and its ability to alter the swimming behavior of fish sperm makes it a determining factor of fertility. With the expansion of channel catfish (Ictalurus punctatus) ♀ × blue catfish (Ictalurus furcatus) ♂ hybrid aquaculture, it is essential to understand the impacts during fertilization and the magnitude such gametic interactions have on sperm performance and subsequent male fertility potential. This study was conducted to address the following: 1) activate blue catfish sperm with/without channel catfish OF to determine impacts on sperm performance and 2) assess if sperm behave differently when activated in the OF from individual females. Sperm (n = 4 males) were activated without OF (control) and with diluted OF from unique females (n = 6), creating 24 experimental crosses. Sperm motility (%), velocity (VCL), and longevity were analyzed using computer assisted sperm analyses software. With OF incorporated in the activation media, sperm velocity was significantly higher than the control at 10, 20, and 30 s post-activation. OF did not have an impact on motility for any females at 10 s and 20 s post-activation but became significantly higher than the control at 30 s. In all cases, OF treatments greatly increased longevity. Male × female interactions were highly significant, such that motility, velocity, and longevity were dependent on specific male-female pairs. This information shows that OF should be incorporated in aquatic media to simulate natural spawning conditions and accurately assess the fluid mechanics of sperm propulsion for each male. Additionally, there are mechanisms that drive gamete interactions that need to be explored further, which may improve selection of male-female pairs for in-vitro fertilization. On a broad scale, our results also help to shed light on the complexities of fertilization and fish reproduction overall, which may have implications for recruitment variability and recovery strategies of threatened and/or endangered freshwater species.

Reproductive performance of captive Senegalese sole, Solea senegalensis, according to the origin (wild or cultured) and gender

Aim of study: The reproductive performance over a five year period in three different sole broodstocks: wild males with cultured females (WM), cultured males with wild females (CM), and a control of cultured males and females (C).Area of study: Cantabria, Northern Spain.Material and methods: The parental contribution was evaluated through the allocation of hatched larvae and a behavioural study was performed using underwater video recordings.Main results: Fertilized natural spawns were only obtained from group WM showing a significantly higher mean annual volume of floating eggs compared with groups CM and C. Over the entire 5-yr a higher number of spawns, total and floating volumes of eggs were obtained compared with groups CM and C. The analysis of four polymorphic microsatellites enabled the identification of the individuals involved in the fertile spawns by parental assignment. The percentage of individuals contributing to spawns ranged between 56.3% and 75% showing fidelity patterns. However between 46.2% and 68.6% of the contribution to production was a result of the crossing of three single couples. According to the behaviour analysis, group WM presented the highest peak of activity at 20:00 h and a higher activity profile during the night, moreover, the courtship behaviours “swim follow” and “swim followed”, were only recorded in group WM.Research highlights: The study has importance for aquaculture as it demonstrated how broodstocks with wild males and cultured females had adequate egg production for a commercial operation to supply eggs and implement single sex breeding programs.

Understanding the Relative Roles of Salmon Spawner Enrichment and Disturbance: A High-Frequency, Multi-Habitat Field and Modeling Approach

Organisms exert multiple, often-contrasting, influences on ecosystems. Migrating Pacific salmon (Oncorhynchus spp.) deliver nutrients to freshwater ecosystems, but also disturb benthic sediments during upstream migration and nest building. The relative importance of these contrasting roles is not well understood, especially not in relation to the temporal dynamics of other environmental drivers. To assess the influence of salmon-mediated enrichment and disturbance, we measured stream biofilm metrics (production, respiration, chlorophyll a [chla], ash-free dry mass, stable isotope signatures) and environmental variables (spawner and carcass abundance, dissolved nutrients, temperature, discharge, light) from July through September in multiple habitats of a southeast Alaska stream. Biofilm production and biomass increased before and early in the salmon run, but declined later in the run. Biofilm stable isotope composition indicated incorporation of salmon-derived carbon and nitrogen (N) during the latter part of the run. Biofilm biomass differed among benthic habitat types (i.e., riffles, pools stream edges) but temporal patterns were generally similar, suggesting salmon and environmental influences were not habitat-specific. We used this high-frequency field data to parameterize an ordinary differential equation model for dissolved inorganic N, chla, and cellular N, and estimated model parameters using Marcov Chain Monte Carlo. Posterior distributions indicated that 1) habitats and locations were generally similar in model parameters, 2) removing the effect of salmon resulted in no change in biofilm chla early in the run (mid-August), but did show a decrease for some habitats later in the run (September), and 3) the overall integrated salmon effect over the run was one of biofilm loss. Only the combination of high frequency biofilm and environmental data collections with a process-based model, allowed us to determine how environmental context dynamics interact with salmon run dynamics to modulate the biofilm response in natal spawning streams. High-frequency field data combined with modeling provides a critical tool to gain a mechanistic understanding of resource subsidies, especially those from organisms that have other influences and roles, in relation to the environmental context and will allow us to evaluate the small and large scale importance of subsidies.

Growth performance and survival rate of Boeseman’s rainbowfish (Melanotaenia boesemani) in natural spawning technique at Depok, West Java, Indonesia

Boeseman’s rainbowfish is an endemic ornamental fish from Papua. This fish is popular because of its beauty and uniqueness. Problems that occur in rainbow fish farming are low growth rates and high mortality rates in the larvae stage. The purpose of this research is to analyze the growth performance and survival rate of Boeseman’s rainbowfish. This research was conducted at BRBIH Depok, West Java, on December 17, 2018, until January 17, 2019. The technique is used was natural spawning technique. In this technique used aquarium containers and fiberglass tanks. Maintenance of the parent is done by feeding Chironomus sp. twice a day. The parent selection is carried out before the spawning process. The results of spawning for 20 days had a fertilization rate of 91.47 % and a hatching rate of 86.12%. Growth monitoring results of the average growth rate were 0.0031 g/day, the specific growth rate was 0.013 – 0.095 %bb/day and the survival rate of larvae was 47.24%.

Influence of photoperiod and temperature manipulation on gonadal development and spawning in Caspian roach ( Rutilus rutilus caspicus ): Implications for artificial propagation

Caspian roach (Rutilus rutilus caspicus), a spring spawning teleost, were subjected to various photoperiod and temperature regimes to study the feasibility of shifting the timing of spawning for artificial propagation purposes. A total of 650 female reproductively mature R. rutilus caspicus were subjected to different photoperiod and temperature regimes including four light regimes (natural light (NL), 16 hr of light (L):8 hr of darkness (D), 9L:15D, 11L:13D), each affected by three temperature regimes (14, 20 and 24°C) for 70 days. Five fish per tank were randomly sampled on Feb. 10, Feb. 20, March 28, April 15 and April 30 (natural spawning time). Ovarian tissue sections were studied using light microscope and transmission electron microscope (TEM). The levels of 17‐β estradiol (E2) and 17α‐hydroxyprogesterone (OHP) were also measured in the serum samples. In late winter (March 28th), the gonadal maturation and spawning were accelerated in fish treated with the long day length (16L/8D) and warm temperature (20°C). While, the maturation of oocytes and spawning delayed in fish exposed to low temperature (14°C) and short day length (9L/15D and 11L/13D). Photoperiod seems to play a more important role in the ovarian development of the R. rutilus caspicus compared to temperature; since even among the fish treated with the lowest temperature (14°C), those exposed to a longer day length (16L/8D), matured and spawned earlier than the others. Considering that the earliest spawning occurred in R. rutilus caspicus treated with 16L/8D at 20°C and the latest spawning occurred in fish exposed to low temperature and short photoperiod, it can be concluded that temperature and photoperiod play an important role in accelerating oocyte maturation and spawning.

Fishery organization in the Lower Dniestr and in the Dnistrovsky liman (analytical overview)

According to official statistics, the long-term dynamics of catch of the main commercial fish species and invertebrates of the Lower Dniester, changes in the structure and variations in the volume of catches are shown. Fisheries in the lower Dniester basin are characterized by a very high level of exploitation of aquatic bioresources, which, along with other factors of anthropogenic impact, has led to changes in the structure of ichthyocenosis. The rapid increase in the number of prussian carp in the last five years indicates a significant imbalance of the ecosystem. Modern approaches to the organization and regulation of fisheries, including commercial, amateur, in the waters of the NRF are considered. The current regulatory documents governing the organization and regulation of fisheries are analyzed. The predominance of IUU fishing over the legal forms of fisheries activities was noted, which seriously threatens the state of commercial aquatic bioresources and makes their rational sustainable use impossible. The problem of reliability of statistical data on the catch volumes of aquatic biological resources is noted. Official fishery statistics provide not only significantly reduced catches but also a distorted catch structure. There are practically no reliable data on fishing by amateur fishermen. The low efficiency of measures taken for the artificial reproduction of aquatic biological resources is shown. The most promising route is the restoration of natural spawning areas downstream of the river and in the estuary, which can have a greater environmental and economic impact than artificial reproduction. Proposals to improve the protection and rational use of aquatic bioresources in the Dniester basin were considered.

Size at Maturation, Spawning Variability and Fecundity in the Queen Conch, Aliger gigas

The queen conch (Aliger gigas) resource is one of the most important in the Caribbean. While aspects of queen conch reproduction have been studied, e.g., size—at—maturity, spawning season, and density—based Allee effects, there is little information on other important aspects. From 210 lipped queen conch collected off southwest Puerto Rico, histological examination of gonads showed that 50% maturation occurred at 9 mm lip thickness. Experimental caged queen conch held on a natural spawning ground were monitored across the spawning season to evaluate fecundity and its variability across individuals and between nominal density treatments (2,000 vs 143 conch/ha). Near daily monitoring identified all egg masses to specific females, and all egg masses were retained to calculate the number of eggs. Conch in the low—density treatment produced more and larger egg masses over a longer spawning season than those in the high—density treatment. Within each density treatment, individual fecundity varied by a factor of 6. The maximum fecundity estimated was 22 million, the maximum number of egg masses spawned was 25, and the largest single egg mass contained 1.48 million eggs. Variability in fecundity was largely driven by length of the individual spawning season, but this may in turn have been dependent on the degree of maturation of females at the start of the spawning season. These results emphasize the importance of allowing queen conch to mature and further grow in lip thickness to ensure sufficient spawning to sustain reproductive capacity. This experimental approach could be used to assess variations in fecundity based on size (length, biomass) and age (lip thickness).

Intravital method for the obtaining genital products from the male african catfish

In industrial aquaculture, spawning of t*he Clarias catfish (lat. Clarias gariepinus) is complicated by the fact that it is impossible to obtain sperm due to the physiology of the fish. Fish farmers deal with the problem in different ways. They have to expect natural spawning, do a resection of the gonads or kill and dissect the fish (slaughter). We would like to propose a method for collecting sperm through the puncture of the gonads of the fish. The method is intended to save male broodstock. If the weight of the fish does not exceed 2 kg, the procedure can be performed any anesthesia. There is no need for the fish to be separated from the rest of the broodstock after the surgery. 43 of the 65 stimulated one-year-old males with an average weight of 1250 g have given motile sperm with a volume of 1.5 ± 0.1 ml.

Mini Review: Production and Economics Analysis Of Backyard Production of Tiger Grouper Epinephelus Fuscoguttatus Fingerlings in Situbondo, Indonesia

Application of backyard technology to produce tiger grouper fingerlings in the area of Situbondo is examined with emphasis on production system and economic structure. Complete hatcheries production system that employ full production systems from broodstock, maturation, spawning, larviculture and early nursery phase are common in this area. Natural spawning activities without the use of hormone or another chemical substance become the primary method to produce the larvae. Hatchery in Situbondo typically consist with concrete tank to culture the larva, sand filter and live food production tanks, including phytoplankton production system. While the nursery production system as an intermediate step between hatchery and grow-out production consist with concrete tank and grading system to reduce the size variation, cannibalism and to ensure there is no more than 30% difference in total length between the grade sizes within the culture tanks. The output of the economic analysis showed that with final survival rate about 10%, farmer in Situbondo still get a good annual return through the sales of fingerlings. From this situation, farmer still obtain high cash flow from backyard production system and about 69.06% rate of return to capital. Overall, backyard technology consists with hatchery and early nursery production system provide potential sources for poverty alleviation and support the sustainability of aquaculture production in Situbondo. Good economic structure and opportunity to participate in several government programs speed up the adoption of this technology and become an important chain for tiger grouper production system in Indonesia.

Redds of brown trout in the deep channels of a hydroelectric power station

AbstractNatural spawning redds of brown trout were surveyed for the first time in 1−6‐m deep urban channels of a hydroelectric power station (HEP) between two lakes in Finland, by scuba diving and wading. Before damming a century ago, thousands of lake migrating trout spawners ascended through the rapids to upstream spawning areas. Between 2015 and 2018, 11 trout redds were observed at depths of 250−340 cm; these may be the deepest reported in running waters. Nine redds were found at depths of 75−230 cm. The nearest redds were situated only 55 m upstream and 110 m downstream from the HEP inflow and outflow, respectively. Channel substrate and trout redds were dominated by particle size classes 32−64, 64−128, and 16−32 mm. The risk of diving in the area increased due to the high amount of litter on the riverbed. Observations of wild trout parr by local anglers provide evidence that natural spawning produces some fish in the HEP channels.

Biological Parameters of Blacksaddled Coralgrouper (Plectropomus laevis Lacepède, 1801) Eggs and Larvae

Blacksaddled coralgrouper, Plectropomus laevis, is an endangered species of marine fish. As part of conserving their existence in the wild, culture of this species has been started. However, knowledge of biological parameters of this species as important indicators to observe the fish growth in mariculture scale, is limited. The purpose of this study was to observe biological parameters during eggs, larval to juvenile stage of blacksaddled coralgrouper in mariculture hatchery. The eggs were obtained from natural spawning of domesticated broodstocks. Larvae rearing was done in hatchery at three different times as replicates. Larval were fed with zooplankton which consist of rotifers Brachionus sp., wild copepods and Artemia. Artificial feed was also given to the fish larvae. Larval samples were taken one Day After Hatching (DAH), then continued every 5 days started at 5 to 45 DAH by using five larvae each sampling time. The observed parameters were diameter of eggs and oil globule, total length and standard length of larvae length of dorsal and pelvic fin spines of larvae. Furthermore, growth pattern of those length parameters was analysed by regression equation. The result showed that diameter of blacksaddled coralgrouper eggs was 835.19±15.29 µm, while oil globule was 177.78±10.30 µm. The growth patterns of larval total length and standard length were exponential, while dorsal and pelvic fin spines were polynomial. The length of time from larvae to achieve juvenile stage was range between 45-50 days. All of these information can be used as references either in larvae rearing or for further study of the fish.

Environmentally relevant concentrations of the common anxiolytic pharmaceutical oxazepam do not have acute effect on spawning behavior in mature male Atlantic salmon (Salmo salar) parr

Low concentrations of psychiatric drugs are commonly found in surface waters around the world, and their ability to alter behaviors in aquatic fauna has raised concerns about ecological effects. One critical effect that contamination can have in aquatic systems is modifications of reproductive behaviors. In this study, we hypothesized that oxazepam, a common anxiolytic drug and aquatic contaminant previously shown to induce anti-anxiety behavior in salmonids, also affects the reproductive behavior of Atlantic salmon (Salmo salar). To test this hypothesis, small sexually mature Atlantic salmon males (mature parr) were exposed to concentrations of oxazepam comparable to that of effluent water (1.9 µg/L). After 5 days of exposure, their reproductive behavior was compared with that of unexposed control individuals. Behavior was monitored in a large-scale flume aquarium that also contained a large male and a female to mimic natural spawning conditions for Atlantic salmon. Three behaviors were quantified for the mature parr; (a) amount of courting behavior towards female, (b) proximity to female, and (c) amount of attacks received from the large male. In contrast to our hypothesis, no difference in either courting behavior, proximity to female, or received aggression could be found between exposed and control male parr. Hence, our results indicate that there is no acute effect of the highest levels of oxazepam concentration reported for urban environments on spawning behavior of mature male parr, although chronic effects could not be ruled out.

Recent advances of marine ornamental fish larviculture: broodstock reproduction, live prey and feeding regimes, and comparison between demersal and pelagic spawners

AbstractMarine ornamental fish are a key component of the multimillion‐dollar marine aquarium trade industry, a controversial industry due to current heavy reliance on wild‐collected specimens. Aquaculture of marine ornamental fish is considered as a sustainable alternative, but it is still in the early stage of development. This review focuses on the current state of marine ornamental fish aquaculture, by covering topics on reef fish reproductive biology in captivity, traditional and novel live feeds, feeding regimes and visual environment in larviculture. Where possible, major differences between demersal and pelagic spawners are compared and discussed. Overall, for many ornamental fish species, natural spawning can be achieved in a captive environment without the use of hormone induction; however, sex identification and successful pairing for reef fish species could be a challenge. With the use of both traditional (rotifers and Artemia) and novel live feeds (e.g. marine copepods and ciliates), a range of breakthroughs in larval rearing of both demersal and pelagic spawning ornamental fish species have been achieved in recent years, although larval survival varies. To further improve the larval rearing success of marine ornamental fish, this review suggests that future research should focus on optimizing the use of live feed in terms of both quality and quantity, and establishment of well‐defined species‐specific larval feeding regime, as well as providing appropriate rearing condition through improved manipulation of light conditions and the ‘greenwater’ techniques in larval rearing.

Ocean acidification during prefertilization chemical communication affects sperm success.

Ocean acidification (OA) poses a major threat to marine organisms, particularly during reproduction when externally shed gametes are vulnerable to changes in seawater pH. Accordingly, several studies on OA have focused on how changes in seawater pH influence sperm behavior and/or rates of in vitro fertilization. By contrast, few studies have examined how pH influences prefertilization gamete interactions, which are crucial during natural spawning events in most externally fertilizing taxa. One mechanism of gamete interaction that forms an important component of fertilization in most taxa is communication between sperm and egg‐derived chemicals. These chemical signals, along with the physiological responses in sperm they elicit, are likely to be highly sensitive to changes in seawater chemistry. In this study, we experimentally tested this possibility using the blue mussel, Mytilus galloprovincialis, a species in which females have been shown to use egg‐derived chemicals to promote the success of sperm from genetically compatible males. We conducted trials in which sperm were allowed to swim in gradients of egg‐derived chemicals under different seawater CO2 (and therefore pH) treatments. We found that sperm had elevated fertilization rates after swimming in the presence of egg‐derived chemicals in low pH (pH 7.6) compared with ambient (pH 8.0) seawater. This observed effect could have important implications for the reproductive fitness of external fertilizers, where gamete compatibility plays a critical role in modulating reproduction in many species. For example, elevated sperm fertilization rates might disrupt the eggs' capacity to avoid fertilizations by genetically incompatible sperm. Our findings highlight the need to understand how OA affects the multiple stages of sperm‐egg interactions and to develop approaches that disentangle the implications of OA for female, male, and population fitness.