Male Spawning Research Articles

Effects of broodfish sex ratio, broodfish stocking density, and postspawn broodfish holding‐pond density on reproductive efficiency in pond‐spawned Channel Catfish

AbstractObjectiveThree trials were conducted to determine the effects of broodfish management on reproductive efficiency of pond‐spawned Channel Catfish Ictalurus punctatus.MethodsTrial 1 compared male to female broodfish sex ratios of 1:1 versus 1:4, trial 2 compared low (1065 kg/ha) versus high (2050 kg/ha) broodfish stocking densities, and trial 3 compared low (1525 kg/ha) and high (5780 kg/ha) postspawn broodfish holding‐pond densities on measures of reproductive efficiency.ResultMales had lower survival than females in all trials. Age, weight, and survival of broodfish were similar for each treatment within trials. A higher percentage of females spawned at the 1:1 male to female ratio than at the 1:4 ratio (40.8% versus 12.5%), resulting in more eggs per hectare, eggs per kilogram of broodfish, fry per hectare, and fry per kilogram of broodfish for the 1:1 ratio compared to the 1:4 ratio. Male spawning success (~31%) was similar for 1:1 and 1:4 sex ratios. Spawning fish weighed more than nonspawning fish for both sexes, and surviving males weighed less than nonsurviving males in trial 1. In trial 2, the percentage of egg masses collected per female stocked was higher for the high broodfish density than the low density (34.0% versus 16.4%), resulting in more eggs per hectare and fry per hectare for the high stocking density resulting in whole‐farm economic benefits ranging from US$323/ha to $828/ha primarily from the reduction in the area required for broodstock.ConclusionResults indicate that the 1:1 male to female broodfish ratio (trial 1) and high broodfish stocking density (trial 2) resulted in better reproduction than the 1:4 sex ratio and low broodfish stocking density. The effects of low versus high broodfish holding‐pond densities did not affect reproductive output.

Identification and Characterization of Hdh-FMRF2 Gene in Pacific Abalone and Its Possible Role in Reproduction and Larva Development.

FMRFamide-related peptides are neuropeptides involved in a wide range of biological processes, including reproduction and larval development. To characterize the involvement of FMRFamide in the reproduction and larval development of Pacific abalone Haliotis discus hannai, an FMRFamide cDNA (Hdh-FMRF2) was cloned from the cerebral ganglion (CG). Fluorescence in situ hybridization and qRT-PCR were performed for functional characterization. The Hdh-FMRF2 cDNA encoded 204 deduced amino acids that contained a putative signal peptide and four FaRP domains. The major population of Hdh-FMRF2 neuronal cell bodies was localized in the cortex of CG. Hdh-FMRF2 mRNA expression was significantly upregulated in CG during the mature stage of gonadal development and effective accumulative temperature (EAT) exposed abalone in both sexes. In the induced spawning event, Hdh-FMRF2 expression was significantly upregulated during spawning in males. However, no upregulation was observed in females, suggesting Hdh-FMRF2 might inhibit gamete release in female abalone. These results revealed Hdh-FMRF2 as a reproduction related peptide. Furthermore, mRNA expression in larval development suggested that this peptide was also involved in larval development during development of Pacific abalone. Collectively, this study provides evidence of possible involvement of an FMRFamide neuropeptide in the reproduction and larval development of Pacific abalone.

Reproductive cycles and spermatogenesis in male sterlet in industrial fish farming

With the advances made in the aquaculture industry, the role of males is becoming increasingly important, since their reproductive capacity determines the outcomes of artificial breeding. The key factor here is the developmental asynchrony of sex cells inherent in sturgeon males, which helps retain spawning readiness in males for longer periods of time without loss of quality of reproductive products produced by them. The paper presents the findings of the studies performed at the Konakovo Division of the Branch for Freshwater Fisheries of the Federal State Budget Scientific Institution “Russian Federal Research Institute of Fisheries and Oceanography” (VNIIPRKH), in a flow-through industrial farm and recirculating aquaculture system (RAS). These studies have confirmed the possibility to control spermatogenesis in sturgeons by changing the temperature during the prespawn period, thus improving the productivity of fish farms by prolonging the breeding season. The histological analysis of sterlet spermatogenesis presented in the paper offers an insight into annual reproductive cycles, natural developmental asynchrony of sex cells, and successive transformations of mature and overmature sperm in cysts and excretory duct. Such phased analysis of the development of sex cells, depending on environmental factors (the effect of water temperature) and considering the patterns of spermatogenesis, made it possible to propose the methods to control spermatogenesis in mass spawning. The design of recirculating aquaculture systems makes it possible to control the environmental conditions and spermatogenesis, and promote spawning in sturgeon males in due time, thus ensuring high-quality reproductive products whenever the farm need them. The histological analysis has not only offered an insight into the gonadal maturity parameters, but also, with partial cyst emptying, has allowed detailed characterization of the development of sex cells in spermatogenesis. Understanding the reproductive capacity of males under various housing conditions will allow defining the timing and duration of spawning, i.e., the prespawn, spawning, and postspawn periods of the annual cycle in sterlet.

Reproductive adaptations of sea urchins with planktotrophic larvae

The brief review summarizes the authors' original data on the role of environmental factors in triggering and synchronization of spawning in natural populations of two species of sea urchins with planktotrophic larvae. It is shown that both species exhibit similar reproductive adaptations aimed at enhancing reproductive success. The high sensitivity of sea urchins, primarily males, to environmental signal(s), most likely to phytoplankton, can be considered as a large-scale adaptation characteristic of many marine invertebrates with external fertilization and planktotrophic larvae and promoting the development of mass spawning events. Night time, as well as the new moon and full moon phases, are modulating factors that increase the likelihood of mass spawning. Longer duration of spawning in males compared to females, longer duration of sperm release during mass spawning compared to that during solitary spawning, longer duration of spawning in males living in an environment with higher level of phytoplankton, and approach of males and females during mass spawning can be considered as small-scale adaptations that increase the likelihood of fertilization.

Morphophysiological features of producers of carp cultivated in the pond of the UOKH KSTU

The purpose of this study was to study morphophysiological signs in fish from the brood stock of carp grown in the educational and experimental farm of KSTU. The object of the study was fish from the senior repair group entering the breeding stock for the first time. The research was carried out during the spring fishing of winter repair ponds. Clinically healthy individuals with no abnormalities in the development of the body, fins and head were selected for the representativeness of the studies. Morphophysiological indicators of fish were evaluated using the method of morphophysiological indicators. After determining the exterior and meristic features of the fish, they were opened, determining the mass of internal organs and the length of the intestine. Based on these studies, the indices of internal organs and intestines were calculated according to standard methods. The value of the index of intestinal length in female carp averaged 158.77, and in males 198.75%. The ratio of the anterior part of the swim bladder to the posterior is 1.13 in females, and 1.12 in males. The study of organ indices showed that for females the spleen index was 0.76, for males 0.75%; the gill index was 4.34% for females, 4.13% for males; the liver index is 4.76 and 3.05%, respectively. The gonadosomatic index (GSI) for female carp averaged 50.32%, for males 26.59%. Thus, when analyzing morphophysiological indicators in the first-time spawning males and females of carp, it was found that in terms of the index of intestinal length and the relative length of the intestine, as well as the ratio of the chambers of the swim bladder, the producers of carp grown at the KSTU g are close to “wild” carp or carp. This is probably the result of the specific growing conditions at this enterprise. All values of other morphophysiological indicators in the studied carp producers can be considered satisfactory.

Loss of Nobox prevents ovarian differentiation from juvenile ovaries in zebrafish.

As a species without master sex-determining genes, zebrafish displays high plasticity in sex differentiation, making it an excellent model for studying the regulatory mechanisms underlying gonadal differentiation and gametogenesis. Despite being a gonochorist, zebrafish is a juvenile hermaphrodite that undergoes a special phase of juvenile ovary before further differentiation into functional testis and ovary. The mechanisms underlying juvenile ovary formation and subsequent gonadal differentiation remain largely unknown. In this study, we explored the role of Nobox/nobox (new born ovary homeobox protein), another oocyte-specific transcription factor in females, in early zebrafish gonadogenesis using CRISPR/Cas9 technology. As in mammals, nobox is specifically expressed in zebrafish gonads with a dimorphic pattern at juvenile stage. In contrast to the mutant of figla (factor in the germline alpha, another oocyte-specific transcription factor), the nobox mutants showed formation of typical perinucleolar (PN) follicles at primary growth (PG) stage in juvenile gonads, suggesting occurrence of follicle assembly from cystic oocytes (chromatin nucleolar stage, CN). These follicles, however, failed to develop further to form functional ovaries, resulting in all-male phenotype. Despite its expression in adult testis, the loss of nobox did not seem to affect testis development, spermatogenesis and male spawning. In summary, our results indicate an important role for Nobox in zebrafish ovarian differentiation and early folliculogenesis.

Behaviour affects capture probability by active sampling gear in a cyprinid fish

Animal behaviour interacts with various relationships within biota, and its variation among individuals may cause bias in behavioural research because of its impact on sampling efficiency. In this study, we simultaneously recorded fish behaviour during the reproductive season by passive telemetry and sampled a fish population using an active sampling method by boat electrofishing. A total of 1479 individuals of the cyprinid fish asp (Leuciscus aspius) were tagged, and their reproductive behaviour was recorded using passive telemetry systems in 2015–2020. We investigated whether capture probability was related to fish behaviour during reproduction (length of spawning, number of individual visits to spawning grounds, proportion of time spawning, arrival date and average daily arrival time). Overall, males were more likely to be captured than females (30 ± 4% standard error (SE) vs. 20 ± 3% SE probability) when present in the area. Traits favouring the odds of being captured differed between sexes and included the length of presence, proportion of time invested in spawning and average daily arrival time in males; in females, the capture probability was related to the length of presence and arrival date. This study suggests that even a large sample obtained using active gear may not represent the entire population’s behaviour because of behavioural-related bias in a population.

Indigenous sex-selective salmon harvesting demonstrates pre-contact marine resource management in Burrard Inlet, British Columbia, Canada

To gain insight into pre-contact Coast Salish fishing practices, we used new palaeogenetic analytical techniques to assign sex identifications to salmonid bones from four archaeological sites in Burrard Inlet (Tsleil-Waut), British Columbia, Canada, dating between about 2300–1000 BP (ca. 400 BCE–CE 1200). Our results indicate that male chum salmon (Oncorhynchus keta) were preferentially targeted at two of the four sampled archaeological sites. Because a single male salmon can mate with several females, selectively harvesting male salmon can increase a fishery’s maximum sustainable harvest. We suggest such selective harvesting of visually distinctive male spawning chum salmon was a common practice, most effectively undertaken at wooden weirs spanning small salmon rivers and streams. We argue that this selective harvesting of males is indicative of an ancient and probably geographically widespread practice for ensuring sustainable salmon populations. The archaeological data presented here confirms earlier ethnographic accounts describing the selective harvest of male salmon.

Quantitative study of the behavior of two broadcast spawners, the sea urchins Strongylocentrotus intermedius and Mesocentrotus nudus, during mass spawning events in situ.

BackgroundThe spatial distribution of spawners and temporal parameters of spawning in motile invertebrates with external fertilization might influence reproductive success. However, to date, data on the prespawning and spawning behaviors of broadcast spawners in the field have been scarce and mostly qualitative. The present study was intended to clarify the behavioral adaptations of two sea urchin species, Strongylocentrotus intermedius and Mesocentrotus nudus, using quantitative analysis of their behavior during mass spawning events under natural conditions.MethodsWe analyzed in situ video recordings of sea urchin behavior obtained during six spawning seasons (2014–2019). The total number of specimens of each sea urchin species and the numbers of spawning males and females were counted. Quantitative parameters of sea urchin spawning (numbers of gamete batches, release duration of one gamete batch, time intervals between gamete batches and total duration of spawning) and movement (step length of spawners and nonspawners before and during spawning and changes in distances between males/nonspawners and females) were determined.ResultsFor each species, 12 mass spawning events were recorded in which 10 or more individuals participated. The temporal dynamics of the numbers of males and females participating in mass spawning were well synchronized in both species; however, males began to spawn earlier and ended their spawning later than females. In both species, the most significant intersex difference was the longer spawning duration in males due to the longer pause between gamete batches. The total duration of gamete release did not differ significantly between sexes. The average duration of sperm release during mass spawning events was longer than solitary male spawning. Males and females showed significant increases in the locomotion rate 35 min before the start of spawning and continued to actively move during spawning. An increase in movement rate before spawning in males and females was induced by environmental factor(s). Nonspawners of both species showed increased locomotion activity but in the presence of spawning neighbors and less prominently than spawners. On a vertical surface, both echinoids moved strictly upward. On flat surfaces, males, females and nonspawners of both echinoids became closer during spawning.DiscussionWe showed that two sea urchin species with planktotrophic larvae display similar behavioral adaptations aimed at enhancing reproductive success. The high sensitivity of sea urchins, primarily males, to some environmental factors, most likely phytoplankton, may be considered a large-scale adaptation promoting the development of mass spawning events. The longer spawning duration in males and increased movement activity before and during spawning in both sexes may be considered small-scale adaptations promoting approach of males and females and enhancing the chances of egg fertilization.

Fore reef location influences spawning success and egg predation in lek-like mating territories of the bird wrasse, Gomphosus varius

Many fish spawn in aggregations, but little is understood about the dynamics governing the success of spawning interactions. Here, we evaluate the influence that location of lek-like mating territories has on spawning interactions of Gomphosus varius. We used direct observations of spawning and egg predation events as well as local population counts to compare the rates of spawning, spawning interruptions, and predation on the eggs of G. varius at Finger Reef, Apra Harbor, Guam. We hypothesized that spawning rates would be highest among seaward locations that facilitate transport of pelagic larvae from reefs and that those territories would subsequently experience higher densities of egg predators, egg predation rates, and spawning interruptions. Male spawning success was highly skewed by mating territory location, with holders of the outer, seaward mating territories being more successful than those males holding territories in the middle and inner areas of the aggregation site. Within the outer territories, male mating success was also skewed by location. Egg predation was observed occasionally and increased linearly with bird wrasse spawning frequency. The population densities of egg predators were distributed equally across the study area. Spawning interruptions occurred most frequently within the inner zone of the spawning aggregation due to greater male-male aggression in intraspecific competition for females and territories. This study provides evidence that reef location influences the spawning success, egg predation rates, and spawning interruption rates of fishes that reproduce using lek-like mating territories.

Improving the technology of reproduction of channel catfish Ictalurus punctatus (Raf.) in the conditions of warm-water fisheries

In the process of work on the reproduction of the channel catfish Ictalurus punctatus (Raf.) In the conditions of LLC «Belovsky Fish Industry», the main problem was the timely production of high-quality offspring, associated with differences in preparation for spawning of females and males. In this regard, the purpose of the work: to develop and test various options for carrying out spawning campaigns, including those using various drugs for hormonal stimulation of manufacturers. The results of testing Nerestin preparations in 2006–2008 are presented. In 2006, the drug Nerestin-5x (N5x) was tested. The main problem was identified: 80% of the injected females matured, but the passive males did not start fertilization. It was proposed to adjust the total dose of H5x for females towards a decrease, depending on the degree of their initial readiness, and for males — towards an increase. In 2007, drugs H5x and H7A were tested. A change in the injection scheme of males in 2007 compared to 2006 (an increase in the total dose to the norm of females, but with the use of the drug H5x, and not H6A or H7A during the first two injections) increased the readiness of males for spawning slightly. In 2008, males were brought into the hatchery one month earlier than females, increasing the maturation period of males and changing the temperature rise schedule to prepare for spawning. The drug H7A was used. Despite the increase in the total dose of H7A for males to the total dose for females, their readiness for spawning was still insufficient. To a greater extent, the readiness of males was influenced by an increase in the period of keeping and feeding. The conclusion is drawn that preparations H7 and H7A are quite applicable for artificial reproduction of channel catfish, but the technique of application must be improved by adjusting the conditions of pre-spawning maintenance of producers and the injection scheme.

A Genetic Assessment of Parentage in the Blackspot Sergeant Damselfish, Abudefduf sordidus (Pisces: Pomacentridae)

Microsatellite markers were used to investigate the reproductive behavior of the damselfish Abudefduf sordidus at Johnston Atoll, Central Pacific Ocean. Genetic results indicated that ten males maintained guardianship over their nest territories for up to nine nest cycles during a 3.5 month period. Genotypes of 1025 offspring sampled from 68 nests (composed of 129 clutches) were consistent with 95% of the offspring being sired by the guardian male. Offspring lacking paternal alleles at two or more loci were found in 19 clutches, indicating that reproductive parasitism and subsequent alloparental care occurred. Reconstructed maternal genotypes allowed the identification of a minimum of 74 different females that spawned with these ten territorial males. Males were polygynous, mating with multiple females within and between cycles. Genetic data from nests, which consisted of up to four clutches during a reproductive cycle, indicated that each clutch usually had only one maternal contributor and that different clutches each had different dams. Females displayed sequential polyandry spawning with one male within a cycle but switched males in subsequent spawning cycles. These results highlight new findings regarding male parasitic spawning, polygyny, and sequential polyandry in a marine fish with exclusive male paternal care.

Identification and Function of GnRH-like Peptide in the Pacific Abalone, Haliotis discus hannai.

Gonadotropin-releasing hormone (GnRH) is an important regulator of reproductive function in various vertebrates and invertebrates. In the present study, we have identified the GnRH-like peptide cDNA and peptide from the cerebral ganglion (CG) of the Pacific abalone, Haliotis discus hannai. Pacific abalone GnRH-like peptide (hdhGnRH-like peptide) cDNA encodes precursor, which possesses the typical organization of the known mollusk GnRH-like peptide precursors, including a hydrophobic signal peptide, GnRH-like peptide, and a cleavage site followed by a GAP-like peptide region. Three hdhGnRH-like peptides, pQNYHFSNGWHAamide (hdhGnRH-11amide), pQNYHFSNGWHA (hdhGnRH-11OH), and pQNYHFSNGWHAG (hdhGnRH-12OH), were determined from the acid/acetone extract of the CG by mass spectrometry (LC-MS/MS) analysis. The hdhGnRH-like peptide mRNA expression was detected not only in the CG but also in gonads, and hdhGnRH-11amide was also detected in the extract of gonads. The mRNA expression of hdhGnRH-like peptide in the CG was lower in spawned males than in non-spawned animals, while no change in hdhGnRH-like peptide mRNA expression was shown in both ovulated and non-ovulated abalone. The hdhGnRH-11amide induces spawning and ovulation of both mature males and females in a concentration-dependent fashion following intramuscular injection. These results indicate that three hdhGnRH-like peptides are yielded from a single hdhGnRH-like peptide precursor, and that at least hdhGnRH-11amide is involved in the control of reproduction of the Pacific abalone.

Molecular characterization of gonadotropin-inhibitory hormone (GnIH) gene and effect of intramuscular injection of GnIH peptide on the reproductive axis in Catla catla

Gonadotropin-inhibitory hormone (GnIH) plays an important role in reproduction by inhibiting the expression of gonadotropins in birds and mammals, but in fishes, it is ambiguous. In this study, we cloned 606 bp long cDNA of GnIH from Catla catla brain (cGnIH). The encoded preproGnIH peptide generated three putative peptides (cGnIH-I, -II, -III) of different size. Phylogenetic analysis of GnIH showed clustering of different peptide sequence with its orthologs in separate clades. The real-time PCR analysis showed the expression of cGnIH in brain, gonads, intestine, stomach, heart, gill and liver with the highest expression in the brain and gonads of both sexes. The basal GnIH mRNA expression was higher in spawning and spent phase of the male brain and spawning phase of the female brain. In testis, the expression was highest in spent phase, while in ovary the expression did not change significantly during reproductive phases. The in vivo experiment of cGnIH-III peptide exhibited the higher expression of HPG axis genes, lhb, fshb, cgnrh, kiss2 and kiss1r and serum hormone level of LH and FSH as soon as 3 h after the intramuscular delivery. These results suggest that the GnIH is positively involved in regulation of reproduction in HPG axis of C. catla.

Releasing small ejaculates slowly increases per-gamete fertilization success in an external fertilizer: Galeolaria caespitosa (Polychaeta: Serpulidae)

The idea that male reproductive strategies evolve primarily in response to sperm competition is almost axiomatic in evolutionary biology. However, externally fertilizing species, especially broadcast spawners, represent a large and taxonomically diverse group that have long challenged predictions from sperm competition theory-broadcast spawning males often release sperm slowly, with weak resource-dependent allocation to ejaculates despite massive investment in gonads. One possible explanation for these counter-intuitive patterns is that male broadcast spawners experience strong natural selection from the external environment during sperm dispersal. Using a manipulative experiment, we examine how male reproductive success in the absence of sperm competition varies with ejaculate size and rate of sperm release, in the broadcast spawning marine invertebrate Galeolaria caespitosa (Polychaeta: Serpulidae). We find that the benefits of Fast or Slow sperm release depend strongly on ejaculate size, but also that the per-gamete fertilization rate decreases precipitously with ejaculate size. Overall, these results suggest that, if males can facultatively adjust ejaculate size, they should slowly release small amounts of sperm. Recent theory for broadcast spawners predicts that sperm competition can also select for Slow release rates. Taken together, our results and theory suggest that selection often favours Slow ejaculate release rates whether males experience sperm competition or not.

Biodiversity of the microbiota in Spodoptera exigua (Lepidoptera: Noctuidae).

Spodoptera exigua is a serious pest of many agricultural crops. However, the bacterial communities of S. exigua are poorly studied, particularly over their entire life cycle. We aimed to study the biodiversity of the microbiota across the life cycle of S. exigua and to provide a better and obtain insight into new pest control strategies. The bacterial diversity across the life cycle of S. exigua was studied using Illumina MiSeq sequencing of 16S rRNA genes. Spodoptera exigua is dominated by Proteobacteria and Firmicutes, with a total relative abundance of 90·03%. Enterococcus (24·6%), Pseudomonas (12·2%) and Asaia (45·9%) were abundant and active in eggs, while Methylobacterium (18·7%) and Halomonas (16·5%) dominated freshly eclosed larvae. The 3rd and 5th instar larvae were dominated by Enterococcus (76·3 and 62·0%). Pupal stages had the highest microbial diversity. There was no significant difference between newly emerged males and females. Symbionts of eggs were extremely similar and probably vertically transmitted by males during mating. The result showed that the bacterial community was affected by the host developmental stages. Our results also suggest that symbionts of egg mass are probably vertically transmitted control by male spawning adults. Our study documents the symbiont bacteria across the life cycle of S. exigua. Understanding the microbial symbionts may provide clues to develop potential biocontrol techniques against this pest.

Sperm quality analysis of normal season (NG) and out-season by photoperiod manipulation (PG) of male rainbow trout broodstock (Oncorhynchus mykiss)

Sperm quality parameters in rainbow trout (Oncorhynchus mykiss) were investigated during normal season spawning (November-January) and out-season spawning (July-August) treated with artificial photoperiod manipulation. Normal spawning males (n = 15) were kept in an open concrete pond under natural condition. Out-season spawning males (n = 15) were treated with artificial LED light (50lm/m2) in a closed concrete pond. In these two experimental groups, five fish were used in each of three spawning periods. The mean weight and body length of males (2 + years, n = 30) were 1213.43 ± 39.43g and 45.08 ± 0.62cm, respectively. Sperms were collected from July to August 2016 in the out-season spawning or photoperiod-manipulated group (PG) (water temperature 14.21 ± 0.31°C) and from December 2016 to January 2017, in the normal season spawning group (NG) (water temperature 8.81 ± 1.03°C). Volume of sperm, osmolality of seminal plasma, density of sperm, percentage of motile spermatozoa (MOT), curvilinear velocity (VCL), and duration of motility were measured for each male. Seminal plasma osmolality, density of sperm, and the motility of duration were 358.47 ± 37.24 and 308.87 ± 44.09, 4.37 ± 2.10 and 9.8 ± 1.56, and 8.8 ± 2.42 and 24.6 ± 6.76 in PG and NG, respectively. Fertilization rate was 37.79 ± 9.37% and 94.51 ± 1.33% in PG and NG, respectively. Sperm quality parameters showed significant differences in most of the cases (p < 0.05) and fertilization rate at eyed egg stage (150-160 degree-days) was significantly higher in normal season spawning group than the photoperiod-manipulated group (p < 0.05). Though the rate of fertilization was low in out-season, it was able to get enough gametes in summer using only artificial light having no changes in other parameters.

Predicting impacts of chemicals from organisms to ecosystem service delivery: A case study of endocrine disruptor effects on trout

We demonstrate how mechanistic modeling can be used to predict whether and how biological responses to chemicals at (sub)organismal levels in model species (i.e., what we typically measure) translate into impacts on ecosystem service delivery (i.e., what we care about). We consider a hypothetical case study of two species of trout, brown trout (Salmo trutta; BT) and greenback cutthroat trout (Oncorhynchus clarkii stomias; GCT). These hypothetical populations live in a high-altitude river system and are exposed to human-derived estrogen (17α‑ethinyl estradiol, EE2), which is the bioactive estrogen in many contraceptives. We use the individual-based model inSTREAM to explore how seasonally varying concentrations of EE2 could influence male spawning and sperm quality. Resulting impacts on trout recruitment and the consequences of such for anglers and for the continued viability of populations of GCT (the state fish of Colorado) are explored. inSTREAM incorporates seasonally varying river flow and temperature, fishing pressure, the influence of EE2 on species-specific demography, and inter-specific competition. The model facilitates quantitative exploration of the relative importance of endocrine disruption and inter-species competition on trout population dynamics. Simulations predicted constant EE2 loading to have more impacts on GCT than BT. However, increasing removal of BT by anglers can enhance the persistence of GCT and offset some of the negative effects of EE2. We demonstrate how models that quantitatively link impacts of chemicals and other stressors on individual survival, growth, and reproduction to consequences for populations and ecosystem service delivery, can be coupled with ecosystem service valuation. The approach facilitates interpretation of toxicity data in an ecological context and gives beneficiaries of ecosystem services a more explicit role in management decisions. Although challenges remain, this type of approach may be particularly helpful for site-specific risk assessments and those in which tradeoffs and synergies among ecosystem services need to be considered.

REPRODUCTIVE ASPECTS OF THE TROPICAL ABALONE, HALIOTIS ASININA, FROM SOUTHERN LOMBOK WATERS, INDONESIA

The main objective of this study was to determine reproductive strategy including major spawning season of tropical abalone (Haliotis asinina) from southern Lombok waters, Indonesia. Gonad bulk index, maturity stages and oocyte size frequency distribution were applied to document gonadal development and major spawning season. The results of this study show that H. asinina in southern Lombok waters displayed year-round spawning with a high proportion occurring in August - November, when gonad index dropped to a lower level and high proportion of partly spawned and/or spent ovaries occurred in the population. Gonad development and spawning in males and females occurred synchronously. The correlation between gonadal development and environmental factors are described and discussed.

Environmental and biological cues for spawning in the crown-of-thorns starfish.

Sporadic outbreaks of the coral-eating crown-of-thorns starfish are likely to be due, at least in part, to spatial and temporal variation in reproductive and settlement success. For gonochoric and broadcast spawning species such as crown-of-thorns starfish, spawning synchrony is fundamental for achieving high rates of fertilization. Highly synchronized gamete release within and among distinct populations is typically the result of the entrainment of neurohormonal endogenous rhythms by cues from the environment. In this study, we conducted multiple spawning assays to test the effects of temperature change, reduced salinity and nutrient enrichment of seawater, phytoplankton, gametes (sperm and eggs), and the combined effect of sperm and phytoplankton on the likelihood of spawning in male and female crown-of-thorns starfish. We also investigated sex-specific responses to each of these potential spawning cues. We found that (1) abrupt temperature change (an increase of 4°C) induced spawning in males, but less so in females; (2) males often spawned in response to the presence of phytoplankton, but none of the females spawned in response to these cues; (3) the presence of sperm in the water column induced males and females to spawn, although additive and synergistic effects of sperm and phytoplankton were not significant; and (4) males are more sensitive to the spawning cues tested and most likely spawn prior to females. We propose that environmental cues act as spawning ‘inducers’ by causing the release of hormones (gonad stimulating substance) in sensitive males, while biological cues (pheromones) from released sperm, in turn, act as spawning ‘synchronizers’ by triggering a hormonal cascade resulting in gamete shedding by conspecifics. Given the immediate temporal linkage between the timing of spawning and fertilization events, variability in the extent and synchronicity of gamete release will significantly influence reproductive success and may account for fluctuations in the abundance of crown-of-thorns starfish.