Mass Spawning Research Articles

Fate of genetic diversity within and between generations and implications for DNA parentage analysis in selective breeding of mass spawners: A case study of commercially farmed barramundi, Lates calcarifer

Abstract Mass spawning fish species pose significant challenges for the design and conduct of effective aquaculture breeding programs. This is because the hatchery manager has limited control over the individual contributions of broodstock within a spawn, and consequently, the number and size of families in the resulting progeny cohorts. While early broodstock contributions have been tracked in many mass-spawning species through early development, it is currently unknown if individuals from poorly represented families are lost by the time of harvest due to differential survival, or if they are still available until the critical moment of selection to contribute as parents to the next generation. In addition, there are no studies based on real harvest data that determine how differential contribution and growth of families seen in mass spawners impact on selection of candidate broodstock. This is particularly important to understand, as mixed families in every cohort require the application of costly DNA genotyping analyses to determine pedigrees. In order to assist in the design of selective breeding strategies for mass spawners, barramundi (Lates calcarifer) was used as a model species to evaluate how family survival and growth under skewed contributions may affect the selection of breeding candidates at harvest. In this study, 18 days-post-hatch (dph) larval offspring from three commercial cohorts were firstly genotyped and assigned to their family of origin. Later at harvest (273–469 dph), fish from these cohorts were weighed and genotyped. Results showed that relative family frequencies at harvest were in different proportions than those found in the hatchery phase (P 2.17 S.D. heavier than the population mean) will capture > 75% of family-specific genetic diversity present. Continued sampling after this was ineffective, with each additional 170 fish sampled only returning 1% extra family-specific genetic diversity.

Biology of the Mountain Crayfish Euastacus sulcatus Riek, 1951 (Crustacea: Parastacidae), in New South Wales, Australia

The biology and distribution of the threatened Mountain Crayfish Euastacus sulcatus, was examined through widespread sampling and a long-term mark and recapture program in New South Wales. Crayfish surveys were undertaken at 245 regional sites between 2001 and 2005, and the species was recorded at 27 sites in the Clarence, Richmond and Tweed River drainages of New South Wales, including the only three historic sites of record in the state, Brindle Creek, Mount Warning and Richmond Range. The species was restricted to highland, forested sites (220-890 m above sea level), primarily in national park and state forest reserves. Adult crayfish disappear from the observable population during the cooler months, re-emerging in October when the reproductive season commences. Females mature at approximately 50mm OCL, and all mature females engage in breeding during a mass spawning season in spring, carrying 45-600 eggs. Eggs take six to seven weeks to develop, and the hatched juveniles remain within the clutch for a further 2.5 weeks. This reproductive cycle is relatively short, and represents a more protracted and later breeding season than has been inferred for the species in Queensland. A combination of infrequent moulting and small moult increments indicated an exceptionally slow growth rate; large animals could feasibly be 40-50 years old. Implications for the conservation and management of E. sulcatus are discussed.

The effect of temperature on embryo survival and development in pallid sturgeon Scaphirhynchus albus (Forbes & Richardson 1905) and shovelnose sturgeon S. platorynchus (Rafinesque, 1820)

The thermal response of pallid sturgeon Scaphirhynchus albus and shovelnose sturgeon S. platorynchus embryos was determined at incubation temperatures from 8 to 26°C and 8 to 28°C, respectively. The upper and lower temperatures with 100% (LT100) embryo mortality were 8 and 26°C for pallid sturgeon and 8 and 28°C for shovelnose sturgeon. It was concluded that 12–24°C is the approximate thermal niche for embryos of both species. Generalized additive and additive-mixed models were used to analyze survival, developmental rate and dry weight data, and predict an optimal temperature for embryo incubation. Pallid sturgeon and shovelnose sturgeon embryo survival rates were different in intermediate and extreme temperatures. The estimated optimal temperature for embryo survival was 17–18°C for both species. A significant interaction between rate of development and temperature was found in each species. No evidence was found for a difference in timing of blastopore, neural tube closure, or formation of an S-shaped heart between species at similar temperatures. The estimated effects of temperature on developmental rate ranged from linear to exponential shapes. The relationship for rate of development to temperature was relatively linear from 12°C to 20°C and increasingly curvilinear at temperatures exceeding 20°C, suggesting an optimal temperature near 20°C. Though significant differences in mean dry weights between species were observed, both predicted maximum weights occurred at approximately 18°C, suggesting a temperature optimum near 18°C for metabolic processes. Using thermal optimums and tolerances of embryos as a proxy to estimate spawning distributions of adults in a river with a naturally vernalized thermal regime, it is predicted that pallid sturgeon and shovelnose sturgeon spawn in the wild from 12°C to 24°C, with mass spawning likely occurring from 16°C to 20°C and with fewer individuals spawning from 12 to 15°C and 21 to 24°C. Hypolimnetic releases from Missouri River dams were examined; it was concluded that the cooler water has the potential to inhibit and delay sturgeon spawning and impede embryo incubation in areas downstream of the dams. Further investigations into this area, including potential mitigative solutions, are warranted.

Temporal patterns and behavioral characteristics of aggregation formation and spawning in the Bermuda chub (Kyphosus sectatrix)

Reef fish spawning aggregations are important life history events that occur at specific times and locations and represent the primary mode of reproduction for many species. This paper provides detailed descriptions of aggregation formation and mass spawning of the Bermuda chub (Kyphosus sectatrix). Spawning coloration and gamete release of K. sectatrix were observed and filmed at the Grammanik Bank, a deep spawning aggregation site used by many different species located on the southern edge of the Puerto Rican shelf 10 km south of St. Thomas, US Virgin Islands. Underwater visual surveys using technical Nitrox and closed circuit re-breathers were conducted from December 2002 to March 2013 and documented spatial and temporal patterns of movement and aggregation formation along 1.5 km of mesophotic reef. The largest aggregations of K. sectatrix (>200 fish) were observed on the Grammanik Bank January to March from 0 to 11 d after the full moon with peak abundance from 60 to 80 d after the winter solstice across all survey years. Aggregation formation of K. sectatrix coincided with the spawning season of Nassau (Epinephelus striatus) and yellowfin (Mycteroperca venenosa) groupers. These spatial and temporal patterns of aggregation formation and spawning suggest that K. sectatrix, an herbivore, may also be a transient aggregating species. On several occasions, chubs were observed both pair spawning and mass spawning. Color patterns and behaviors associated with aggregation and spawning are described and compared to spawning characteristics observed in other species, many of which are similar but others that appear unique to K. sectatrix. This represents the first report of a kyphosid species aggregating to spawn and illuminates a portion of the poorly understood life history of the Bermuda chub.

Sibship reconstruction and effective population size estimation in mass spawning ark shell, Scapharca broughtonii based on microsatellite analysis

Five highly polymorphic microsatellite loci were utilized to reconstruct sibship during a mass spawning event of ark shell, Scapharca broughtonii and to estimate the genetic variability between the D-shaped larvae and metamorphosed juvenile stage. The allelic diversity, and observed and expected heterozygosities exhibited similarity between the two sampling stages. The sibship reconstruction results of 180 offspring in each stage demonstrated that the effective population size was 20 in the D-shaped larvae stage and decreased to 16 in the metamorphosed juvenile stage. The inferred number of parents at the metamorphosed juvenile stage decreased 16.13 % and the inbreeding rate increased 0.6 % comparing to the D-shaped larvae stage. Multiple matings were detected both in males and females, and the reproductive success of both sexes in the two stages was positively correlated to the number of individuals with which it had mated. The results lend insight to S. broughtonii cultivation in China and provide a genetic guide for the development of more effective spawning techniques in the future.

Development of new assessment methods for Acropora coral recruitment using coral settlement devices and holes of marine block

We developed new assessment methods for Acropora coral recruitment using coral settlement devices (CSDs) and holes of a marine block. Both devices were deployed in situ before mass spawning of Acropora corals. The CSDs were sampled after 3–4 months of spawning to measure early recruitment, whereas holes of the marine block were observed underwater or MB was sampled to observe holes after 1 year of spawning to measure the recruitment. By combining the results, we would know the recruitment (visually identified underwater) in reefs, including the amount of early recruitment (identified by stereomicroscopic methods), and the environmental condition of the coral reef. These results would help to predict the future of a reef. Nagura Bay had a high early Acropora recruitment; however, due to competition with algae and sedimentation, the recruitment of juvenile corals was extremely low. The reef would possibly be healthy and sustainable at sites where both the early recruitment and recruitment are high. However, if both are low, the reef will be in a critical condition where urgent restoration will be required.

Broodstock contribution after mass spawning and size grading in barramundi (Lates calcarifer, Bloch)

Appropriately designed selective breeding programs are needed to limit the loss of genetic diversity and control levels of inbreeding, and to base selection decisions on data collected from many offspring of many families. Achieving a relatively even contribution by broodstock to subsequent generations is necessary and for many aquaculture species this is possible to control through mate pairing. Barramundi (Lates calcarifer) provides an exception, because it is a species that mass spawn in small groups and whose offspring are repeatedly size graded in an effort to avoid cannibalism. Following mass spawning a large broodstock group of 33 barramundi, levels of parental contribution and multiple measures of genetic diversity were estimated over the course of repeated size grading events. Parentage was inferred using 17 microsatellite DNA loci. Twelve dams and twenty-one sires were artificially spawned over two nights and sampled at 1, 18 and 90days post hatch (dph). Broodstock contributions were skewed and the contribution by individual dams and sires was as high as 48 and 16% respectively at 1dph. Despite the unequal contribution and high variance in family sizes, 31 broodstock were detected as contributing to the spawning events and as a result up to 103 full-sibling families were detected (18dph, n=472). A reduction in allelic richness (Ar) was identified from broodstock to offspring at 1dph, (Ar was 3.94 among broodstock and 3.52 among offspring sampled). However, no further loss of Ar or genetic diversity was detected in the offspring from 1 to 90dph, which included the period of metamorphosis, multiple size grading events and losses through size culling, mortalities and the sale of juveniles. The effective census population size ratio (Ne/Nc) ranged from 0.31 to 0.51 at times of sampling, (Ne was calculated between 10.1 and 16.7, well below the broodstock census size of 33) and the rate of inbreeding was less than 5%. This research provides valuable baseline data that can be used to make recommendations for the maintenance of genetic diversity and control of inbreeding for a barramundi selective breeding program. It also provides an example of what considerations need to be made for the genetic management of mass spawning and/or cannibalistic species.

Heritability of harvest growth traits and genotype–environment interactions in barramundi, Lates calcarifer (Bloch)

Due to its popularity as a food fish, rapid growth and wide environmental tolerances, barramundi, Lates calcarifer, production levels are increasing worldwide and breeding programs are currently being considered and implemented throughout Asia and Australia. However, for selective breeding programs to be effective, it is essential to have information on genetic parameters such as heritability and genetic correlations of traits, as well as on how families perform relative to each other over the culture cycle in single or in multiple environments (ti). Genetic parameters and G×E interactions for barramundi traits (namely weight (W), standard length (Ls), body depth (BD), Fulton's condition factor (K=106W/Ls3) and a body shape index (H=10 BD/Ls)) at 62days post hatch (dph) and at harvest size (273–469 dph) were estimated for the first time for this species based on microsatellite DNA parentage assignment of 3110 offspring generated in three mass spawning events, where up to 121 families were produced per batch. Heritability estimates for growth related traits W, Ls and BD were moderate for fish reared in cages at 62 dph (average h2=0.22, 0.27, 0.15; respectively) and high at harvest for fish reared in intensive tanks and in a semi intensive pond (average h2=0.40, 0.37, 0.40; respectively). Estimates for ratio traits K and H were lower than for growth traits for all ages and environments (average h2 K=0.14 and h2 H=0.09). Genetic and phenotypic correlations between W and Ls, W and BD and Ls and BD ranged from 0.91 to 0.99, whereas correlations involving K and H and other traits (W, Ls and BD) were lower (0.07 to 0.88), but positive, indicating that these traits may also be modified if selection is based on W (or Ls) alone. In addition, no significant G×E interactions for growth related traits W, Ls and BD were detected for barramundi either reared in fresh vs. sea water cages at 62 dph (rg≥0.97), or commercially reared in fresh water until harvest size (343–469 dph) in an intensive recirculation aquaculture system vs. a semi-intensive pond (rg~0.99). High heritability estimates found here show that additive genetic effects play a significant role in barramundi growth, especially in older fish, suggesting that growth rates could be greatly improved through selective breeding.

Mass spawning events, seasonality and reproductive features in Milleporids (Cnidaria, Hydrozoa) from Reunion Island

AbstractThree species of fire corals are present on the fringing coral reefs of Reunion Island (SW Indian Ocean): Millepora exaesa, Millepora platyphylla and Millepora tenera. Compared with scleractinian corals, reproduction studies on milleporids are scarce and this is the first study to be conducted in the Indian Ocean and on M. exaesa. We used a combination of weekly in situ observations and laboratory studies to document reproductive stages and phenology. The sexual reproductive period was the austral summer (Nov–Jan), the maturation of the colonies being correlated to the seasonal increasing water temperature. We describe both ampullae and short‐lived medusae (medusoids), and report differences in the size and density of ampullae and the distribution of nematocysts in the medusoids of the three species. The absence of radial and circular canals in all medusoids agrees with the original description but not with the current diagnosis of the family Milleporidae. We observed the first mass spawning event in M. exaesa and M. platyphylla, and provide the first description of a zooxanthellate Millepora larva. Spawning always began before dark but was not correlated with the lunar or tidal cycles. Millepora tenera colonies released several batches of medusoids during the reproductive period, suggesting that this species may be a serial spawner.

Microsatellites markers to depict the reproductive and genetic patterns of farmed gilthead seabream (Sparus aurata): illustration by a case study on mass spawning

In the absence of breeding strategy, natural spawning constitutes the breeding ground for fish farmers to empirically manage their commercial broodstock. In this context, we used six microsatellite markers to characterize the genetic pattern of six commercial seabream broodfish tanks having a common history spanning four generations. The progeny of one tank single-day mass-spawning event, reared in two different environments, was used to estimate the genetic parameters for body weight. Limited genetic differentiation was observed among broodfish groups. A panel of nine loci allowed us to unambiguously assign 95.4% of the offspring (1692) and identify 37 parents (65% of the total broodfish). The limited effective population size (Ne = 15.3) was due to the elevated variance of parental contributions and to broodfish failing to contribute to the progeny. The fluctuation of the allele frequency highlighted the risks of genetic drift and reduction in the heterozygosity in the next generations. Heritability for body weight was moderate at commercial size (0.40 ± 0.10) and the high genetic correlation at later stages laid the groundwork for precocious selection criteria for growth. The discussion opens on the opportunity to use mass spawning for selective breeding.

Is monitoring for mass spawning events in coral assemblages in north Western Australia likely to detect spawning?

In north Western Australia coral reefs occur near ports being developed to support rapidly expanding resources industries. Dredging for port construction is required to stop during significant mass coral spawning events due to the sensitivity of gametes and larvae to increases in turbidity and sedimentation, but the timing of this event can vary between seasons and years so monitoring is used to predict when spawning is imminent. Here we used simulations to mimick sampling strategies currently used in some coral spawning monitoring programmes in Western Australia, to assess the ability of these programmes to be able to predict multi-specific mass spawning events. We found that current practices may sometimes miss spawning events that are likely to be considered large enough to warrant stopping dredging. Generally, sampling fewer individuals in a large number of species is a better way of monitoring for upcoming spawning than sampling a large number of individuals in a small number of species, but overall, greater sampling efforts than are currently undertaken are needed if moderately sized events are to be detected reliably. Determining exactly how many samples are needed, however, depends on having a clearer definition of what actually constitutes a “significant mass spawning” event in the first place.

Genetic Diversity of Cultured, Naturalized, and Native Pacific Oysters,Crassostrea Gigas, Determined from Multiplexed Microsatellite Markers

Ten polymorphic microsatellite loci were multiplexed to analyze a total of 343 Pacific oysters (Crassostrea gigas) sampled from native (Japan and Korea), naturalized (France and Australia), and cultured (3 Australian programs) populations. Genetic diversity was high within the native and naturalized populations (average allelic richness, 18.7; expected heterozygosity, 0.89), but lower within samples from hatchery populations (allelic richness, 12.3; expected heterozygosity, 0.84). A significant decrease in diversity was found within Australian cultured populations. However, diversity was shown to be similar in samples from a well-managed, family-based selective breeding population and commercial hatchery mass spawning populations. The Bayesian analysis of population structure found no difference between native and naturalized samples, which, together with other results, indicate that the naturalized populations have not changed genetically since their introduction. This suggests that naturalized populations can provide a good source of genetic diversity for breeding programs.

Using larval dispersal simulations for marine protected area design: Application to the Gulf of Lions (northwest Mediterranean)

The design (location and size) of sustaining, no‐take reserves was investigated by combining realistic numerical simulations of larval dispersal from a sedentary marine species with a population dynamics model. The method explored, a priori: (1) the planktonic larval duration (PLD) of self‐persistent populations within no‐take reserves with radii from 1 to 20 km, (2) the size of a no‐take reserve reaching self‐persistent recruitment of the reserve population, and (3) offspring spillover to adjacent fisheries for PLDs from 1 to 6 weeks. In the Gulf of Lions (northwest Mediterranean), as the radius of a no‐take reserve increased to 20 km, the median PLD of a self‐persistent species within the reserve increased from 2 to 6.5 d. No unique relation between PLD and sustaining no‐take reserve size could be established because of large spatial and temporal variabilities, thus precluding any general guidelines for marine protected area sizes. For species with mass spawning lasting < 3 d, variability due to spawning timing yielded twice the spatial variability, reflecting strong wind variability. In contrast, when spawning lasted more than 10 d, the spawning location became more important. Thus, a biological process (spawning duration) can trigger deterministic and stochastic effects of environmental variability. Finally, some unprotected areas (Narbonne to Agde and the Camargue) clearly appeared to be better locations than the existing no‐take reserves for maximizing biodiversity persistence within a reasonable no‐take reserve size (10 to 20 km) and for producing offspring spillover important for regional fisheries (80%).

Population consequences of mass coming of pink salmon Oncorhynchus gorbuscha to the Northeastern Coast of Kamchatka in 2009

During mass spawning of pink salmon Oncorhynchus gorbuscha in two rivers of central Karaginskii Bay (Kamchatka), the average coverage of the spawning hillock did not vary much (0.6–0.7 m2) even though the abundance of the spawning adults varied greatly. When the abundance of spawning females was less than 1.4 ind. per m2 of spawning ground, the spawning hillocks did not interlock. When the abundance of spawning females varied from 1.7 to 1.8 ind./m2, the spawning hillocks interlocked, and approximately 20–25% of them were re-excavated. When the abundance of spawning females was higher than 2.0 ind./m2, all the early-deposited spawning hillocks were re-excavated. The re-excavation of the spawning hillocks increased the population mortality also by the mass pre-spawning death of the breeders and spawning outside the spawning grounds. Meanwhile, fish-kill of the eggs in the spawning hillocks was not observed, and the mortality of embryos and larvae did not depend on the spawning intensity. The ratio of live and dead embryos in the spawning hillocks before their hatching was approximately 60%, varying from 44 up to 92% in regard to the environment of the spawning ground (autumn low water, freezing, and siltation). Significant correlation was found between the survivability and grain-size composition of the spawning hillocks when the impact of small-size fraction was a limiting factor.

From Parent to Gamete: Vertical Transmission of Symbiodinium (Dinophyceae) ITS2 Sequence Assemblages in the Reef Building Coral Montipora capitata

Parental effects are ubiquitous in nature and in many organisms play a particularly critical role in the transfer of symbionts across generations; however, their influence and relative importance in the marine environment has rarely been considered. Coral reefs are biologically diverse and productive marine ecosystems, whose success is framed by symbiosis between reef-building corals and unicellular dinoflagellates in the genus Symbiodinium. Many corals produce aposymbiotic larvae that are infected by Symbiodinium from the environment (horizontal transmission), which allows for the acquisition of new endosymbionts (different from their parents) each generation. In the remaining species, Symbiodinium are transmitted directly from parent to offspring via eggs (vertical transmission), a mechanism that perpetuates the relationship between some or all of the Symbiodinium diversity found in the parent through multiple generations. Here we examine vertical transmission in the Hawaiian coral Montipora capitata by comparing the Symbiodinium ITS2 sequence assemblages in parent colonies and the eggs they produce. Parental effects on sequence assemblages in eggs are explored in the context of the coral genotype, colony morphology, and the environment of parent colonies. Our results indicate that ITS2 sequence assemblages in eggs are generally similar to their parents, and patterns in parental assemblages are different, and reflect environmental conditions, but not colony morphology or coral genotype. We conclude that eggs released by parent colonies during mass spawning events are seeded with different ITS2 sequence assemblages, which encompass phylogenetic variability that may have profound implications for the development, settlement and survival of coral offspring.

Coral-Bacterial Communities before and after a Coral Mass Spawning Event on Ningaloo Reef

Bacteria associated with three coral species, Acropora tenuis, Pocillopora damicornis and Tubastrea faulkneri, were assessed before and after coral mass spawning on Ningaloo Reef in Western Australia. Two colonies of each species were sampled before and after the mass spawning event and two additional samples were collected for P. damicornis after planulation. A variable 470 bp region of the 16 S rRNA gene was selected for pyrosequencing to provide an understanding of potential variations in coral-associated bacterial diversity and community structure. Bacterial diversity increased for all coral species after spawning as assessed by Chao1 diversity indicators. Minimal changes in community structure were observed at the class level and data at the taxonomical level of genus incorporated into a PCA analysis indicated that despite bacterial diversity increasing after spawning, coral-associated community structure did not shift greatly with samples grouped according to species. However, interesting changes could be detected from the dataset; for example, α-Proteobacteria increased in relative abundance after coral spawning and particularly the Roseobacter clade was found to be prominent in all coral species, indicating that this group may be important in coral reproduction.

Effect of suspended sediment on fertilization success in the scleractinian coral Pectinia lactuca

The effect of increased levels of suspended sediment on fertilization success in the scleractinian coral Pectinia lactuca was investigated in a laboratory experiment following a mass coral spawning event on reefs off Singapore. Egg–sperm bundles were collected from tank-spawned coral colonies collected from the field several days prior to the anticipated mass spawning. Eggs and sperm from each colony were separated and distributed systematically across replicated treatments (N = 9) with three concentrations of fine suspended sediment. Spawning and embryo development in Pectinia lactuca followed a pattern similar to other scleractinian coral species. There was a significant effect of increased suspended sediment concentration on fertilization success (P < 0.05). Both high- (169 mg l−1) and medium- (43 mg l−1) suspended sediment treatments decreased fertilization success compared to controls. These results imply that increased turbidity levels (whether chronic, such as in the waters around Singapore, or short-term, caused by a dredging operation)—when coinciding with the coral spawning season—may affect the reproductive success of corals and compromise coral recruitment and recovery of degraded reefs.

Mating Systems and Reproductive Success in Hermaphroditic Bay Scallop, Argopecten irradians irradians (Lamarck 1819), Inferred by Microsatellite‐based Parentage Analysis

In this study, we used microsatellite‐based parentage analysis to assess the mating system of a mass spawning bay scallop, Argopecten irradians irradians. Parental assignment was performed on 237 offspring and 14 candidate parents. Overall, 95% of all offspring were unambiguously allocated to their putative parents based on information from six highly polymorphic loci. Offspring from both the self‐fertilization and cross‐fertilization style were observed, the large variation of self‐fertilization rate among individuals displays a mixed mode of mating. The high variances in reproductive success resulted in a decline in effective breeding numbers (Nb/N = 0.71). The self‐fertilization rate was 32.89% for this mass spawning and the coefficient of inbreeding was estimated at around 16.5% per generation. When selfed larvae were removed, the relationship between relatedness and individual reproductive success was proved insignificant between half‐sibings and unrelated, which suggest that selection pressures other than avoidance of inbreeding may be responsible for the evolution and maintenance of the self‐compatible mating system of A. i. irradians. These results lend insight to A. i. irradians cultivation in present China and provide a genetic basis for the development of more effective spawning techniques.

Salmonid influences on rivers: A geomorphic fish tail

Studies of the effects of salmonids on the environment have focused primarily on the biological linkages between salmon runs and stream ecology. Less effort has focused on geomorphic effects. A review of the literature indicates potential (i) direct effects in response to mass spawning of salmonids, including changes in streambed and bank morphology and annual volumes of bedload transported; and (ii) indirect effects including supply of nutrients to the riparian zone, which may influence the in-channel dynamics of large woody debris and bank stability, and effects on population density of net-spinning caddisfly larvae which may influence streambed stability in finer gravel substrates. More research is needed over long time frames, however, to ascertain whether such effects are geomorphically significant at larger spatial and longer temporal scales, and to estimate the sizes of populations required to cause geomorphically significant responses. Some possible studies are suggested.

On reproduction of longfin thornyhead Sebastolobus macrochir (Scorpaeniformes: Sebastidae) in waters off the eastern coast of the Kurils

According to data obtained off the eastern coast of the Northern Kurils in October–December 1998, the body length of spawning females of the longfin thornyhead Sebastolobus macrochir is 26–41 cm (on average, 31.5 ± 0.27). Mass spawning is recorded in females 28 cm in length and longer. The individual absolute fecundity of females is 69355-411710 (on average, 189086 ± 13662) eggs. The reproductive potential of females of the longfin thornyhead is estimated as 189 million eggs. It is supposed that all females participate in spawning.