Presence Of Postovulatory Follicles Research Articles

Recent Findings on Spawning Patterns and Recommendations for the Fishery Management of the Southern Red Snapper—Lutjanus purpureus (Poey, 1866)—On the Amazon Continental Shelf of Brazil

The southern red snapper, Lutjanus purpureus, is one of the primary fishery resources of the Amazon continental shelf. Due to the demand for specimens of less than 900 g in weight, increased fishing effort focusing on this size class has led to a drastic decrease in catches. The present study was based on the analysis of cellular structures in the female gonads (formation of oocytes and other reproductive tissues) to identify reproductive processes and evaluate the effectiveness of current fishery management practices. The presence of postovulatory follicles (POFs) peaked in April, which was interpreted as a period of intense spawning. In addition to POFs, hydrated oocytes peaked in July, indicating either reproductive continuity or a second peak, based on the presence of atretic oocytes and atresia. Given that the local snapper fishery preferentially targets very young individuals, an extension of the closed season from March to July would be recommendable to guarantee the reproductive potential of the spawning stock.

Oocyte development, packing in the ovary, and spawning pattern of squid Lolliguncula panamensis in the Mexican South Pacific

Squid Lolliguncula panamensis Berry, 1911 is of commercial and ecological importance in the Gulf of Tehuantepec (southeastern Mexico). This study examines the mode of oocyte development, packing in the ovary, and spawning pattern of this understudied species. Lolliguncula panamensis presents a synchronous oocyte growth in batches, with multiple spawnings, with the presence of post-ovulatory follicles and atretic follicles, including the constant presence of pre-vitellogenic and vitellogenic oocytes. The size frequencies of oocytes of ripe ovaries exhibit a pronounced morphological and size separation between the late yolk stage and mature oocytes, suggesting that the oocytes pass through this size range very fast. These oocytes adopt a geometrical shape that makes their packing efficient for spawning. One three-dimensional packing of vitellogenic oocytes (scutoid type) in the ovary was observed. The results of our study suggest that the spawning behavior of Lolliguncula panamensis may constitute an opportunistic reproductive strategy in which individuals present multiple spawnings over a brief period. We suggest that this strategy might be a response to complex regional oceanographic conditions of the Gulf of Tehuantepec.

Variation in reproductive parameters of round herring in the Pacific coastal waters of Japan

This study assessed potential variability in batch fecundity and the spawning fraction of round herring Etrumeus micropus in the Pacific coastal waters of Japan. Fish were caught by a research vessel in the Kumano Nada (Kumano Sea) and Tosa Bay in February 2016, and other fish caught by commercial vessels in the Kumano Sea were collected between January 2019 and February 2020. The appearance of hydrated oocytes in the 2016 samples indicated that the fish spawned between midday and evening in the Kumano Sea, whereas they spawned from daytime to nightfall in Tosa Bay. The spawning fraction was estimated using the 2016 samples and was based on presence of post-ovulatory follicles and oocytes during oocyte maturation. The spawning fraction and spawning interval, respectively, were similar between the two areas: 0.17–0.26 and 3.9–5.9 d in the Kumano Sea, and 0.14–0.53 and 1.9–7.0 d in Tosa Bay. Batch fecundity was estimated by counting oocytes during oocyte maturation. The relationships of batch fecundity to body length varied significantly among the monthly samples. Batch fecundity at a given body length increased from January to May. This indicates that the acceleration in individual egg production would have contributed to the increase in egg abundance during the main spawning period. Relative batch fecundity (RBF) ranged from 76 to 142 eggs g−1 of ovary-free female. The 2016 samples showed that RBF was higher in Tosa Bay than in the Kumano Sea. The RBF increased from January to April in the Kumano Sea. A comparison of RBF values for the same month (February) differed significantly between samples in the three years, suggesting inter-annual variation in RBF. Our data provide essential information for understanding the spawning ecology of round herring and for allowing the egg production method to be applied to estimates of stock biomass.

Ovarian maturation of Penaeus subtilis (Decapoda: Penaeidae): A new insight to describe oocyte development and somatic structures

AbstractWe observed the presence of follicular cells (FC) in the ovaries of Penaeus subtilis (n = 1198), which led us to classify the development of germ cells into six phases: oogonia, previtellogenic oocytes, primary and secondary vitellogenic oocytes, mature oocytes and atretic oocytes. The FC changes their shape according to the development of germ cells and showed a different distribution along the ovary, which allowed differentiating vitellogenic oocytes into primary and secondary. We also observed that the postovulatory follicles (POF) are composed of follicular cells. The presence of POF in penaeids ovaries is rarely reported, but allows the differentiation between spent and resting stages, commonly grouped in reproductive biology research. Furthermore, observation of ovarian lining was useful to differentiate immature females from females that had spawned at least once. Thus, ovarian development was classified into six stages: immature, early developing, advanced developing, ripe, spent and resting. The distribution and shape variations of FC, ovarian lining features and presence of POF were considered crucial for the classification of ovarian maturation stages. The methods developed here may improve estimates of their reproductive cycle, size at first maturity and spawning season, which are important variables in future studies of the reproductive dynamics.

Direct evidence of a spawning aggregation of cubera snapper (Lutjanus cyanopterus) in southeastern Brazil and its management implications

Identifying fish spawning aggregations is crucial to determine effective fisheries management measures and protect key reproduction sites. We found direct evidence (the presence of post-ovulatory follicles) of a spawning aggregation of cubera snapper (Lutjanus cyanopterus) within the largest multiple-use marine protected area in southeastern Brazil, representing the first in-situ validation of a cubera snapper spawning aggregation in subtropical waters off the southwestern Atlantic. Out of 127 specimens (weighing ~ 2253 kg total) illegally caught by a fishing vessel on January 17th, 2021, fourteen individuals, ranging from 82 to 115.4 cm, were randomly selected and analyzed. The histological examination of six ovaries showed spawning-capable individuals and multiple spawning patterns. This cubera snapper spawning aggregation event probably relates to increased temperatures in the summer months, and the complexity of habitats and geomorphological formations in the region. Even though the species has high economic value in the region, targeted by both commercial and recreational fishing, Brazilian legislation imposes capture restrictions that ignore scientific evidence and are limited to the winter months, a season lacking aggregation reports. Our findings highlight the need for a comprehensive management strategy that includes seasonal fishing closures and monitoring and research collaborative programs.

Large annual variation in the amount of skipped spawning for female Northeast Arctic haddock Melanogrammus aeglefinus

Although the phenomenon of skipped spawning has been described in numerous fishes, time-series are scarce. We used the presence of post-ovulatory follicles in histological gonad slides from females not developing oocytes for Northeast Arctic (NEA) haddock Melanogrammus aeglefinus from 2009 to 2012 to construct a length-based statistical model giving the probability that a non - developing female was skipping spawning, as opposed to not being sexually mature. This model was then applied on demographic winter survey data from the Barents Sea from 1989 to 2014. This indicated large annual variation in skipping numbers. Comparing these survey estimates to the total annual ICES stock numbers, we found that skipping peaked in the years 1994–1996 and 2009–2014, when the median yearly estimate of skipped spawners was 20–45 % of all females aged ≥ 3 years. In contrast, only ∼ 3 % of females at age ≥ 3 years skipped spawning in 2007. The proportional representation of skipped spawners at the stock level appeared linked to stock energy reserves with more skipping occurring when energy levels were low. Skipping also became more frequent with increasing population age, i.e. when immatures were less abundant, although the very largest/oldest fish tended to spawn. Because the proportion of NEA haddock that skips spawning is variable and can be high, understanding variation in this phenomenon and its drivers may improve population dynamic models.

Reproductive biology of the dart squid, Lolliguncula diomedeae (Cephalopoda: Loliginidae) from Gulf of Tehuantepec, Mexico

ABSTRACT Lolliguncula diomedeae is captured incidentally in the by-catch of the shrimp trawl fishery, however, there is little information about its life history. Therefore, data on reproductive indicators were collected in this study to evaluate the reproductive biology of L. diomedeae in the Gulf of Tehuantepec. A total of 1525 specimens, 1354 females with dorsal mantle length (ML) ranging from 18.9 to 90.3 mm and 171 males with 29.2 to 63.1 mm ML. The sex ratio was 8:1 females/males, with two reproductive peaks, one more intense in November and the other moderate in May. The first maturity size (L50) for females was 66.65 and 40.79 mm in males. The histological analysis showed five stages of development: pre-vitellogenesis, vitellogenesis, post-vitellogenesis, spawning, and post-spawning; with the simultaneous presence of oocytes at different stages. In relation to the results found and the consistent presence of post-ovulatory follicles and oocytes of different sizes and developments, we can infer that L. diomedeae is a multiple reproducer, as it spawns in batches in different periods of time in the study area, which can be considered as an adaptation strategy in response to regional environmental changes.

The Reproductive Biology of Female Atlantic Herring in U.S. Waters: Validating Classification Schemes for Assessing the Importance of Spring and Skipped Spawning

AbstractAtlantic Herring Clupea harengus are iteroparous (repeat spawners) with group‐synchronous oocyte development and determinate fecundity, and they are total spawners. However, they also exhibit plasticity in other aspects of their reproductive biology including spawning seasonality and skipped spawning. Previous studies in other regions have reported skipped spawning and errors in macroscopic classifications of maturity, both of which could bias estimates of reproductive potential, but a critical assessment of these in U.S. waters is lacking. In the Gulf of Maine and Georges Bank, herring are assessed as a single stock complex, where females typically mature as 3 to 4 year olds and may live up to 11 years. To evaluate the magnitude of skipped spawning, we collected the ovaries of Atlantic Herring from fishery‐dependent and fishery‐independent sources over multiple seasons and evaluated them histologically to assess imminent (indicated by vitellogenic or maturing oocytes) or recent spawning (evidenced by the presence of postovulatory follicles). Gonad histology allowed us to determine spawning seasonality and skipped spawning. Macroscopic maturity classification was more accurate in fall (1–4% incorrect maturity) than in spring (7% incorrect maturity). The spatial distributions of immature and mature fish from both fishery‐dependent and fishery‐independent sources differed, which affected the estimation of maturity at length and age. We estimated 9–14% spring spawners in the region, but we did not find evidence of skipped spawning. The time series of the macroscopic data that were available (1987–2018) showed increases in spring spawning with latitude, but the proportions have not changed much over recent decades. The effects of up to 30% spring or skipped spawning on a stock assessment of Atlantic Herring were evaluated. Spring spawning had little effect relative to assuming 100% fall spawning (the current assumption), and skipped spawning decreased the scale of spawning stock biomass (SSB) and related reference points, with the degree of change increasing with skipped spawning rates, but it had few consequences otherwise.

Evidence of Iteroparity in Jumbo Squid Dosidicus gigas in the Gulf of California, Mexico

The jumbo squid (Dosidicus gigas) has been considered a species with a semelparous life history, and this assumption has been erroneously adopted without histological evidence. Recent studies suggest that this species can spawn more than once during its life span. To identify the reproductive strategy of jumbo squid, qualitative and quantitative analyses were used in this study. Biological data were collected fortnightly from March 2008 to November 2009 off the coast of Santa Rosalia, Baja California Sur, Mexico. The histological analyses showed five stages of development: previtellogenesis, vitellogenesis, postvitellogenesis, spawning, and postspawning, with the simultaneous presence of oocytes at different substages. These results were confirmed by the presence of multiple cohorts of oocytes at each ovarian stage. Analysis applied to resting females of D. gigas confirmed that the postovulatory follicles were simultaneously found with previtellogenic oocytes denoting the ovarian recovery. The presence of postovulatory follicles at all ovarian stages and in individuals throughout the mantle length (ML) structure (from 32 to 82 cm) was an indicator of multiple spawning events. During 2008 and 2009, four ML groups (41.2, 48.5, 55.2, and 68.5 cm) and threeMLgroups (39.9, 47.8, and 53.9 cm) were observed, respectively. In conclusion, the evidence of postovulatory follicles in resting females of D. gigas indicates that the reproductive strategy of jumbo squid is iteroparity.

Reproductive biology and estimates of length and age at maturity of longtail tuna (Thunnus tonggol) in Australian waters based on histological assessment

The annual global catch of longtail tuna (Thunnus tonggol) has almost tripled in the past 20 years. In the Indian Ocean tuna fishery, longtail tuna catches now exceed those of some principle target species (e.g. bigeye and albacore tuna), resulting in numerous stock assessments concluding the species has been subject to overfishing and overfished for several years. Stock assessment is currently hindered by unreliable biological and catch data, which provided the impetus to study and describe the reproductive dynamics of longtail tuna in Australian waters using histology. Mean (95% confidence interval) length and age at 50% maturity were 535mm (463–570mm) and 2.51 years (2.14–2.79 years). Spawning occurred between October and February, when females produced a mean (±s.d.) of 1516680±743980 oocytes per spawning. Three spawning locations were confirmed based on the presence of postovulatory follicles in a small number of ovaries, although major spawning areas may be located offshore. The present study provides reliable maturity and fecundity ogives that may improve future assessment of longtail tuna stocks throughout the Indo-Pacific region.

Life-history traits of seabream Boops boops (Linnaeus, 1758) in the central eastern Atlantic Ocean (Canary Islands)

Life-history traits of the sparid Boops boops are studied for the first time in an isolated Atlantic population. Boops boops is a hermaphrodite species characterised by late gonochorism or non-functional hermaphroditism. The 1:0.852 ratio of females to males was significantly different from unity. Both sexes had similar size distributions; however, females outnumbered males at sizes of between 16 and 18 cm TL, whereas males predominated among fish larger than 28 cm TL. The average lengths at first maturity for females and males were 16.02 (SD 0.28) and 16.49 (SD 0.25) cm TL, respectively, with no significant difference between sexes. Spawning-capable females were first observed in January, at a low percentage, and were present until May. The gonadosomatic index of both females and males peaked in February. Vitellogenesis did not begin synchronously, and the simultaneous presence of oocytes in all stages of development indicated an asynchronous mode of ovarian development. The presence of postovulatory follicles, together with tertiary-yolk-vesicle oocytes, indicates that the species is a multiple spawner. An age–length key showed an age-group composition for females of between 0 and 4 years, whereas males were between 0 and 5 years. The von Bertalanffy growth parameters for females were L ∞ = 32.3 cm TL, k = 0.44 y–1 and t 0 = −0.81 y, and for males they were L ∞ = 35.3 cm TL, k = 0.38 y–1 and t 0 = −0.80 y.

Assessment of Maturity in the Eastern Gulf of Mexico Florida Stone Crab Menippe mercenaria Fishery

AbstractThe Florida stone crab Menippe mercenaria supports one of Florida's most valuable commercial fisheries. Sustained fishing pressure and overexploitation, despite negative trends in landings, have facilitated the need to transition from stock assessments based on effort and landings toward more sophisticated methods. This requires accurate knowledge of life history parameters, such as size at sexual maturity. The physiological, behavioral, and functional maturity of female Florida stone crabs and the physiological maturity of male crabs were assessed in individuals collected throughout the geographically fished range of the population between 2013 and 2014. Morphological maturity of both sexes was assessed in individuals collected from the same locations in 2005–2016. Histology was used to determine oocyte maturity, presence of spermatophores, and presence of postovulatory follicles in females and the production of spermatophores (present in the anterior vas deferens) in males. Decision tree analysis determined that 50% of females were mature at 43 mm carapace width (CW) based on an indicator of physiological and behavioral sexual maturity. In males, physiological maturity occurred at a CW of 34.75 mm. Sexual maturity estimated using morphological maturity occurred at 66.3 mm CW in females and 63.1 mm CW in males. Differences in estimated size at sexual maturity between morphological maturity and physiological, behavioral, and functional maturity indicate that the relative growth of body parts is not reliable for estimating sexual maturity in Florida stone crabs. Smaller females may be contributing more to the spawning population than had been previously estimated. Large, morphometrically mature males may be more successful in mating encounters, but during times of flux in population size structure (i.e., fewer large males), morphologically immature but physiologically mature males have increased mating opportunities. Results indicate that male and female Florida stone crabs can contribute to the reproductive population multiple times before they become vulnerable to the fishery.

Spatio-temporal dynamics in maturation and spawning of Patagonian toothfish Dissostichus eleginoides on the sub-Antarctic Kerguelen Plateau.

This study investigated maturation and spawning of Patagonian toothfish Dissostichus eleginoides in the Heard Island and McDonald Islands (HIMI) fishery on the Kerguelen Plateau in the Indian Sector of the Southern Ocean based on gonads and otoliths collected between 2004 and 2015 and using histological analyses and calibration of macroscopic staging criteria. Dissostichus eleginoides at HIMI spawn throughout the austral late autumn and winter months of May-August and spawning activity is concentrated on slopes along the west and south of the plateau around HIMI at depths of 1500-1900 m. Comparison between histological analyses and macroscopic gonad staging indicated that many fish that had spawned, as indicated by the presence of post-ovulatory follicles, returned to a resting stage which was macroscopically indistinguishable from maturing fish. Furthermore, the occurrence of females of all size classes with low gonado-somatic index and low macroscopic gonad stage during the spawning season suggested that a proportion of mature females did not spawn every year. Age-at-maturity estimates, based on the assumption that fish of macroscopic stages ≥2 were mature, decreased between the 2004-2009 and 2010-2015 periods for both sexes. The magnitude of this temporal variation in age at maturity, however, varied between gear types and fishing depths and variable sampling regimes probably influenced these variations. This study highlights the importance of correct interpretation of macroscopic gonad stages and understanding the influence of fishery operations on estimations of life-history parameters.

Histological studies of gonads in Neolissochilus hexagonolepis (McClelland, 1839) (Teleostei: Cyprinidae) from Meghalaya, India

Chocolate Mahseer, Neolissochilus hexagonolepis is an important food and game fish of North Eastern region of the country, particularly the high lands of Meghalaya. Reproductive biology of the species has been done under the climatic condition of Meghalaya to understand the gonadal development. The gonadal structure and development stages of germ cells of N. hexagonolepis are described for both sexes. Five stages of development are described based on the histological characteristics of testis and ovary. The kind of development and the presence of postovulatory follicles in ovaries which still contain developing vitellogenic oocytes suggest that N. hexagonolepis spawns over a relatively prolonged period of time.

Assessing oocyte development and maturation in the threatened Delta Smelt, Hypomesus transpacificus

Delta Smelt is a pelagic annual fish species endemic to the San Francisco Estuary, which is protected under U.S. Federal and California State Endangered Acts. In this study we established criteria for scoring Delta Smelt maturity based on the histological features in ovary, as well as measurements of the female sex hormone 17β-estradiol (E2) from liver tissue using radioimmunoassay. We then analyzed the reproductive status of maturing females caught from November 2011 through April 2012 (2011 year-class) by histological examination, E2 quantification, and several common fish metrics including size of oocytes, gonadosomatic index, hepatosomatic index, and condition factor. Histological scoring revealed that Delta Smelt oocytes matured in February through April 2012. The presence of postovulatory follicles with immature oocytes (Stage 1 to 3) further suggests that Delta Smelt are iteroparous, capable of reproducing multiple times during the spawning season. Hepatic E2 concentration was significantly correlated with gonadosomatic index, hepatosomatic index, size of oocytes, and maturation stage. Histological examination of ovaries combined with measures of hepatic E2 and size of oocytes provide a powerful approach to evaluate reproductive performance and maturation timing for the imperiled Delta Smelt.

Age, growth, and reproduction of blackspot snapper Lutjanus fulviflammus (Forsskål 1775) around Yaeyama Islands, southern Japan, between 2010 and 2014

Age, growth, and reproductive characteristics of blackspot snapper Lutjanus fulviflammus around the Yaeyama Islands (24°N, 124°E) in southern Japan were investigated between 2010 and 2014. Samples were caught by angling or purchased monthly at fish markets to cover all size ranges and seasons. Specimens consisted of 280 females (176–347 mm fork length), 177 males (193–325 mm), and 17 juveniles (42–128 mm). Spawning was confirmed from April to August by the presence of postovulatory follicles, which, based on the occurrence of yolked oocytes possibly also occurred in March and September. Maximum fork length and age in the specimens around Yaeyama Islands were 347 mm and 23 years for females and 325 mm and 21 years for males. These results were compared to those reported previously for the species in other regions by standardized criteria. Possible spawning duration of 7 months in the population around Yaeyama Islands is similar to that in New Caledonia (22°S, 5 months) and Okinawa Island (26°N, 6 months), but shorter than that in Tanzania (8°S) and the southern Arabian Gulf (25°N) (~12 months). The maximum body sizes and ages around Yaeyama Islands are also similar to the populations in New Caledonia and Okinawa Island (>300 mm FL, >20 years old), but larger/older than those in Tanzania and the southern Arabian Gulf (<300 mm FL, <20 years old). These differences are thought to reflect water temperature, i.e. spawning duration is shorter in lower temperature regions (annual mean <26°C, New Caledonia, Okinawa Island, Yaeyama Islands) than in higher temperature regions (annual mean >27°C, Tanzania, southern Arabian Gulf). Subsequently, a shorter spawning duration extends the life-span as well as the maximum body size. Longevity of blackspot snapper is thought to be negatively correlated with the duration of the spawning season.

Reproductive strategy of a non-annual rivulid in a perennial wetland

ABSTRACT Atlantirivulus riograndensis (Costa &amp; Lanés, 2009) is a fish registered to the basin of Patos lagoon and the adjacent coastal plains in southern states of Rio Grande do Sul and Santa Catarina, Brazil, found in shallow water courses with that have large quantities of aquatic vegetation and forest edges. The objective of this study was to investigate the reproductive strategy and tactics of this species including the sex ratio, the length at first maturity, spawning type, fecundity and the possible associations among reproduction and abiotic factors. Sampling of specimens occurred in perennial wetlands within the Banhado dos Pachecos wildlife refuge, in the city of Viamão, state of Rio Grande do Sul, Brazil, which is a conservation unit that belongs to an area of environmental protection in the Pampa Biome. The capture of 30 A. riograndensis specimens per month occurred from January to December of 2012. A total of 188 females and 172 males were captured and the total sex ratio was 1:1 in the sampled population. Sexual maturity of the species occurs after 13.59 and 11.92 mm (SL) for females and males, respectively. Both a multiple spawning and a long reproductive period (since August to March) were confirmed by the presence of post-ovulatory follicles that were observed through histological analysis and the values of the gonadosomatic index in females considered spawning capable. The average absolute fecundity of the species is of 19.33 (± 6.18) vitellogenic oocytes in mature ovaries. No significant relationship was found between mean GSI and the abiotic data. Reproductive tactics presented by A. riograndensis indicate a species with an opportunistic reproductive strategy, following the pattern of other species of the Rivulidae family.

Maturity and growth of sablefish, Anoplopoma fimbria, along the U.S. West Coast

Life history parameters such as growth and reproductive processes are dynamic, and shift with environmental and anthropogenic influences. Providing up-to-date life history information is critical for population dynamic models that are used to manage fisheries. Sablefish, Anoplopoma fimbria, are a valuable groundfish species that support commercial fishing throughout the North Pacific Ocean, including off the U.S. West Coast. Ovaries were histologically assessed for maturity status, intensity of atresia, and the presence of post-ovulatory follicles. We evaluated coast-wide length and age at maturity for 477 female sablefish by fitting a logistic regression model to the proportion mature. We also examined length-at-age data for 525 female sablefish based on the von Bertalanffy growth model. Since maturity and growth are important components of models used to assess the status of sablefish, we explored variation in these life history parameters among three regions along the West Coast separated by major biogeographic features at Cape Mendocino, CA (40°26′N) and Pt. Conception, CA (34°27′N). Coast-wide estimates of length (L50) and age (A50) at 50% maturity were 54.64cm and 6.86 years, respectively. Differences in L50 were found north and south of Cape Mendocino, CA, and by depth (range 55–1280m). Length at 50% maturity decreased from north to south and with increasing depth within each region. Age at 50% maturity also differed north and south of Cape Mendocino, CA, with female sablefish maturing at a younger age further north. Growth of female sablefish demonstrated similar differences among geographic areas and by depth. Asymptotic size (L∞, cm) tended to increase at higher latitude and decrease with depth, while growth rates (k, year−1) were elevated north of Point Conception, CA, and generally at depths ≤550m. For female sablefish, the larger size and younger age at 50% maturity, as well as larger asymptotic sizes and somewhat elevated growth rates, were associated with regions within the California Current Ecosystem characterized by elevated productivity and cooler water temperature.

Reproductive biology of the Japanese silver-biddy, Gerres equulus, in western Kyushu, Japan

The Japanese silver-biddy Gerres equulus (Temminck and Schlegel) is one of the most common shore fish in the costal waters of southern Japan and commercially important for the local fishery. In the present study, the reproductive biology of G. equulus is described for the first time and its spawning season and size at sexual maturity were determined. A total of 1081 specimens (484 males and 597 females) were collected in the Yatsushiro Sea, western Kyushu, Japan, from January 2001 to December 2002. Monthly changes in the gonadosomatic index exhibited higher values between June and September, with a peak in July, and the trend was similar for both sexes. Furthermore, the sequential development of the ovaries observed through the histological studies suggested that the spawning season of G. equulus continued from June to September. The female attained sexual maturity at a minimum size of 141 mm standard length. The simultaneous presence of postovulatory follicles and yolk globules in some ovaries indicated that this species is a multiple spawner.

Reproductive biology of the cardinalfish Apogon lineatus in Tokyo Bay, Japan

SUMMARY: Reproductive biology of Apogon lineatus in Tokyo Bay, Japan was studied by histological examination of the gonads and measurement of the gonadosomatic indices (GSI). The spawning season occurred during July–October, with both males and females attaining sexual maturity by the end of their first year (60.0 mm TL). It was indicated that A. lineatus is a multiple spawner by the presence of postovulatory follicles and primary–secondary yolk in the same ovaries during the spawning season and the asynchronism of the development of spermatogenesis. Batch fecundity ranged from 7983 to 19 316 eggs for fish of 76.0 mm TL to 106.0 mm TL, respectively, and increased linearly with fish total length. Increases in oocyte diameter were not observed after the tertiary yolk stage, which suggested an adaptation to mouthbrooding, thereby efficiently utilizing the male's restricted buccal cavity to maximize the number of eggs mouthbrooded.