Prolonged Spawning Research Articles

Size, growth and reproductive biology of the giant mudskipper, Periophthalmodon schlosseri (Pallas, 1770), in Malaysian waters

The size, growth and reproductive biology of the giant mudskipper, Periophthalmodon schlosseri, was studied in the inter-tidal mudflat of a mangrove swamp along a 0.4–0.6 × 5 km stretch of the Sepang coastal waters, Selangor Malaysia. The size ranges of the giant mudskipper specimens caught in the study area were between 10–27.5 cm TL (20.6 ± 3.1 cm) for males and 14.5–28.5 cm TL (21.9 ± 2.3 cm) for females. Male to female sex ratio during the study was 1 : 1.1. The estimated von Bertalanffy growth parameters were L∞ = 29 cm and K = 1.4 year−1, with a growth performance index of Ø′ = 3.1. Otolith microstructure analysis revealed a strong correlation (Female: r = 0.920, n = 35; Male: r = 0.943, n = 41, P < 0.05) between the number of daily rings (number of days old) over the respective size ranges of male (8.5–19.5 cm SL) and female fish (11.8–22.3 cm SL). Four maturity stages were described to follow gonadal development based on external features; these stages were further validated through histological examination of the ovary and oocyte diameter measurements. The gonadal development cycle of P. schlosseri was asynchronous, as marked by the random mixture of early stages oocytes (diameter: 70.7 ± 14.9 μm) to matured stages (356.9 ± 20.2 μm), and had a prolonged spawning season extending from June to October. Monthly fluctuation of the gonadosomatic and hepatosomatic indices for this species was highly correlated (r = 0.126, P < 0.05).

Spawning Season of Argenteus (Euphrasen, 1788)in the Northwest of the Persian Gulf and its Implications for Management

The spawning periodicity of silver pomfret, Pampus argenteus, was investigated in 627 specimens (137 female and 490 male) collected monthly by trawl net from the Northwest the Persian Gulf for a one year period (March 2004 to February 2005). Seven maturity stages were recognized by Kesteven scale. The length at first maturity (LM50) was calculated as 192 mm in combined sex. The overall sex ratio (female: male) was 1:3. Fluctuations in the Gonadosomatic Index (GSI) values and percentage of mature specimens suggested prolonged spawning season from May to October. There were two spawning peaks, the first one between May and July and the second in October. It is concluded that Iranian waters (in Khuzestan province)are the main spawning and nursery grounds for silver pomfret in the Persian Gulf.

Pathogenicity of the protozoan parasite Marteilioides chungmuensis in the Pacific oyster Crassostrea gigas

Marteilioides chungmuensis is an ovarian parasite that causes nodule-like structures to appear on the gonads of female Pacific oysters, Crassostrea gigas. It is known that the prevalence of infection increases in summer and decreases from autumn to spring. To investigate the decrease in prevalence of infection and pathogenicity of the parasite, a biopsy method was developed to detect infected oysters, which were then monitored to calculate the mortality rate. Mortality of infected oysters was recorded monthly and changes in reproductive development observed histologically. Compared with control groups, a significant difference in mortality was observed in infected oysters in September and October. Histological observations showed that infected oysters produced oocytes continuously, even in autumn when healthy oysters were reproductively inactive. This prolonged spawning activity of infected oysters resulted in nutritional wasting and mortality. From December onwards, however, almost all infected oysters survived, though the infection persisted. Infection intensity decreased gradually from December. Histological observations revealed that, in winter, infected oysters released infected and uninfected oocytes through the genital canal. The gonad subsequently degenerated and was replaced with connective tissue, as in normal, healthy spent oysters. The results revealed that prevalence of infection decreased from September to May. It is hypothesised that the decline in prevalence within the epizootic area in autumn occurred because infected oysters died and that the winter decrease was due to recovery from infection.

Reproductive biology of white mullet, Mugil curema (Valenciennes) in the Southern Caribbean

Gonadal development and spawning of white mullet, Mugil curema in the Gulf of Paria, Trinidad, West Indies, was investigated using both macroscopic and histological techniques. M. curema is a multiple batch spawner with a protracted spawning season from November to July. Gonadal development is annual and each female appears to spawn at least twice per year. The prolonged spawning season may thus be an indication of the lack of population synchrony rather than prolonged spawning by a single individual. Peak-spawning activity occurs in June/July and it is hypothesized that it is in response to the start of the rainy season. Oocyte development is group synchronous and development of oocytes in the leading clutch is isochronal.

Reproductive anatomy, gonad development and spawning seasonality of nurseryfish, Kurtus gulliveri (Perciformes:Kurtidae)

The nurseryfish, Kurtus gulliveri, of northern Australia, is remarkable for the fact that the males carry the egg mass on a supraoccipital hook on their forehead. Plankton samples of larval nurseryfish indicate a prolonged spawning season (June–November) that more or less corresponds with the dry season in the Northern Territory. The paired, elongate testes are located in the posterior portion of the body cavity suspended by the mesorchium. The gonadosomatic index (GSI) of males was small and highly variable (mean 0.14, range 0.01–0.27) from June to November. The histological structure of testicular lobes showed maturing and mature stages that contained spermatocytes, spermatids, and spermatozoa. The paired, bean-shaped ovaries contained about 5500 oocytes (1176–9783) and were located in the rear of the abdominal cavity. GSI averaged 1.58 (range 0.36–4.48). Ovarian histology revealed primary growth, cortical alveolar oocytes, vitellogenic oocytes, coalesced yolk, and atresia. The occurrence of postovulatory follicles and late vitellogenetic oocytes in the ovaries clearly indicate that nurseryfish females are batch spawners. Maturing testes showed signs of previous spawnings indicating that males are capable of spawning several times throughout the spawning season. We speculate that nurseryfish may spawn in a manner similar to their closest relatives, cardinalfishes (Apogonidae), with eggs carried on the male’s hook instead of orally.

Some information on the biology of Illex coindetii Verany, 1839 (Cephalopoda, Ommastrephidae) in the South-Western Adriatic Sea (Central Mediterranean)

Distribution, length frequency structure, sex-ratio, maturity and dorsal mantle length–total weight relationship for Illex coindetii (Verany, 1839) were described for the first time in the South-Western Adriatic Sea (Central Mediterranean). Samples came from six experimental bottom trawl surveys carried out within the framework of the Medits programme from 1997 to 2002. Although specimens have been collected at a wide depth range, I. coindetii concentrates between 50 and 200 m. The population had a smaller squid size and length at first maturity with respect to other Mediterranean and Atlantic regions, probably due to the interaction of some environmental factors (sea temperature and fishing pressure) and the biological characteristics of the species. There was no difference in males/females ratio by year, but there was a general dominance of females over males at larger sizes and of males over females at smaller sizes. The different proportion of juveniles and mature individuals in the catch suggested the possibility of a prolonged spawning season with a spring spawning peak. There was a pronounced sexual dimorphism, females mature at larger mantle length attaining larger size in respect of males. Length–weight relationship revealed a difference between sexes in maturing and mature individuals only, with males resulting heavier and more robust than females at the same size. There were no differences in body proportions between unsexed and immature individuals of both sexes, which were considerably slimmer than maturing and mature counterparts.

Effects of exploitation on reproductive capacity of blackspot snapper, Lutjanus fulviflamma (Pisces: Lutjanidae) in Mafia Island, Tanzania

AbstractThere is paucity of information on the effects of exploitation on reproductive characteristics of blackspot snapper, Lutjanus fulviflamma (Forsskål 1775) in Tanzanian coastal waters. We compared size at first sexual maturity (LM50), sex ratio, fecundity, and breeding season of L. fulviflamma in least fished Mafia Island Marine Park (MIMP) and intensively fished areas (IFA) between May 1999 and April 2001. Fish in MIMP matured at significantly smaller size (female: LM50 = 206.3 mm; male: LM50 = 195.5 mm) than in IFA (female: LM50 = 216.7 mm; male: LM50 =212.1 mm) total body length. Sex ratio was balanced at 1.03 : 1 (female : male) in MIMP, but it was skewed 0.9 : 1 (female : male) in IFA. Size‐related differences in sex ratio were observed with males predominating in the smaller sizes and females in the larger sizes. Total fecundity of fish in MIMP was determined at 45,200–430,200 oocytes in females of between 207 and 293 mm total length. Lutjanus fulviflamma in MIMP has a prolonged spawning season lasting from September to March peaking in December. None of the fish from IFA were in breeding state, suggesting recruitment overfishing is an added matter of concern for the long‐term sustainability of the fishery at the current exploitation level.

Comparison of lake sturgeon (Acipenser fulvescens), Stizostedion spp., Catostomus spp., Moxostoma spp., quillback (Carpiodes cyprinus), and mooneye (Hiodon tergisus) larval drift in Des Prairies River, Quebec

Several fish species that spawn in lotic habitats have a larval-drift phase which is a major determinant of their reproductive success. The main objective of this study was to compare seasonal, diel, longitudinal, transverse, and vertical variations in rates of lake sturgeon (Acipenser fulvescens), Stizostedion spp., Catostomus spp., Moxostoma spp., quillback (Carpiodes cyprinus), and mooneye (Hiodon tergisus) larval drift in Des Prairies River (DPR) near Montreal (Quebec), which is one of the major lotic spawning habitats of the St. Lawrence River system. Larval sampling was conducted in the spring of 1994 and 1995 for the six taxa, and on a more restricted basis for lake sturgeon in 1996–1998, using drift nets set at several transects, stations, depths, and periods of the day, along a 19 km long section of river beginning ca. 2 km downstream from the DPR power house. For all taxa except lake sturgeon, peak larval drift occurred ca. 1 week earlier in 1995 than in 1994. The sequence was very similar between years, beginning with Stizostedion spp., followed by Catostomus spp., then lake sturgeon, quillback, and mooneye drifting simultaneously, and finally Moxostoma spp. Generally, for all taxa except quillback, whose multimodal drift pattern suggests intermittent, prolonged spawning, larval-drift profiles showed one major seasonal mode, which was observed simultaneously at all transects. For all taxa except quillback, drift rates peaked between 21:00 and 03:00 and were minimal during daylight hours. Lake sturgeon and Stizostedion spp. larval drift rates decreased radically from the most upstream to the most downstream transect, suggesting that both taxa spawn mostly in the vicinity of the DPR power house. More studies are required to explain this longitudinal decline in drift rates, particularly for lake sturgeon. The other taxa showed longitudinal variation in larval drift rates, suggesting that they spawn near the DPR power house and (or) in the Île de Pierre Rapids, ca. 12 km downstream. At all transects, larval drift rates for the six taxa were generally higher in the right half (Montreal) of the river, suggesting that eggs are deposited mostly in this part of the river at the two major spawning areas and that larvae tend to remain in the same general corridors during downstream migration. For all taxa, though to a lesser extent for lake sturgeon, nocturnal drift rates tend to be higher near the surface than at mid-depth and near the bottom, the reverse situation being observed for diurnal drift rates.

Multiple Induced Spawnings of the Indian Catfish Heteropneustes fossilis (Bloch) within a Prolonged Spawning Season

Abstract Singhi, the Indian catfish Heteropneustes fossilis, attained gonadal maturity repeatedly in a single spawning cycle by photothermal treatment. After the first spawning, maintenance at 30 C and 14 h light/10 h dark for 3 wk induced recruitment of the next batch of mature oocytes for subsequent spawnings. The number of eggs released declined with each spawning. However, fertilizability of the eggs was maintained until the fifth spawning. Mature fish were induced to spawn by D‐Lys6 salmon gonadotropin‐releasing hormone agonist administration. The dose of salmon gonadotropin‐releasing hormone agonist for the second and subsequent spawnings was determined to be 25‐fold less compared to the dose administered for the first spawning. Fish released the maximum number of eggs upon induction when they were maintained continuously at 30 C and 14 h light/10 h dark for 6 wk. The result obtained in the present study points to a possibility of obtaining multiple spawnings from those species of farmed fish which spawn once a year.

Reproduction of river and lake populations of Hyridella depressa (Unionacea: Hyriidae) in New South Wales: implications for their conservation

The freshwater mussel Hyridella depressa is an important component of the macrobiota of freshwater systems of south-eastern Australia. This species has declined in river habitats but is abundant in impounded water storages. Reproduction of river and lake populations of H. depressa was investigated to document details of their gametogenic cycle and to determine when the females incubate embryos in their gill marsupia. Four populations in Lake Burragorang and two populations in the Hawkesbury-Nepean River were studied over two breeding seasons. Reproduction was documented by anatomical and histological examination of the gonads. The study sites differed in anthropogenic influence and trophic status and the influence of these factors on reproduction in H. depressa was assessed. A skewed sex ratio in favour of females was common in the populations and histology revealed that some of these females were microhermaphrodites. It appears that sexuality in H. depressa is labile with the potential for self-fertilisation by individuals that largely function as females. H. depressa is a long-term brooder with progeny present in the marsupia for up to eight months of the year from mid-winter to late summer. Across all sites brooding started in July or August and finished in January or February of the following year. In parallel with the prolonged spawning pattern, gametogenesis in H. depressa was continuous. At the eutrophic sites the gonads contained advanced gametes throughout the year. H. depressa at these sites had a high annual reproductive output with the females producing several clutches each year. In contrast, gametogenesis in mussels at the oligotrophic sites was more seasonal. At one of the oligotrophic sites reproductive failure was common and in 1996 most females failed to brood a single clutch. Implications of this research for conservation of H. depressa are discussed.

Pheromone-Induced Spawning of Pacific Herring

A spawning pheromone in the milt (semen) and testes of the Pacific herring,Clupea harengus pallasi, triggers spawning in sexually mature fish of both sexes and is thought to facilitate school spawning of this species. We found the response to the pheromone to be a stereotyped behavioral sequence consisting of a graded extension of the gonadal papilla, release of gametes, and spawn deposition behavior. The response is triggered by an olfactory stimulus, as demonstrated by the elimination of the response by occlusion of the nares. Stimulus concentrations of an approximate 1:500 dilution of fresh milt or the equivalent of 0.02 g of fully mature testes per milliliter were required to elicit a response in 50% of ripe herring that are responsive to the pheromone. Female fish appeared to be less sensitive to the pheromone in milt than males early in the spawning season, but not thereafter. The average duration of responses of male fish was longer after exposure to concentrated milt than to testes extracts, but no consistent difference in response times of the two sexes was detected. Factors other than the spawning pheromone, maturity of the fish, and stress also were found to influence the spawning response. For example, exposure to shallow (3 cm) water in a small tank induced “spontaneous” papilla extension and spawning approximately 20 min after refilling the tank; occluding the nares prevented this response. Also, the presence of floating kelp (Macrocystis) resulted in prolonged spawning in a large tank after pheromonal stimulation.

Fecundidad y épocas de reproducción del "pargo mancha" Lutjanus guttatus (Pisces: Lutjanidae) en el Golfo de Nicoya, Costa Rica

The reproduclive cyc1e of the spotted snapper Lutjanus guttatus was studied from January 1993 10 Januar 1994 al the Gulf of Nicoya. Costa Rica. The occurrene of mature fish over a prolonged period and high gonado somalic and condition indexes during a number of months lend additional evidence for a prolonged spawning season of Ihe lish. Size at first maturity was estimated a 32.0-32.9 cm total body length or TL (male) and 33.0-33.9 cm TL (female. Fecundity ranged from 1 363 000 (56.9 cm TL) to 60 454 (31.9 cm TL) eggs. Gonads analysis showed asynchronical development of the oocites with intermittent spawns.

Spatial and temporal distribution and recruitment of echinoderm larvae in the Ligurian Sea

Seasonal and annual variations in the distribution and abundance of echinoderm larvae (early to post-larvae of principally echinoids and ophiuroids), were determined from a series of plankton net tows taken at three stations in the Bay of Villefranche (France) and along a radial transect of 28 nautical miles (52 km), from the Bay to half-way to Corsica, between 1984 and 1988. Spatial distribution of six echinoderm species have been mapped. For the echinoids, Paracentrotus lividus and Arbacia lixula, spawning takes place twice a year and appears to be synchronous because larval cohorts were comprised of distinct age-classes both near and far from the coast. Recruitment for these species is, therefore, thought to occur at well-defined periods. In contrast, the ophiuroid species studied (Amphiura filiformis, Ophwthrix fragilis, Ophiopluteus bimaculatus and O. compressus) spawn several times per year with a relatively short period in late spring and a prolonged spawning between the end of autumn and winter. These later results are consistent with the presence of mixed size-classes of larvae either from the nearby coast or offshore. Recruitment for these ophiuroids appears to be much more variable and spread over time.

Seasonality and spatial variability in the reproduction of two Antarctic holothurians (Echinodermata)

Seasonality in the reproduction of Ekmocucumis steineni and Psolus dubiosus (Holothuroidea) from the Antarctic shelf was investigated. The material was collected in spring (October/November) and autumn (mainly February) in the southeastern Weddell Sea. For E. steineni differences between both seasons in relative female fecundity and relative gonad weight were found in both sexes. Large yolky oocytes (0.3–1.0 mm in diameter) forming 1–3 cohorts were present in spring, nearly none in autumn. A delayed or prolonged spawning is possible, depending on the locality. No seasonal differences were found in P. dubiosus, a brood-protecting species with a lower fecundity and larger eggs (≤1.5 mm in diameter). A longer spawning phase in P. dubiosus than in E. steineni (October to January) is suggested. Both species are suspension feeders and their intestines were more filled with organic material in autumn than in spring. However, the occurrence of mature oocytes was not directly linked with the seasonal availability of food. The size-frequency distribution of the entire material in the study area was heterogeneous, indicating differences in long-term environmental conditions. The data show an evolutionarily more evolved high Antarctic mode of reproduction in P. dubiosus with a prolonged reproductive period than in E. steineni which has a distinct annual spawning cycle.

Reproductive biology and spawning of the myctophidLampanyctodes hectorisand the sternoptychidMaurolicus muelleriin the southern Benguela Ecosystem

The myctophid Lampanyctodes hectoris is caught by purse-seiners in the Benguela ecosystem off southern Africa. Ichthyoplankton surveys indicate peak spawning in late winter/spring, with eggs and larvae concentrated offshore of the 200 m isobath. Fecundity ranges from 572 to 1431 eggs·g−1 wet body mass, and gonadal activity is confined to a few months of the year, peaking in July and August. The sternoptychid Maurolicus muelleri is not fished commercially in the Benguela ecosystem, but its eggs and larvae are present throughout the year, with a maximum in summer and a lesser peak in winter. Maximum egg abundance follows the 200 m isobath in water of surface temperature 12,75–15,45°C. Its fecundity ranges from 161 to 738 eggs·g−1 and gonads are active during all months, suggesting a more prolonged spawning season than for L. hectoris.

Reproduction of the North American blackbass, Micropterus salmoides (Lacepède), in an equatorial lake, Lake Naivasha, Kenya

Abstract. In contrast to its North American relatives, the Lake Naivasha blackbass, Micropterus saimoides (Lacepdde) has a prolonged spawning season of 8 months between June and January, peaking in August to November. This season is characterized by the presence of high numbers of mature fish with the highest gonadosomatic index (GSI). Analysis of GSI variations in different length-classes reveals that maximum reproduction occurs in the 30-34.9-cm length-class in males and 40-44.9-cm in females. Analysis of the GSI values in the different sampling stations identifies two stations as the breeding areas of M. salmoides in the lake. The positive correlation between the GSI and the stomach fullness index suggests that the species probably feeds all year round, including the spawning season. Fifty per cent of males and females are mature at 25-29.9-cm and 30-34.9-cm length-classes respectively. The fecundity of fish of 28.4 cm (371 g) to 33 cm (550g) ranged from 1300 to 3524 with a mean of 2203 eggs. Fecundity had no relationship with body length but increased linearly with body weight.

Diet, Growth, and Potential Competitive Interactions between Age-0 White Perch and Yellow Perch in Oneida Lake, New York

Abstract Diet and growth of age-0 white perch Morone americana and age-0 yellow perch Perca flavescens were compared during July–October 1980 and 1987. Both fish species fed on Daphnia pulex in 1980 and growth was rapid; prey biomass per gram of fish was 2–12 times higher for white perch than for yellow perch. In 1987, white perch consumed up to three times more prey biomass than yellow perch, but the subsequent disappearance of D. pulex caused both fish species to switch to macroinvertebrates and growth of both species declined. Between 1977 and 1987, mean weights and specific growth rates of white perch exceeded yellow perch by October in all years, and weights of white perch were closely tied to the density of D. pulex in late summer–early fall (Spearman's rank correlation = 0.58, P = 0.07). Diet overlap for age-0 white and yellow perch was high when D. pulex was present, and the potential for interspecific competition was greatest when these fish were similar in length. Because of a prolonged spawning...

Comparative study of sexual cycles, oogenesis and spawning of two Soleidae, Solea lascaris (Risso, 1810) and Solea impar (Bennet, 1831), on the western coast of Brittany

Two sand sole species, Solea lascaris and Solea impar, are common on the western coast of Brittany, France. Their reproduction (oogenesis and spawning) has been studied by following the gonadosomatic index, histological changes in ovary development, and oocyte diameter distribution. Both species have a prolonged spawning season, from spring to late summer. Each mature female breeds twice during the spawning season: in May and July for 5. lascaris, and in early June and July for 5. impar. Throughout the spawning season, several oocyte batches undergo vitellogenesis and there is a continuous recruitment of immature or primary oocytes into vitellogenesis. The two species are thus serial synchronous spawners. This, together with oocyte atresia late in the season (especially noticeable in S. impar) makes fecundity estimation difficult.

Egg production of the Arctic copepod Calanus glacialis: laboratory experiments

Egg production of single female Calanus glacialis Jaschnov fed with Thalassiosira antarctica at super-abundant concentrations (>300 μg C l-1) was determined over several weeks. Experiments were performed directly after collection from the East Greeland Current in June 1987 and 1988, and during resumed feeding after long-term starvation over 4 (October 1988), 4.5 (October 1987) and 6.5 (January 1988) mo. In addition, in June 1987, short-term starvation experiments of 5 and 15 d were conducted. Egg production was closely related to feeding in all experiments. While directly after collection eggs were produced within a few days, it took 2 wk (October 1987 and 1988) and 10 d (January 1988), respectively, to resume egg production after long-term starvation. During long-term starvation periods eggs were not laid. The decrease in total egg production with duration of starvation was due to decreasing clutch size and increasing spawning interval. In contrast, short-term starvation experiments only affected spawning interval. Interannual variability in egg production was high, with much higher clutch sizes in 1988. Average production rates in June 1988 correponded to 5% body C female-1 d-1, the maximum was 7.4% (1 274 eggs in 23 d). Carbon content of eggs was 0.40 μg egg-1. C. glacialis is well adapted to pulsed food events in the Arctic by its longevity; its ability to preserve its reproductive potential over several months; its rapid mobilization of ovaries; and by its high egg production rates. The implication of prolonged spawning capacity on life cycle studies is discussed.

Life cycle, growth and production in estuarine populations of the polychaetes Nereis virens and N. diversicolor

Life cycle, growth, mortality and production of the polychaetes Nereis virens and N. diversicolor were studied in Norsminde Fjord, Denmark. When 3 yr old, N. virens showed synchronous spawning induced at new moon in April when water temperature was 10–12°C. Nereis diversicolor showed a prolonged spawning during early spring and summer at an age of 12–18 months. Average weight‐specific growth rate for N. virens and N. diversicolor were O.0062 and 0.0050 d−1, respectively; showing a reduced rate with age. Annual mortalities of 76–77% and 98%, respectively, reduced N. virens to 1.2–1.4% and N. diversicolor to 1.2–2.3% of the initial population at the time of spawning. Annual production of N. virens and N. diversicolor was 23.73 and 27.17 g AFDW m−2, tantamount to an annual turnover (P/B) of 2.52 and 2.60, respectively.