Reproductive condition of the pearl oyster, Pinctada imbricata, Roding, in Port Stephens, New South Wales, Australia

In an investigation of the potential for pearl production in New South Wales (NSW), Australia, changes in the physical and reproductive condition of the pearl oyster, Pinctada imbricata, were monitored for over 2 years. Using wild oysters gathered from close to the southern extent of the species' range in Port Stephens, NSW, a series of macroscopic and histological observations were made. Reproductive activity in P. imbricata was greatest from late spring to early autumn with oysters in poor reproductive condition during winter. Peaks in reproductive indices occurred in November 1998, March 1999, December 1999 and April 2000. Four indices of physiological condition were used: shell growth, byssal attachment, mantle thickness and mucoprotien layer. With the exception of the thickness and extent of the mucoprotein layer, these indices either showed little variation or the variation that occurred was not related to seasonal or reproductive changes. Changes in the mucoprotein layer were correlated with water temperature and suggest that this layer is metabolized during periods of high demand such as during gonadogenesis. Collectors deployed at two sites in Port Stephens demonstrated that spatfall occurs largely in the months of December and January following the spring and early summer peaks in reproductive activity (November 1998 and December 1999). Spatfall was not observed following the autumnal peaks (March 1999 and April 2000) in reproductive activity. Overall, reproductive patterns in P. imbricata are poorly suited to spat supply in Port Stephens. Farmers require spat in early spring (September) to allow maximum use of the ‘growing’ season (September–May). Reproductively capable oysters are not available from the wild until September and quantity of natural spatfall is too variable and occurs too late in the season (December–January). As a result, oysters are being conditioned in the hatchery in July, spawned in August and spat are supplied to farmers in mid September.

Latitudinal variation in reproductive behavior in the pearl oyster, Pinctada albina sugillata

The annual mass spawning of scleractinian corals on the Great Barrier Reef (GBR), Australia, is purported to be unprecedented in terms of the taxonomic and geographical scale of spawning synchrony. Here, we compare spawning synchrony both within and among coral species in four regions spanning 10°of latitude on the GBR and compare this with four regions separated by a similar latitudinal range within the Japanese tropical and sub-tropical Archipelago. On the GBR, peak reproductive activity at all latitudes occurred in November whereas there was a clear disjunction in the period of peak reproductive activity among the four regions in Japan, with tropical locations spawning up to 3 months earlier. In Sekesei Lagoon (22°N), a high proportion of Acropora colonies were mature following the full moon in April; at Akajima Island (26°N) peak reproductive activity occurred in May; at Oku (28°N) peak reproductive activity occurred in June and in Amakusa (31°N), reproductive activity likely peaked in July. However, mature colonies of Acropora were found prior to every full moon for at least 5 months at two regions examined in detail (The Whitsundays Islands on the GBR and Akajima Island). While these regions on GBR appear to act more homogeneously than regions over a similar latitudinal range in Japan with respect to the timing of peak reproductive activity, and the proportion of colonies mature was often higher during these peaks, the reproductive season on the GBR is much longer (5 months) than is typically appreciated.

Reports of seasonal patterns in reproduction are uncommon for Amazonian upland‐stream shrimps (Caridea: Palaemonidae), since changes provoked by heavy rainfall in these systems are not as marked as in large rivers. Differences in the proportion of ovigerous females throughout the year are subtle and seem to be more a result of responses to environmental variation than interspecific competition. Despite these shrimp species reproducing continuously throughout the year, peaks of reproductive activity are believed to occur during the rainy season, as in large rivers, since changes in main‐channel hydraulics favour dispersion and habitat/food availability. Seasonal size variation due to variation in reproduction or mortality can also occur throughout the year, and recruitment is frequent during ebb and drought. Therefore, if any temporal pattern exists, reproductive activity is expected to be related to seasonal changes in precipitation and stream hydraulic features. To address these questions, we investigated whether upland stream shrimps show temporal patterns of size variation and reproduction (based on the proportion of ovigerous females) and whether precipitation and stream hydraulic features are correlated with the proportion of ovigerous females. We detected minimal mean‐size variation throughout the months for all species; thus, size changes do not follow a temporal pattern in our time series. A non‐random temporal pattern in the proportion of ovigerous females was found only for Pseudopalaemon amazonensis, but none of the measured predictors was related to this proportion. Despite the lack of a consistent temporal effect, the number of ovigerous Macrobrachium inpa showed a significant positive relationship with stream flow. Our findings confirm that Amazonian upland‐stream shrimp species reproduce continuously throughout the year, but non‐random temporal patterns of reproduction occur in some species. Size variation did not show any temporal pattern in our time series. Stream flow was found to be positively related to reproduction in one species. These results add evidence to shrimp reproductive ecology research on how local changes in stream velocity can affect shrimp species reproduction. Moreover, further investigation is still needed to predict future effects of water level variation on shrimp species traits as climate change advances.

Reproductive biology of the horned viper, Cerastes cerastes gasperettii in the central region of Saudi Arabia

The cichlid fish T. leucosticta (Trewavas) was studied by fortnightly seining an area of an equatorial lake (Lake Naivasha) in Kenya to study their reproductive and gonadal patterns. The study lasted 16 months during which period temperature, rainfall and (for the last 11 months) sunlight patterns were obtained and analysed. Testicular and ovarian development was lowest in the months of July‐August. No evidence of breeding was detected during this period. This period is also marked by the lowest rainfall, the lowest temperatures and least sunlight. Slight but fluctuating breeding activity and gonadal development is resumed in October following increased sunlight and temperatures from September. The period December to February is marked by sustained high temperatures, high sustained maximal sunlight and low rainfall. It is also the period of rising gonadal development in most mature males and females reaching a peak in both sexes in February. This is followed shortly after by a sharp peak in reproductive activity. It is concluded that sunlight and temperature are the most important factors influencing gonadal development and subsequent breeding in Tilapia even under equatorial conditions. When preceded by conditions of sustained high temperatures and good sunlight which are conducive to the maximal development of the gonads of both sexes, the onset of rainfall seems to stimulate the initiation of the peak breeding activity. Sustained heavy rainfall on the other hand seems to check breeding.

We examine seasonal and interpopulational variation in field levels of corticosterone (B) in the lizard Uta stansburiana. Corticosterone is the primary reptilian glucocorticosteroid, and elevated levels of this hormone have been correlated with physiological stress under both field and laboratory conditions. Patterns of seasonal variation in plasma B were generally similar in males and females, with peaks coinciding with periods of peak reproductive activity (males) or peak reproductive condition (females). Levels of circulating B usually declined as the activity season progressed and were lowest in late summer, especially among males at desert sites-including our southernmost site, where lizards exhibited poor body condition as a result of drought. Variation in B levels among populations was probably attributable to variation in the timing of seasonal samples (e.g., in relation to peaks in reproductive activity). Apparently, these populations did not experience serious (i.e., debilitating) physiological stress, as the highest recorded levels were lower than those of captive-stressed U. stansburiana. This suggests that corticosterone levels simply parallel annual patterns of activity, especially reproduction. These findings agree with other studies that have indicated a positive, rather than a negative, association between glucocorticosteroid secretion and reproductive activity. These results also suggest that basal (baseline) levels of B in free-living animals may not be indicative of the degree of "stress."

Numerous factors are hypothesised to limit the geographical distribution of reef organisms, such as corals. For example, high-latitude populations of some marine invertebrates are not reproductive, rather they are sustained by the input of larvae from reefs closer to the tropics. Here, we investigate the reproductive biology of high-latitude corals in Moreton Bay, Australia, to test whether or not these populations have the capacity to be self-sustaining. The reproductive condition of 21 scleractinian species was determined in November and December 2002 and 2003 and January 2004. Seventy percent of colonies (n = 97) were gravid and at least one gravid colony was found in 86% of the species, suggesting that reproductive activity is concentrated in late spring and summer. Mature colonies were present in all three months and immature colonies were present in January, indicating a reproductive season of at least four months. The proportion of mature colonies was highest in January (42%) suggesting a peak in reproductive activity at this time. Coral populations of Moreton Bay clearly have the potential to be self-sustaining; however, their isolation from other reef areas suggests that these populations may be slow to recover from disturbance.

The freshwater threespine stickleback (Gasterosteus aculeatus) shows tremendous interpopulation variation in a variety of phenotypic traits, including reproductive characteristics. We investigated individual-level reproductive patterns in the freshwater Ono population in Japan, which occurs nearly at the southern global range limit for this species. Although G. aculeatus populations generally only reproduce in spring and/or summer, we directly observed tagged individuals in semi-natural enclosures and found that both males and females reproduced almost the year long. We observed two peaks in reproductive activity, spring to early summer and autumn to early winter, at both the population and individual levels. Thus, we found unique features in the timing and duration of reproduction of this freshwater population, which inhabits spring-fed areas with constant year-round water temperatures.

Describing the natural history of endemic and endangered species is useful for developing effective conservation plans. Two important pieces of natural history are the timing of reproduction and morphometrics. In this study, we estimate the reproductive season of Antioquia Brushfinch (Atlapetes blancae) based on a large database of observations and captures. We also provide the most extensive morphometric database of males, females, and juvenile individuals for this species. Taking advantage of ecological modeling techniques, we estimated that the reproductive season of A. blancae most likely spans from February through August with peak reproductive activity during May. The reproductive activity is highly correlated to day length (r=0.68 95% CI = 0.2 – 0.9; t=2.9, df=10, p = 0.01) and precipitation during the first rainy season of the year (r= 0.88 95% CI = 0.3 – 1; t=3.9, df=4, p=0.02). Furthermore, it is also highly correlated with the reproductive activity of many other species in the genus Atlapetes (r=0.81 95% CI = 0.4 – 0.9; t=4.4, df=10, p = 0.001). We also found that juveniles are smaller than adults and females are smaller than males providing evidence for both, age and sex size dimorphism. This study is the first attempt to provide important missing information about A. blancae that could help with understanding population viability. With this study, we now can focus conservation actions on periods of reproduction which are important bottlenecks of bird populations.

The reproductive ecology of Pavona gigantea Verrill and Gardineroseris planulata (Dana) was investigated in the equatorial eastern Pacific region from 1985 to 1994. These zooxanthellate scleractinian corals were adversely affected in this region during the 1982–1983 El Nino warming event. Both species were hermaphroditic, with individual colonies showing sequential cosexual development, thus resulting in dominantly outbreeding reproduction. Sexuality was mixed, with high percentages of gonochoric and hermaphroditic colonies in both species. Approximately 1:1 male-to-female gonad ratios were found in gonochoric and hermaphroditic colonies combined. Broadcast spawning was observed in P. gigantea in the Galapagos Islands, and the sudden disappearance of mature gametes and the presence of spent gonads suggest that G. planulata is also a broadcast spawner. Colonies of both species with ≲200 cm2 (10 cm diam) live tissue were nonreproductive. Estimated ages of the youngest reproductive colonies were 11 yr for P. gigantea and 20 yr for G. planulata. The percentage of all colonies of P. gigantea with gonads at nonupwelling sites (Cano Istand, Costa Rica and Uva Island, Panama) ranged from 37 to 47%, respectively; colonies with gonads from upwelling environments (Saboga and Taboga Islands, Panama) ranged from 31 to 39%, respectively, and reproductively active colonies from the thermally variable Galapagos islands comprised 40% of the collections. Compared with P. gigantea, the numbers of sexually active G. planulata colonies were roughly onehalf at nonupwelling Cano Island (20%) and Uva Island (25%) sites, or less (10%) at the upwelling Saboga Island site. Peak reproductive activity in P. gigantea occurred during the rainy season at all study sites. In the nonupwelling Costa Rican (Cano Island) and Panamainan (Uva Island) sites, mean monthly sea-surface temperatures (SSTs) were high (28 to 29°C), but slightly lower than in the dry season (29°C). In the upwelling Gulf of Panama (Saboga and Taboga Islands), reproduction occurred after mean monthly SSTs increased from 24 to 28–29°C. In the Galapagos Islands, reproductive activity peaked during sea warming, when mean monthly SSTs reached 25°C. Sexually active colonies of G. planulata, present only at the main collection sites of Cano and Uva Islands, were also observed during the wet season. The presence of mature or spawned gonalds in both species mostly around new and full lunar phases suggests that spawning is at least weakly synchronized with moon phase. Fecundity estimates disclosed the following nonsignificant differences between sites for P. gigantea, expressed as egg production cm-2 colony surface surface yr-1: Galapagos (10 300 to 30 800), Uva Island (4900 to 9800), Cano Island (1800 to 7400), Saboga Island (600 to 1300) Taboga Island (1200 to 2400). Fecundity estimates for G. planulata were considerably lower: Uva Island (700 to 1400), Cano Island (500 to 1000). The sexual recruitment of P. gigantea into El Nino-Southern Oscillation (ENSO) 1982–1983-disturbed, equatorial eastern Pacific coral communities has been low, with only moderate recovery evident since 1983. G. planulata has revealed no sexual recruitment where seed populations are absent or rare (Cano Island, Galapagos Islands), and only low recruitment (Panama) in areas with colonies that survived the ENSO disturbance.

Population biology and assessment of the orange-spotted grouper, Epinephelus coioides (Hamilton, 1822), in the southern Arabian Gulf

Abstract– Stock dynamics of the introduced tilapia Oreochromis mossambicus and co‐occurring indigenous cyprinids were studied in a typical lowland reservoir in Sri Lanka. All species exhibited peaks in reproductive activity during the rainy seasons in November and May. O. mossambicus was estimated to grow to 14 cm in its first year and to 21 cm in its second. A high natural mortality (M was found, both for the cyprinids (M=1.3 yr−1 to 4.7 yr−1 over a range of species) and for O. mossambicus (M= 1.9 yr−l and 1.7 yr−1 for females and males). The fishing mortality (F) of O. mossumbicus, estimated for the length range from 15.0 to 18.5 cm, was 5.5 yr−1 for females and 4.7 yr−1 for males. The total fish biomass was estimated at 1 829 kg/ha, with 128 kg/ha O. mossambicus and 1 098 kg/ha small pelagic cyprinids, mainly Amblypharyngodon melettinus. The total biological fish production was around 5 400 kg/ha/yr, with O. mossambicus and the small pelagic cyprinids accounting for 400 kg/ha/yr and 3 600 kg/ha/yr respectively. The commercial fishery yielded 242 kg/ha/yr (including 70% or 169 kg/ha/yr O. mossambicus), indicating an incomplete utilization of the total biological fish production. It was concluded that there is scope for an approximately 100% increase of the total yield. Reimplementation of a 76 mm minimum mesh size, to prevent overfishing of O. mossambicus, is recommended as a management measure. Additional options are direct exploitation of the untapped resource of small pelagic cyprinids, or indirect exploitation by means of a culture‐based fishery on Lates calcarifer, a controllable predator.

-We described the reproductive biology and population structure of the plains minnow (Hybognathus placitus) during 2 yr in the Cimarron River, Oklahoma. Monthly changes in gonadal weights and mean ovum diameters revealed that the spawning season of H. placitus was prolonged, beginning in spring and ending in late summer. Two peaks in reproductive activity, one in May and the second during midsummer, occurred both years. Spawning in both years coincided with high or receding flows. Most male and female H. placitus began to mature sexually at 45-50 mm SL. The sex ratio did not differ meaningfully from 1:1; males and females were similarly sized. Numbers of mature ova were correlated with standard length and weight ranging from 417 to 4134 for females 51 to 87 mm SL. Length-frequency distributions revealed that H. placitus was short-lived, with most individuals reproducing and dying in their second summer.

The reproduction of three species of mud snails, Hydrobia neglecta, H. ulvae and H. ventrosa is studied under constant conditions of various temperature/salinity combinations and in seven field populations. Under otherwise constant conditions the egg production of H. neglecta increases with temperature (4-24°C), while it decreases in H. ulvae and H. ventrosa. All species show a general peak in reproductive activity around 20 ‰ salinity. In H. neglecta egg production is retarded at low salinity, which may explain the absence of the species in the inner Baltic Sea. All natural populations exhibit peak reproductive activity during May-June, and total numbers of eggs compare well with the values obtained under constant conditions.