Lek-like spawning,parental care and mating periodicity of the triggerfishPseudobalistes flavimarginatus (Balistidae)

Synopsis The triggerfishPseudobalistes flavimarginatus has a lek-like spawning system at Yonge Reef, Great Barrier Reef. Males migrate to a traditional mating ground where they establish territories enclosing nest sites and egg chambers. Females arrive several days later and choose a male for mating. There is biparental care of the fertilized eggs and a strict division of labour. Females appeared to be confined to the nest site by the male. Mating was semi-lunar: eggs were observed in nests several days before the new and full moons on days when high tide occurred near sunset. Differences were observed in the spawning system of another triggerfish (P. fuscus) between the Great Barrier Reef and the Red Sea. Observations of another triggerfish (Balistoides viridescens) are also reported.     

The Role of Temperature and Embryo Development Time in the Diel Timing of Spawning in a Coral-reef Damselfish with High-frequency Spawning Synchrony

We studied the diel timing of spawning in the demersally spawning Hawaiian damselfish, Dascyllus albisella, from mid-June to late-September 1997 at two small patch reefs in Hawaii. Our objectives were to elucidate daily timing of spawning in relation to water temperature, diel timing of hatching, and short-period spawning synchrony. Spawning occurred every 5–7 days at both reefs, with all spawning on a reef concluded either within a single day (1-day spawning) or within two successive days (2-day spawning). Spawning began in early morning and continued for most of the day. There was a significant, positive linear relationship between mean daily average water temperature (= daily average temperature averaged over the period starting from the day following the last spawning day of the preceding nest cycle till the day before the first spawning day of the current cycle) and peak spawning hour of day, for 1-day spawning, and the first and second days of 2-day spawning at both reefs. The relationship between mean daily average water temperature and peak spawning hour of day was comparable among all spawning-day classes and reefs. Hatching occurred on the fourth day of development throughout the study despite the 26.5–29.1°C change in water temperature during the study period, and hatching was restricted to within two hours after sunset. We propose that D. albisella's peak spawning time is positively correlated with increased water temperature because it maintains the benefits of synchronous spawning within two constraints: the narrow daily period of hatching, and the inverse relationship between water temperature and embryo developmental time.     

The reproductive biology of an armoured catfish,Loricaria uracantha,from Central America

Synopsis The reproductive biology of one of the poorly known armoured catfishes, Loricaria uracantha, was studied in Panama. Natural nesting sites consisted of cavities in pieces of wood, open at both ends and positioned above the stream bottom, but artificial cavities of PVC pipe were readily used. Males possess bony bristles on the head and pectoral fins which contact the female prior to oviposition. Males spawned with up to five females in short succession and remained with the eggs until hatching. Following hatching many initiated another spawning cycle. One male was reproductively active for 73 days during which it completed five distinct reproductive cycles. Spawning extended throughout the year.     

Determining the optimum temperature and salinity for larval culture,and describing a culture protocol for the conservation aquaculture for European smelt Osmerus eperlanus (L.)

Populations of anadromous European smelt Osmerus eperlanus (L.) are declining across its geographical range in northern Europe, but no practical culture techniques exist to develop stock enhancement programmes for this species. In this study, a culture protocol is described to rear fish from fertilised eggs to mature adults in 2 years involving the use of ‘green water’, live feed and artificial diets. The sequence of embryonic development for eggs incubated at 10°C/0 ppt was described and photographed. To determine the optimum conditions for larval culture, fertilised eggs were reared at a range of salinities (0–20 ppt) and temperatures (5–18°C) until first feeding. Best hatching success (ca. 97%), size at hatch (ca. 0.8 mm) and survival to first feeding (ca. 96%) of larvae were achieved under combined conditions of low salinity (0–0 ppt) and temperature (5–10°C). No larvae survived a salinity of 20 ppt. The time taken from fertilisation to hatch (FtH) and hatching duration (HD) were temperature-dependent ranging from 42 days FtH and 10 days HD at 5ºC, to 10 days FtH and 2 days HD at 18°C irrespective of salinity. The results indicate that conservation programmes could utilise existing salmonid hatchery facilities (i.e. freshwater, ≤10°C water temperature) for stock enhancement. Since on-growing of smelt involves the logistical and technical problems of live feed production, it is recommended that smelt enhancement programme utilise freshwater hatchery facilities to rear fish until hatching, and then stock out onto known spawning grounds in rivers allowing hatched larvae to drift into estuaries to complete the larval and juvenile phases. This approach would minimise the time spent in the hatchery post-hatching, eliminate the need for live food production, prevent the development of predator-naïve fish, and hence would mimic the natural life cycle of the species as closely as possible.     

Lunar periodicity in the spawning of yellowtail damselfish,Microspathodon chrysurus

Synopsis The reproductive behavior of yellowtail damselfish,Microspathodon chrysurus, was studied off the Caribbean coast of Panama to determine if there is a lunar spawning cycle. Male damselfish prepare nest sites on dead coral surfaces within their permanent feeding territories. Spawning occurs at sunrise and lasts for approximately one hour. Males defend the eggs until hatching, which occurs before the morning of the sixth day of incubation. Males spawn only once a day, but may spawn many times within each reproductive phase. Reproductive activity is highest in the time periods from full to new moon. The timing of this lunar cycle differs from those reported for other marine fishes. The spawning pattern is not consistent with common explanations for lunar periodicity that are based on the role of tides or moonlight. Some implications of these results for the organization of tropical reef communities are discussed.     

Mass spawning of Caesio teres (Pisces: Caesionidae) at Enewetak Atoll,Marshall Islands

Synopsis Mass spawning of Caesio teres occurred between March and August, 1983 on a reef emerging from deep water just inside the East Channel of Enewetak Atoll, Marshall Islands. Aggregations and spawning were observed from one day before until three days after the full moon. Spawning aggregations were not observed during the new or quarter moons. Spawning commenced after high tide, when the current began to flow out the pass from lagoon to ocean. The spawning aggregation of close to 1000 individuals migrated to the spawning site. Spawning occurred when the aggregate ascended to near the water's surface. Subgroups dashed horizontally within the aggregate, releasing a highly visible gamete cloud. Predation on spawning adults was not observed. Predation on spawned eggs was noted. The eggs of C. teres are described. Mid-Pacific Research Laboratory, Enewetak Atoll, Republic of the Marshall Islands Present address: Motupore Island Research Station, P.O. Box 320, University of Papua New Guinea, Papua New Guinea     

Mating system and spawning cycle in the blenny,Istiblennius enosimae,at Kagoshima,Japan

Synopsis Field observations on reproductive ecology and territoriality of the blennyIstiblennius enosimae, were made in a tidepool at Hanaze Beach, Kagoshima Prefecture, Japan during the summer of 1988. This blenny was herbivorous, and nesting males (> 73 mm SL) maintained territories around nest sites, which were located in rocky crevices of the tidepool. Males courted females wandering near their nests, and spawnings coincided with neap tides. Males guarded the eggs until the embryos hatched at following spring tides. It was suggested that this semilunar spawning cycle guarantees a maximum dispersal of newly hatched embryos away from natal tidepool. Male reproductive success was related to large body size and/or large nest size. There is a size-assortative relationship between male and female among pairs. Egg predation rates by fishes, crabs and sea urchins were not correlated with the body size of male blennies.     

Winter aspects of the ichthyoplankton community in Antarctic Peninsula waters

Summary Ichthyoplankton was sampled from the Antarctic Peninsula area of the South Polar Ocean in early winter (May and June 1986). A total of 153 eggs from two species and 1368 larvae or juvenile stages from 12 species were obtained. These included pelagic species, and demersal species with a long pelagic larval or juvenile phase. Most abundant were larvae of Pleuragramma antarcticum and Notothenia kempi, and eggs of Notothenia neglecta. The distribution of notothenioid and paralepidid larvae was apparently unaffected by ice cover, whereas myctophid larvae were confined to ice-free waters. Areas where newly hatched Chionodraco hamatus occurred coincided with dense aggregations of Euphausia superba (Krill) furcilia larvae which is a potential food resource during winter. The hatching of icefish larvae during winter is apparently independent of the seasonal production cycle. Epipelagic eggs of Notothenia neglecta were found during the spawning season, which suggests that eggs ascend to the surface after demersal spawning and that development takes place near the sea surface during winter. Larvae of Notothenia kempi were chiefly confined to shelf and slope waters to the west of the Antarctic Peninsula, with larger larvae found in coastal shelf areas. Pleuragramma antarcticum occurred in the coastal waters off the Biscoe Islands, in the Gerlache Strait, and in the northern Bransfield Strait. The smallest larvae were found in the northern Bransfield Strait, whereas those at the Biscoe Islands and in Gerlache Strait waters were larger and of a similar size. A cyclonic gyre to the west of the Antarctic Peninsula observed in the austral summer was likely to have affected the larval drift of Pleuragramma antarcticum and Notothenia kempi. Differences in the timing of spawning and hatching and the vertical distribution of these larvae will lead to different transport and spatial distribution patterns. It is hypothesized that early winter conditions do not imply severe limitations on the year-class success of larval fish. Dispersal and increased mortality may occur during the second half of the winter.     

Evolution of Female Egg Care in Haremic Triggerfish,Rhinecanthus aculeatus

Paternal care is predominant among telcost fishes with external fertilization. This study describes maternal care in a haremic coral-reef fish and discusses the possible factors leading to its evolution. Both sexes of the triggerfish Rhinecanthus aculeatus (Balistidae) maintained territories; some individuals for more than 8 years. Each male's territory overlapped 2-3 female territories. Pair-spawning occurred around sunrise. Only females cared for the demersal eggs until hatching, which occurred just after sunset on the day of the spawning. No predation was observed on eggs under the maternal care, but experimental removal of parental females decreased the hatching rate to nearly zero. Egg-guarding females foraged as frequently as males, but less than half of non-spawning days. Spawning occurred only in the periods of about 1 wk around the new or full moon, and individual females spawned up to three times in each period. Thus, the maternal care did not significantly affect the duration of the females' spawning intervals, while males would suffer mate loss if they performed parental care. In this situation, maternal care should be the evolutionarily stable strategy. Evolutionary transition from no care to maternal care and then to biparental care is suggested in the Balistidae.     

Using drift nets to capture early life stages and monitor spawning of the Yangtze River Chinese sturgeon (Acipenser sinensis)

A sampling system for capturing sturgeon eggs using a D-shaped bottom anchored drift net was used to capture early life stages (ELS) of Chinese sturgeon, Acipenser sinensis , and monitor annual spawning success at Yichang on the Yangtze River, 1996–2004, before and just after the Three Gorges Dam began operation. Captured were 96 875 ELS (early life stages: eggs, yolk-sac larvae = eleuthero embryos, and larvae); most were eggs and only 2477 were yolk-sac larvae. Most ELS were captured in the main river channel and inside the bend at the Yichang spawning reach. Yolk-sac larvae were captured for a maximum of 3 days after hatching began, indicating quick dispersal downstream. The back-calculated day of egg fertilization over the eight years indicated a maximum spawning window of 23 days (20 October–10 November). Spawning in all years was restricted temporally, occurred mostly at night and during one or two spawning periods, each lasting several days. The brief temporal spawning window may reduce egg predation by opportunistic predators by flooding the river bottom with millions of eggs. During 1996–2002, the percentage of fertilized eggs in an annual 20-egg sample was between 63.5 to 94.1%; however, in 2003 the percentage fertilized was only 23.8%. This sudden decline may be related to the altered environmental conditions at Yichang caused by operation of the Three Gorges Dam. Further studies are needed to monitor spawning and changes in egg fertilization in this threatened population.     

Field and laboratory observations of spawning periodicity and behavior of a northern population of the Atlantic silverside,Menidia menidia (Pisces: Atherinidae)

Synopsis The spawning periodicity and mating behavior of a northern population of the Atlantic silverside, Menidia menidia, was studied both in the field (Salem Harbor, Massachusetts) and in laboratory experiments. Spawning in the field coincided with new and full moons. Under conditions of unlimited food availability in artificial outdoor pools that received natural celestial illumination or in indoor aquaria receiving no evening illumination, spawning occurred every 1–3 days rather than fortnightly. These results suggest that tidal influences are a primary factor that synchronizes spawning in M. menidia. Published reports of diel time of spawning in both marine and freshwater species of Menidia indicate a generic tendency to spawn during mid-morning. This pattern coupled with high tides that cover suitable spawning substrates during mid-morning only at fortnightly intervals could account for the semilunar spawning cycle in marine populations of Menidia. Although general characteristics of the reproductive ecology of M. menidia in Massachusetts were similar to a thoroughly studied population in South Carolina, several differences were evident. The breeding season was shorter in Massachusetts (late; April–June), and occurred over a much lower range of temperatures (9–21°C). Intensity and frequency of spawning was correlated with the height of high tide. Eggs were deposited only on mats of intertidal, filamentous algae rather than on roots or stems of Spartina alterniflora or other intertidal vegetation. Promiscuous spawning occurred in small, highly male-dominated groups of fish, primarily after the tide had begun to recede, and often at the water's edge. No predation on spawning adults was observed but the mummichog, Fundulus heteroclitus, fed daily on developing embryos during high tide. Contribution No. 81, Massachusetts Cooperative Fisheries Research Unit, Contribution No. 349, Marine Sciences Research Center, State University of New York at Stony Brook.     

Spawning timing of the cleaner wrasse, Labroides dimidiatus, on a warm temperate rocky shore

We observed spawning behaviors of the haremic cleaner wrasse Labroides dimidiatus at a rocky reef in southern Japan. Females released pelagic eggs daily from June to September after a spawning ascent by pairs. When the high tide occurred between noon and evening (quarter moon to new or full moon), they spawned around the time of the tide providing fast offshore currents. For the rest of the lunar cycle, spawnings occurred during late afternoon independent of the state of the tide at the time of day. This spawning pattern is quite different from that of conspecifics on coral reefs that always spawn around the high tide at all lunar stages to avoid potential egg predators. The wrasse ascended high in the water column, probably because of its predator-immune characters as a cleaner. The steep slope of the study site seemed to contribute to releasing gametes far above aggregating planktivores. Thus, gametes were not subject to heavy predation. Current direction might not always affect survival of spawned pelagic eggs on the temperate reefs so crucially as it does on coral reefs. We conclude that spawning during unfavorable tidal conditions during the daytime may be better than spawning during the best tidal condition in the crepuscular period when predation pressure on adults will be high. Intraspecific variation in the timing and location of spawning of the wrasse may result from different conditions for larval survival. Received: February 6, 2000 / Revised: June 16, 2000 / Accepted: July 17, 2000     

The breeding behavior and the behavior of larvae and juveniles of the sharksucker,Echeneis naucrates

Eleven sharksuckers,Echeneis naucrates, in the Oita Ecological Aquarium spawned from 2 June to 3 December 1974. The spawning behavior began as soon as the lights were turned off. Just before a female spawned, it was driven toward the surface of the water by a group of males. The spawned eggs were pelagic and 2.6 mm in diameter. Approximately 500 eggs were spawned each day. Seventy larvae were hatched on 15 July, and 26 of them were reared until 1 September. We observed the behavior of their larvae and juvenile stages, from the hatching to the attaching phases. The caudal fins of the larvae expanded as they grew. They swam near the bottom with their caudal fins folded. When the sucking disk began to form on the back of a larva’s pectoral fin, it stood still with its caudal fin bent on bottom. After the formation of the sucking disk, a larva would lie on its stomach or back. Some quickly-growing specimens began to stick to the walls, pipes, or plates when they attained 55 mm SL, 35 days after hatching.     

Embryonic and larval development of a Japanese spinous loach,Cobitis takatsuensis

The embryonic and larval development ofCobitis takatsuensis, a mountain stream spinous loach, was surveyed by incubating artificially inseminated eggs. The mean diameter of the inflated eggs and mean total length of newly-hatched larvae were 2.7 mm and 5.7 mm, respectively. The eggs were spherical, transparent and unpigmented, with a pale yellow yolk and no oil globule. The daily cumulative temperature to hatching was estimated to be 70–110°C. day. Hatched larvae were unpigmented with outer gill filaments on their cheeks, as in otherCobitis species, but the melanophores were comparatively less obvious at each developmental stage. The larvae started feeding eleven days after hatching yolk absorption being completed sixteen days after hatching. All the fin rays were fully developed and the juvenile stage reached at 16 mm TL, 38 days after hatching. Embryonic and larval developmental traits ofC. takatsuensis, such as egg size, clutch size and larval pigmentation, were similar to the Korean species,Niwaella multifasciata, that lives in the upper reaches of the Nak-tong river, andN. delicata, which inhabits Japanese mountain streams, rather than to its congeners. Among cobitine fishes, the spawning of a small number of larger eggs yielding larger larvae without pigmentation, characteristics shared byC. takatsuensis, N. multifasciata andN. delicata, is attributable to adaptation to cold mountain streams.     

Spawning frequency, fecundity, egg weight and spawning type of silver pomfret, Pampus argenteus (Euphrasen) (Stromateidae), in Kuwait waters

Silver pomfret, Pampus argenteus, were collected by fishing with drift gillnets on one spawning ground in Kuwait waters during 1998–2000. Fish size frequency, sex ratio, maturation cycle, spawning frequency, fecundity and egg weight were assessed. The length–weight relationship differed between sexes whereby females were significantly bigger than males. Spawning started in mid‐May and continued until early October. During this time the water temperature ranged from 26.0 to 32.8°C, salinity was ? 39.0‰ and water depth ranged between 5 and 12 m. Large females spawned earlier than young spawners and the overall percentage of males during the spawning period was 70.3%. Spawning occurred after 13.00 h, with peak spawning between 15.00 and 18.00 hours during outgoing tide. Mean daily spawning frequency amounted to 63.2%. Spawning activity was found to be associated with the lunar cycle and spawnings were concentrated during the first and third quarters of the moon period, indicating a semilunar reproduction cycle. It was concluded that a female would spawn at least six times during the season. No change was observed in relative fecundity during the peak spawning season (June–August). Average relative batch fecundity was 176.3 eggs g^?1 somatic weight (SW), corresponding to a relative total fecundity of 1058 eggs g^?1 SW, which is 1.5 times higher than estimates obtained from counting the standing stock of oocytes. Bigger fish produced heavier eggs and the egg weight decreased as the spawning season progressed. Based on gonadal cycles, oocyte size frequency distribution and total fecundity, we concluded that silver pomfret is a multiple batch spawner with indeterminate fecundity.     

Non-copulatory spawning and female participation during early egg care in a marine sculpinHemilepidotus gilberti

The reproductive behavior of a marine sculpin,Hemilepidotus gilberti, was observed in the aquarium. The behavioral sequence comprised fight for terriotory, courtship and fight for females, spawning and caring for the egg mass. Females very slowly deposited eggs enclosed with viscous ovarian fluid onto the substrate. Almost all the eggs contained in the ovary were released in a single spawning, its completion requiring 21–22 min. Territorial males emitted of spawning. Sneaking by neighboring males followed subsequently. This was the first observation of non-copulatory spawning among marine sculpins. Females cared for the eggs for severl days after spawning, and then male alone care continued until hatching (47–49 days after spawning). Participation by females in egg caring is likely to be caused by their spawning only once during the spawning season and the consequent lack of urgency for post-spawning feeding.     

Parental investment of male two-spotted goby, Gobiusculus flavescens (Fabricius)

The trade-off between parental care and feeding was studied in the male two-spotted goby (Gobiusculus flavescens F.). Two temperatures, 8.5 degrees C and 13.0 degrees C, were used, with five replicates at each temperature, in order to determine whether temperature influenced parental behaviour. In each replicate, two males and four females were introduced to an aquarium, where the males chose between two nests and courted the females. In each replicate, one male spawned. After spawning, the males guarded the eggs until hatching. The guarding males' behaviour was recorded with a video camera twice a day (15 min each time), once before and once after they were fed. The male's condition (c-factor) was calculated at the start of the experiment and after egg hatching. The eggs were spawned in an artificial nest (half of a PVC tube), and attached to the nest in a single layer. The areas with eggs (representing brood size) were marked after spawning and the fry counted after hatching (which was used to calculate area hatched). Numbers of prey eaten (plankton) and number of aggressive encounters between the guarding male and the other fishes were recorded. Time spent in the nest and time used on fertilisation, fanning and cleaning were estimated and related to egg age, brood size, hatching success, temperature and food availability (no food or food).The results showed that feeding (expected to influence future reproduction) decreased and parental expenditure (current reproduction) increased, as the eggs developed (became closer to independence). Parental expenditure was significantly higher at 13.0 degrees C than at 8.5 degrees C, presumably due to higher oxygen demands by the eggs, and a greater risk of egg-infections. The c-factor of the males guarding eggs decreased over time, in contrast to the non-guarding males' c-factor. Guarding males' aggressiveness decreased as the eggs got older, but increased just before hatching. A possible explanation for this could be the decreasing intrusion by the non-guarding male and females caused by high aggressive behaviour by the guarding male early in the brood cycle. The exploitation of the nest (percentage of total nest area covered by eggs) seemed to determine the amount of parental expenditure and loss of condition, while brood size (area of eggs) had no effect.     

Breeding pattern and nest guarding in Sicyopterus lagocephalus, a widespread amphidromous Gobiidae

Amphidromous gobies are usually nest spawners. Females lay a large number of small eggs under stones or onto plant stems, leaves or roots while males take care of the clutch until hatching. This study investigates the breeding pattern and paternal investment of Sicyopterus lagocephalus in a stream on Reunion Island. In February 2007 and January 2010, a total of 170 nests were found and the presence of a goby was recorded at 61 of them. The number of eggs in the nests ranged from 5,424 to 112,000 with an average number of 28,629. We showed that males accepted a single female spawning in the nest and cared for the eggs until hatching. The probability for a nest to be guarded increased with the number of eggs within it, suggesting that paternal investment depends on a trade-off between the reproductive value of the current reproduction and future nesting events. We showed that large nest stones were occupied by large males (TL >80 mm), whereas smaller males (TL <50 mm) were found under smaller cobbles, probably because of male–male competition for available nests. Our results suggest that the male’s choice relies upon a similarity to the female size, while the female’s choice was based on both body and nest stone sizes.     

Reproduction and development of the weakly electric fish,Pollimyrus isidori (Mormyridae,Teleostei) in captivity

Synopsis No clear sexual dimorphism occurs in Pollimyrus isidori. Females usually grew slightly larger than males. The anal-fin reflex, however, makes it easy to discriminate between males and females. Spawning took place during the first six hours of the dark phase, in the territory of the male. During each spawning act 2–4 eggs were laid. The male put the eggs into a well-hidden nest previously constructed from plant material. The eggs, free embryos, and larvae of several spawnings were guarded by the male for several weeks. The females laid on average 120 eggs per fractional spawning. The eggs were 2 mm in diameter, not adhesive and very yolky. There was a relationship between pH and viability (% embryos hatched). Hatching occurred on the third day after spawning. The respiratory network of segmental origin in the median fin fold was well developed in the free embryos. Transition to exogenous feeding occurred on day 14. The larval period ended when the fish were 15 mm long and 40–50 days old. First gonadal recrudescence occurred at a total length of 6 cm (about 200 days old). The environmental factors decreasing conductivity and pH, increasing water level, and imitation of rain led to gonadal recrudescence, but pH did not act as a cue. Recrudescence was triggered by a decrease of conductivity, but absolute values or ionic composition of the water were not important. Maturation was completed after about fifty days. Mature and spawning fish no longer required any variation of these environmental factors to maintain mature gonads. A steady and considerable increase in conductivity led to gonadal regression. The fish did not show postbreeding refractoriness.     

4. A FIELD NATURALIST'S PEREGRINATIONS. BIRD NOTES FROM A NORTHERN SECTOR OF SOUTHERN RHODESIA—Part III

Boyer, H. J. 1988. Breeding biology of the Dune Lark. Ostrich 59:30-37.

The peak of the breeding season of the Dune Lark Mirafra erythrochlamys occurred in January and February and was not dependent on rainfall. Most nests were domed, although one undomed nest was recorded. Ninety-one percent of clutches were of two eggs (mean = 1,9; range 1–2; n = 11). The eggs are described and measurements given. Incubation, by the female only, began with the laying of the second egg, and hatching occurred after 13–14 days. Growth and development of nestlings are described. The young left the nest after 12–14 days, and post-nestling parental care lasted for approximately one month. Sixty-one percent of eggs hatched. and 28% produced young which successfully left the nest. Most losses of eggs and young were the result of predation.