Distribution by Scientific Domains

Kinds of Spawning

  • fish spawning
  • natural spawning
  • salmon spawning

  • Terms modified by Spawning

  • spawning activity
  • spawning area
  • spawning behaviour
  • spawning event
  • spawning ground
  • spawning habitat
  • spawning locations
  • spawning migration
  • spawning period
  • spawning season
  • spawning site
  • spawning stock
  • spawning stock biomass
  • spawning success
  • spawning time

  • Selected Abstracts

    Using underwater cameras to describe the reproductive behaviour of the endangered eastern freshwater cod Maccullochella ikei

    G. L. Butler
    Abstract,,, Underwater cameras were used to observe the breeding behaviour of the endangered eastern freshwater cod, Maccullochella ikei, over 3 years and across three areas in the Mann and Nymboida rivers, Australia. The annual breeding season for M. ikei was short and succinct, lasting only 8,10 weeks. Spawning commenced each year in the lowest altitude area during the first week of spring, and approximately 1 week later in the closest upstream area. Day-length is the primary spawning cue for M. ikei, but increasing water temperature may also be of importance. Nesting sites were located in slow-flowing pools, under cover such as large boulders and bedrock shelves, at depths of 0.9,4.0 m, and with one or two entrances only. The nesting site was vigorously cleaned by the male up to 1 week prior to spawning and was only entered by the female for spawning. Paternal care of eggs and larvae was undertaken for up to 24 days, after which larvae dispersed. Greater protection of breeding M. ikei must be a management priority to ensure long-term conservation of the species. [source]

    Contemporary egg size divergence among sympatric grayling demes with common ancestors

    F. Gregersen
    Abstract, This study documents divergence in egg size that has occurred over less than 25 generations among sympatric demes of European grayling (Thymallus thymallus) from Lake Lesjaskogsvatnet in Norway. A cluster analysis identified two clusters of tributaries: one of small, warm tributaries (SW) and the other of large, cold tributaries (LC). Spawning occurs more regularly and up to 4 weeks earlier in SW tributaries compared with that in LC ones. We explored numerous mixed models predicting egg size from year (random effect), basin and tributary (fixed effects), and female length. The most supported model estimated length-adjusted egg size to be larger in SW tributaries compared with that in LC tributaries. Combinations of density-dependent (competition for food/space) and density-independent (temperature) factors along with phenotypic plasticity and maternal effects are discussed as potential differentiation sources. We suggest high temperatures (increased metabolism) to reinforce the selective advantage of large eggs under conditions with highly density-dependent fry interactions. [source]

    Introducing size limits as a management tool for the recreational line fishery of silver kob, Argyrosomus inodorus (Griffiths and Heemstra), in Namibian waters

    C. H. Kirchner
    Individual silver kob Argyrosomus inodorus (Griffiths and Heemstra) first mature at just over 1 yr of age and the median age at maturity is approximately 1.5 yr. Spawning of silver kob was observed in the southern and central region of the stock's range, but little spawning activity was found in silver kob sampled from the northern region. The spawning period is protracted over 6 months (October,March), which coincides with warmer water temperatures (>15 C) and the occurrence of large-sized spawning silver kob in the southern and central part of Namibia. Implementing a minimum size limit for the silver kob fishery is not recommended as it will have serious economic implications for the coastal communities. The protection of the spawning areas, Meob Bay and Sandwich, should be continued and a strict bag limit on large-sized silver kob is recommended for the Namibian silver kob recreational fishery. [source]

    Ichthyoplankton-based spawning dynamics of blue mackerel (Scomber australasicus) in south-eastern Australia: links to the East Australian Current

    Abstract We describe findings of three ichthyoplankton surveys undertaken along south-eastern Australia during spring (October 2002, 2003) and winter (July 2004) to examine spawning habitat and dynamics of blue mackerel (Scomber australasicus). Surveys covered ,860 nautical miles between southern Queensland (Qld; 24.6S) and southern New South Wales (NSW; 41.7S), and were mainly centred on the outer shelf including the shelf break. Egg identifications were verified applying mtDNA barcoding techniques. Eggs (n = 2971) and larvae (n = 727; 94% preflexion) occurred both in spring and winter, and were confined to 25.0,34.6S. Greatest abundances (numbers per 10 m2) of eggs (1214,7390) and larvae (437,1172) occurred within 10 nm shoreward from the break in northern NSW. Quotient analyses on egg abundances revealed that spawning is closely linked to a combination of bathymetric and hydrographic factors, with the outer shelf as preferred spawning area, in waters 100,125 m deep with mean temperatures of 19,20C. Eggs and larvae in spring occurred in waters of the East Australian Current (EAC; 20.6,22.3C) and mixed (MIX; 18.5,19.8C) waters, with none occurring further south in the Tasman Sea (TAS; 16.0,17.0C). Results indicate that at least some of the south-eastern Australian blue mackerel stock spawns during winter-spring between southern Qld and northern NSW, and that no spawning takes place south of 34.6S due to low temperatures (<17C). Spawning is linked to the EAC intrusion, which also facilitates the southward transport of eggs and larvae. Since spring peak egg abundances came from where the EAC deflects offshore, eggs and larvae are possibly being advected eastwards along this deflection front. This proposition is discussed based on recent data on blue mackerel larvae found apparently entrained along the Tasman Front. [source]

    Early life history of the Mediterranean gorgonian Paramuricea clavata: implications for population dynamics

    Cristina Linares
    Abstract. Knowledge about early stages of marine sessile invertebrates dispersing by means of free-swimming propagules is fundamental toward understanding their population biology. In this study, we describe and quantify survivorship of early stages of the gorgonian Paramuricea clavata to contribute to the understanding of their implications on population dynamics of this emblematic species of the Mediterranean hard-bottom communities. Spawning was recorded in June for the 3 years studied (2001,2003). High levels of fertilization rate were observed during the main spawning in 2001 and 2002 (62,69%). This appears to be related to the surface brooding mode of development, synchronous spawning, and high fecundity of the species. The timing of development of the blastulae was ,24 h and the planulae appeared after 48,72 h. In the laboratory, metamorphosis into polyp started between 8 and 25 d, but this timing may have been delayed by lack of unknown appropriate cues for settlement. The behavior of first developed planulae exhibited a marked negative phototaxis that may be a strategy to avoid competition with fast-growing algae on photophilous habitats. Despite the high fertilization rate in P. clavata, laboratory and field experiences indicate that survivorship through the planulae and polyp stages was very low, given that none of the settled polyps survived for >7 months in both experimental years. The low survival of the early stages may help explain the low recruitment rates observed in the field in addition to indicating major limitations for colonization of new areas and for persistence of the local population under disturbances. [source]

    Recruitment and growth of two small-bodied resident fish species (Gobiidae and Atherinidae) in oligohaline, seasonally open lagoons

    P. G. Close
    Spatio-temporal recruitment patterns, growth and survival of the Swan River goby Pseudogobius olorum and western hardyhead Leptatherina wallacei are described from two small, coastal lagoons on the south coast of Western Australia. In these lagoons, estuarine salinity dynamics were relatively stable over much of the autumn,spring period when freshwater inputs from rivers were reduced and there was no oceanic connection. Preflexion and flexion stages of both fish species contributed strongly to population size structure in downstream reaches, whereas upstream reaches were dominated by postflexion larvae and juvenile stages. Spawning of both species was protracted and largely asynchronous, although the episodic presence of stronger preflexion and flexion cohorts suggested some synchronized spawning had occurred. Comparison with estuarine conditions over this period provided evidence that synchronized spawning may be related to temperature and salinity variations from a combination of freshwater inputs and periods of marine exchange. Uninterrupted growth and the progression of cohorts through to juvenile stages were consistent with the generally stable estuarine conditions. Larval and juvenile stages of both species were also tolerant of abrupt changes in salinity and temperature, which occurred due to a non-seasonal oceanic connection. These findings were consistent with the euryhaline nature of adults of both species. [source]

    Spawning dynamics and biomass estimates of an anchovy Engraulis australis population in contrasting gulf and shelf environments

    W. F. Dimmlich
    The spawning biomass of Australian anchovy Engraulis australis in gulf and shelf waters of South Australia was compared using the daily egg production method (DEPM). The total survey area was 128 700 km2 with recorded spawning areas in gulf and shelf waters of 4898 and 44 618 km2, respectively. High egg densities in the warm, shallow gulf waters were produced by small, young (<1 year old) E. australis that spawned relatively small batches of eggs (c. 855) approximately every 3 days. In cooler, deeper shelf waters, where larger, older E. australis are found, lower egg densities occurred despite individuals producing much larger batches of eggs (c. 15 572) approximately every 7 days. In shelf waters, the highest densities were recorded at inshore sampling stations. Spawning appeared to peak between 0000 and 0100 hours. Females were more abundant than males in samples from both gulf and shelf waters with sex ratios of 061 and 056, respectively. The spawning biomass of E. australis in shelf waters was 101 522 t, whereas the estimate for gulf waters was 25 374 t. Due to the differences in mean size of the spawning females, however, c. 6 109E. australis were present in each region. The results support the hypothesis that variability in habitat conditions may directly influence E. australis reproduction. A large reserve of young fish in the relatively stable gulf environment may increase the resilience of the E. australis population in South Australia to unfavourable interannual changes in offshore environmental conditions. [source]

    Oceanic migration and spawning of anguillid eels

    K. Tsukamoto
    Many aspects of the life histories of anguillid eels have been revealed in recent decades, but the spawning migrations of their silver eels in the open ocean still remains poorly understood. This paper overviews what is known about the migration and spawning of anguillid species in the ocean. The factors that determine exactly when anguillid eels will begin their migrations are not known, although environmental influences such as lunar cycle, rainfall and river discharge seem to affect their patterns of movement as they migrate towards the ocean. Once in the ocean on their way to the spawning area, silver eels probably migrate in the upper few hundred metres, while reproductive maturation continues. Although involvement of a magnetic sense or olfactory cues seems probable, how they navigate or what routes they take are still a matter of speculation. There are few landmarks in the open ocean to define their spawning areas, other than oceanographic or geological features such as oceanic fronts or seamounts in some cases. Spawning of silver eels in the ocean has never been observed, but artificially matured eels of several species have exhibited similar spawning behaviours in the laboratory. Recent collections of mature adults and newly spawned preleptocephali in the spawning area of the Japanese eel Anguilla japonica have shown that spawning occurs during new moon periods in the North Equatorial Current region near the West Mariana Ridge. These data, however, show that the latitude of the spawning events can change among months and years depending on oceanographic conditions. Changes in spawning location of this and other anguillid species may affect their larval transport and survival, and appear to have the potential to influence recruitment success. A greater understanding of the spawning migration and the choice of spawning locations by silver eels is needed to help conserve declining anguillid species. [source]

    Reproductive biology of two co-occurring mugilids, Liza argentea and Myxus elongatus, in south-eastern Australia

    B. W. Kendall
    The reproductive biology of Liza argentea and Myxus elongatus occurring in two estuaries (Lake Macquarie and St Georges Basin) was found to differ. Gonado-somatic index values and macroscopic staging of gonads identified the peak spawning period of L. argentea occurred between March and November in Lake Macquarie and January and April in St Georges Basin. In contrast, peak spawning of M. elongatus was concentrated between January and March in both estuaries. Spawning of L. argentea probably occurred in the lower reaches of estuaries as well as in nearshore coastal waters, whereas evidence indicated M. elongatus spawned only in ocean waters. The mean fork length at maturity (LF50) was greater for females than males in both species, and it also occurred at a larger mean LF in M. elongatus (males = 230 mm and females = 255 mm) than L. argentea (males = 180 mm and females = 207 mm). Estimates of total potential fecundity were also greater for M. elongatus (425 484,1 157 029) compared to L. argentea (159 933,548 954). Both species had determinate fecundity and displayed a group synchronous pattern of oocyte development, with two distinct size classes of oocytes present in mature ovaries. Liza argentea probably release the larger class of oocytes in one spawning event, but this could not be established for M. elongatus. [source]

    Reproductive behaviour of a temperate serranid fish, Paralabrax clathratus(Girard), from Santa Catalina Island, California, U.S.A.

    B. E. Erisman
    The reproductive behaviour of the kelp bass Paralabrax clathratus was studied on Santa Catalina Island, California, U.S.A. from April 2000 to September 2002. Adults formed aggregations of three to > 200 individuals, and spawning occurred within subgroups of three to 23 individuals that contained a single female. The gonado-somatic index (IG) of collected ripe males (mean = 58%, range = 05,131%) indicated a large investment in sperm production that is common in group-spawning fishes characterized by intense sperm competition. Spawning occurred 32 min before sunset to 120 min after sunset, and both males and females were capable of spawning multiple times during a single evening. Behavioural observations of adults and estimates of spawning periodicity from the collection of females with hydrated oocytes suggested that spawning occurred continuously throughout the summer months and showed no significant relationship with the lunar cycle. In general, the spawning behaviour of kelp bass was similar to other functionally gonochoric, group-spawning serranids. The dynamics of P. clathratus spawning aggregations, however, were inconsistent with that of tropical reef fish spawning aggregations, including the transient spawning aggregations of some tropical serranids. Aggregation spawning appeared to be an important component of the annual reproduction of this species. [source]

    Effect of dietary cortisol administration on growth and reproductive success of channel catfish

    B. C. Small
    The effect of cortisol administration on reproductive performance was investigated in channel catfish Ictalurus punctatus broodfish. Cortisol was added to a commercial catfish feed by dissolving in ethanol and spraying the feed to yield a dietary concentration of 150 mg kg,1 feed. The cortisol diet and the control (no cortisol) diet were offered at a rate of 1% of biomass to three replicate ponds each containing 28 female and 14 male broodfish, respectively, three times per week for 11 weeks. Spawning began 10 days after the start of the experiment, and continued for 10 weeks. In fish fed cortisol, body mass and the hepato-somatic index were reduced (P , 002) and concentrations of plasma cortisol and glucose were significantly higher (P , 00003) compared to those of controls. The relative frequency of spawning was similar between the two treatments; however, cortisol-fed channel catfish had an average of 471% more spawns than the control-fed fish. On average, there were 255 spawns per pond in the treated groups compared to 123 spawns per control pond (P = 010). No effect was observed on egg production, with individual egg mass, fecundity, and hatching success being similar (P , 027) for both treatments. Despite the observed negative effects of cortisol on somatic and hepatic growth, the increased reproductive output coupled with no observable effects on the eggs or hatching success demonstrates that cortisol does not suppress channel catfish reproduction. [source]

    Reproductive migration of brown trout in a small Norwegian river studied by telemetry

    A. Rustadbakken
    The movement of 34 large (39,73 cm standard length) brown trout Salmo trutta was monitored using radio telemetry for up to 74 days in Brumunda, a small Norwegian river (mean annual discharge 33 m3 s,1) flowing into the large Lake Mjsa. The maximum range of movement in the river was 20 km. No clear relationships existed between individual movement and water discharge, temperature and barometric pressure. Brown trout migrated at all levels of water discharge. At low discharge (<2 m3 s,1) movements were nocturnal. A weir 53 km from the outlet restricted ascending brown trout at low (c. 6 C), but not at high (c. 8 C) water temperatures. Spawning occurred in September to October and tagged individuals spent 2,51 days at the spawning sites. Mean migration speed from tagging to when the fish reached the spawning area, and from when they left the spawning areas and reached the lake was 10 and 23 km day,1, respectively. All tagged brown trout that survived spawning returned to the lake after spawning. [source]

    Characteristics of egg and larval production in captive bluespotted gobies

    L. A. Privitera
    Spawning of the Hawaiian coral-reef goby Asterropteryx semipunctata was diurnal, occurring at various times throughout the day. Mean length of eggs deposited in nests was 076 mm (range 067,084); mean egg width was 047 mm (range 041,052). Clutch size varied from 296 to 1552 eggs (mean=886309), and was independent of standard length, total body weight, and body condition. Mean relative clutch size was 159 eggs mg -1 total body weight (range 084,243). Clutches hatched 4,5 nights after being deposited in a nest. Mean notochord length of newly-hatched larvae was 188 mm (range 160,204). The minimum period of time that elapsed between egg deposition and subsequent growth of a new batch of oocytes to spawning size was 5,6 days, providing a reasonable estimate of minimum spawning interval. Compared with other gobiids, tropical species tend to have shorter incubation periods, smaller eggs and smaller larvae at hatching. [source]

    Laboratory Study of the Intracapsular Development and Juvenile Growth of the Banded Murex, Hexaplex trunculus

    Youssef Lahbib
    Spawning, intracapsular development, and juvenile growth of Hexaplex trunculus were investigated in the laboratory. Each female deposited nightly an average of 138.83 58.70 yellowish egg capsules per spawn. Each capsule contained 358.57 102.45 eggs with an average diameter of 207.23 18.18 m. Observations on the intracapsular development showed that H. trunculus is a spiralian unequal-cleaving gastropod, with polar lobes being extruded at early segmentation. Embryos develop within the egg capsule through the provision of nurse eggs as an extraembryonic source of nutrition. Hatching occurred after 52 d of incubation. However, the hatchlings were not completely metamorphosed because velum was still present. At this moment, the average of shell length was 1.04 0.13 mm (n = 107). The average number of hatchlings per capsule was 14.73 4.40 including 3.4% malformed individuals. During the first 5 mo of life, juveniles rapidly grew in shell length (growth rate = 3.56 mm/mo). However, in the remaining period (26 mo), growth rhythm decreased considerably (growth rate = 0.64 mm/mo). The weight growth rhythm was irregular with alternation between fast and slow increases observed over the rearing experiment. This kind of data could be useful for assessing the potential of this species for future molluscan aquaculture programs. [source]

    Spontaneous Spawning of Captive Red Snapper, Lutjanus campechanus, and Dietary Lipid Effect on Reproductive Performance

    Nikolaos Papanikos
    Two experiments addressed the spontaneous spawning of red snapper, Lutjanus campechanus, under controlled temperatures and photoperiods and the effect of broodstock diets supplemented with oils rich in polyunsaturated fatty acids. In Experiment 1, broodfish were fed a standard diet (ST1) and one enriched with menhaden oil (ER1) over a 355-d period. ER1-influenced egg fatty acid profile, however, did not positively influence egg production. Both diets produced highly viable eggs and larvae but results varied within treatments. In Experiment 2, broodfish were fed either a standard diet (ST2) or one supplemented with oils (ER2) rich in docosahexaenoic and arachidonic acid using a 203-d cycle. Both treatments produced eggs but fertilization rates ranged 0,10%. There was no clear influence of the diets on egg fatty acid profiles. These results indicate that red snapper can spawn spontaneously in tanks under controlled environmental conditions and produce viable eggs and larvae when fed diets based on squid, shrimp, and fish. The fatty acid composition of the diets was reflected in the eggs to some degree, but the oil enrichments did not further enhance the reproductive performance and egg quality under the conditions of this study. [source]

    Growth, Maturation, Induced Spawning, and Production of the First Generation of South American Catfish, Pseudoplatystoma sp., in North America

    Konrad Dabrowski
    Growth, plasma steroids, and the appearance of gonads (histology and gonadosomatic index) were followed in South American catfish (surubim, Pseudoplatystoma sp.) raised in captivity in the aquaculture facility at The Ohio State University, Columbus, Ohio, USA, from 2003 until 2006. Broodstock growth showed a great individual variation and it did not seem sex dependent. The levels of 11-ketotestosterone were high in males during the reproductive season. Three out of six females spawned after receiving two doses of carp pituitary extract (0.5 and 5 mg/kg) at 11-h intervals. Fertilization was performed in only one female in February 2006. Egg size was 0.73 0.06 mm in diameter at stripping. Two males released sperm, and it was used for fertilization. Sperm concentrations were 24 109 and 15.5 109 spermatozoa/mL in Male 1 and Male 2, respectively, and viability was confirmed after activation in 0.3% NaCl. Embryo survival at 9 h after fertilization was 44 and 23% for Male 1 and Male 2, respectively. Embryos hatched 15 h after fertilization. Larvae were 3.53 0.09 mm in length at hatching and were successfully raised (72% survival after 2 wks) using live brine shrimp nauplii. [source]

    Spawning of a Captive Population of California Sheephead, Semicossyphus pulcher

    Dave Jirsa
    This study represents the first detailed description of spawning and patterns of egg production in a captive population of California sheephead. In March 2004, females ranged in size from 369 to 430 mm total length (TL) and weighed 0.8,1.5 kg. Males ranged in size from 475 to 510 mm TL and weighed 1.7,2.3 kg. Spawning began in April and continued daily through September and then sporadically through October. Egg production ranged from 1000 to 375,000 eggs/d, with an average of 130,000 eggs/d. Egg production peaked in May at 222,000 eggs/d and decreased throughout the remainder of the season. Total annual fecundity from this group was 1,942,000 eggs/kg female body weight. Egg viability ranged from 0 to 80% with an average of 50%. Viability showed a general increase at the beginning of the season and a decrease at the end of the season. Eggs were 0.9,1.0 mm in diameter and hatched in approximately 48 h at 18,19 C. Hatch rates showed a general decline throughout the season. This study shows that California sheephead will spawn readily in captivity providing thousands of viable eggs daily and lays the groundwork for culture of this species. [source]

    Progress Toward Year-round Spawning of Southern Flounder Broodstock by Manipulation of Photoperiod and Temperature

    Wade O. Watanabe
    Reliable methods have been developed for controlled spawning of captive southern flounder, Paralichthys lethostigma, broodstock during their natural winter (December,February) spawning season. From 1999 to 2004, we evaluated the effects of manipulation of photoperiod and temperature on both advance and delay spawning to produce viable embryos throughout the year. Wild-caught adult broodstock were held in 4.8- to 7.0-m3 controlled-environment tanks at a sex ratio of approximately 12 females to 4 males. Broodstock were subjected to different artificial photothermal conditioning regimes: extended winter (EW), accelerated (A-10-, A-6-, A-4.5-, and A-3.8-mo regimes), and delayed (D-16- and D-14-mo regimes), with gradual and abrupt transitions, respectively, from long to short daylengths. Under an EW cycle, fish were exposed to constant short daylengths (10 L: 14 D) after the winter solstice in January. Eighty-seven natural spawnings from December to April produced 18.3 106 eggs, with 20.9% hatching successfully (i.e., overall egg viability). Under an A-10-mo cycle, rate of decrease in daylength was accelerated after the summer solstice in July, to reach winter conditions in October. Seven induced spawning trials from October to November produced 897 103 eggs, with 40.4% viability. Under an A-6-mo cycle, rate of change of photoperiod was accelerated after the winter solstice in January, to reach winter conditions in July. Three induced spawning trials in July produced 550 103 eggs, with 14.7% viability. Under an A-4.5-mo cycle, broodstock exposed to EW from January through April were exposed to an accelerated cycle to reach winter conditions by October. Four induced spawning trials from September to November produced 729 103 eggs, with 28.7% viability. Under an A-3.8-mo cycle, broodstock exposed to EW conditions from January through April were exposed to an accelerated cycle to reach winter conditions by September. Five induced spawning trials from September to November produced 510 103 eggs, with 45.9% viability. Under a D-16-mo cycle, fish were exposed to a decelerated decline in photoperiod after the summer solstice in July, to reach winter conditions in May, when atretic females were observed. Under a D-14-mo cycle, fish were exposed to constant summer conditions from December through mid-June and then to an abrupt decline in photoperiod to winter conditions in late June. Six induced spawning trials from September to November produced 763 103 eggs, with 13.0% viability. Production of viable embryos was greatest during the extended winter because of abundant natural spawnings. While successful natural spawnings were rare during the fall or summer, viable embryos were produced through induced spawnings during all seasons of the year, with no significant (P > 0.05) differences in egg viability. Extended winter conditions prolonged spawning from 3 to 5 mo. Accelerated (3.8,10 mo) regimes were effective in producing viable embryos from summer through fall, but a minimum of 5 mo was required to complete gonadal recrudescence. While constant long daylengths after the summer solstice delayed gonadal recrudescence, with spawning obtained 2.5 mo after an abrupt reduction to short daylengths, a decelerated decline in photoperiod did not. Artificial control of daylength enabled precise control of gonadal recrudescence and year-round spawning in southern flounder without adverse effects on the quality of eggs and larvae and will improve availability of seedstock for commercial aquaculturists. [source]

    Sustained, Natural Spawning of Southern Flounder Paralichthys lethostigma Under an Extended Photothermal Regime

    Wade O. Watanabe
    Hormone-induced spawning of southern flounder Paralichthys lethostigma has produced substantial numbers of viable eggs, but wide variations in fertilization and hatch rates have been reported. Recently, sustained natural spawning of southern flounder broodstock, without hormone induction, has been achieved in our laboratory. Adults (average weight = 1.12 kg; N= 25), including 6 captured as juveniles in 1993 and 19 captured as adults during September 1998, were stocked in two 4.8-m3 controlled-environment tanks in October 1998 and held under natural photothermal conditions until January 1999, when an artificial winter photo-period of 10 L:14 D was initiated and then maintained through April 1999. Sex ratio was approximately 13 females:8 males:7 unknown. Natural spawning was observed in early December 1998 and increased in frequency to a peak in March 1999, before declining in late April. Water temperature ranged from 13.9 to 24.5 C during the spawning period. Natural spawnings over 142 d produced a total of 18.3 106 eggs, with a mean fertilization rate of 28.0% (range = 0,100%), yielding 4.94 106 fertilized eggs. The mean percentage of eggs that remained buoyant in full-strength seawater (34 ppt) was 41.3% (0,98%), while hatching rate of buoyant eggs was 37.3% (0,99%) and survival of yolksac larvae to the first-feeding stage was 30.2% (0,100%). Gonadal biopsies in late April identified six females from both tanks as probable spawners. A preliminary comparison suggests that natural spawning produced much larger numbers of viable eggs per female, with higher egg quality (i.e., fertilization and hatching success) than hormone-induced spawning. In contrast to natural spawning, hormone-induced strip-spawning enabled timing of spawnings to be more precisely controlled. These results suggest that a combination of both natural and hormone-induced spawning of photothermally conditioned fish will help produce the large numbers of eggs required to support commercial production. [source]

    Spawning and recruitment patterns of major fish species in Bontanga Reservoir, Ghana, West Africa

    Kwadwo Kwarfo-Apegyah
    Abstract The spawning and recruitment patterns of the major Cichlid fish species, including Hemichromis fasciatus, Oreochromis niloticus, Sarotherodon galilaeus, Tilapia zillii and other species, Auchenoglanis occidentalis, Brycinus nurse, Clarias gariepinus and Marcusenius senegalensis were studied for 24 months in Bontanga Reservoir, Ghana, using length-based fish stock assessment approaches. The species spawned throughout the year, with two spawning pulses described as major and minor spawning seasons. The major spawning season occurred from March to September for the Cichlids, and from May to September for the other species. The minor spawning season, indicative of extended spawning, occurred from October to March for all the fish stocks. Fish spawning began with the onset of the rains in April/May, peaking by June/July, before the rainfall peak in August for all the fish stocks studied. Recruitment was found to occur throughout the year, with major and minor pulses coinciding with the major and minor spawning seasons. Accordingly, the most appropriate time for a possible closed fishing period appears to be from June to August, 1 month after the start of, and before the end of, the rains. The estimated mean standard length (Lm) for first time spawners of A. occidentalis, B. nurse, C. gariepinus and H. faciatus were 11.7, 12.7, 2.7 and 7.5 cm respectively. The estimated maturity,length ratio of 0.4 and 0.2 for O. niloticus, S. galilaeus and T. zillii were lower than the known 0.7 for normal growth, suggesting the tilapias matured faster, and at a smaller size, in the reservoir. Apparent sexual precocity associated with early maturity, year-round spawning and recruitment were some important adaptations found to have sustained the reservoir fisheries, even during high fishing pressures. For conservation and sustainable exploitation of the fisheries, instituting a closed fishing season, mesh size regulations, withdrawal rights and a community-based fishery management system are recommended. [source]

    Spawning and merging of Fourier modes and phase coupling in the cosmological density bispectrum

    Lung-Yih Chiang
    ABSTRACT In the standard picture of cosmological structure formation, initially random-phase fluctuations are amplified by non-linear gravitational instability to produce a final distribution of mass that is highly non-Gaussian and has highly coupled Fourier phases. We use the Zel'dovich approximation in one dimension to elucidate the onset of non-linearity, including mode spawning, merging and coupling. We show that, as gravitational clustering proceeds, Fourier modes are spawned from parent ones, with their phases following a harmonic relationship with the wavenumbers. Spawned modes could also merge, leading to modulation of the amplitudes and phases, which consequently breaks such a harmonic relation. We also use simple toy models to demonstrate that the bispectrum, the Fourier transform of connected three-point correlation functions, measures phase coupling at most at second order only when the special wavenumber,phase harmonic relation holds. Phase information is therefore partly registered in the bispectrum, and it takes a complete hierarchy of polyspectra to characterize fully gravitational non-linearity. [source]

    Reproduction, early development and larviculture of the barber goby, Elacatinus figaro (Sazima, Moura & Rosa 1997)

    Maria Eugenia Meirelles
    Abstract The barber goby, Elacatinus figaro, is a cleaner species of ecological importance and of keen interest to the aquarium trade. Endemic to Brazil, it is a threatened species and so aquaculture is a potential solution for reducing pressure on the natural stocks. This study describes the reproductive behaviour, the embryonic and larval development and the general breeding and rearing conditions. Ten wild fish initiated the formation of breeding pairs 20 days after acclimation to captivity. Spawning started 12 days after the first pair was formed, with one female from each pair spawning from 140 to 700 eggs (n=15 spawnings). The average period of incubation of the eggs was 6.8 days at 25 C. The best hatching rate was 99.5% (n=10 spawnings). Larval rearing used Nannochloropsis oculata with rotifers (Brachionus rotundiformis) as the first food (day 0,25); nauplii and meta-nauplii of Artemia were fed from day 18 until larval metamorphosis with subsequent weaning using commercial marine fish diets. The transformation to juveniles started at around the 30th day post hatch. The best larval survival rate until complete metamorphosis was 30.6% (n=4 larvicultures). After this period, the mortality was insignificant. This study demonstrated that the cultivation of barber goby is feasible. [source]

    Comparative folliculogenesis and spermatogenesis of four teleost fish from a Reservoir in south-eastern Brazil

    ACTA ZOOLOGICA, Issue 4 2010
    Yuri Simes Martins
    Abstract Martins, Y.S., Moura, D.F., Santos, G.B., Rizzo, E. and Bazzoli, N. 2009. Comparative folliculogenesis and spermatogenesis of four teleost fish from a Reservoir in south-eastern Brazil. ,Acta Zoologica (Stockholm). 91: 466,473. This study provides a comparative analysis of gametogenesis of neotropical teleosts Metynnis maculatus, Megalancistrus parananus, Cichla kelberi and Satanoperca pappaterra, through histological, histochemical and histometric techniques. In the ooplasm of C. kelberi and S. pappaterra conspicuous lipid vesicles were observed, which are characteristic of pelagic eggs produced by marine fishes. Perinucleolar oocytes were identified in the testis of S. pappaterra suggesting that this species is protogynous without functional hermaphroditism, an unusual pattern for neotropical fresh-water fishes. The spermatozoa of the studied species have rounded heads, a characteristic of fish that externally fertilise their eggs. The follicular (granulosa) cells of the vitellogenic oocytes from the studied species were cuboidal or columnar, however, in C. kelberi there were columnar follicular cells at the vegetal pole and cuboidal cells at the animal pole. Variations of the histochemical content were detected in the cortical alveoli and follicular cells of vitellogenic oocytes showing differences in the mechanisms to block polyspermy and egg adhesiveness. Larger oocytes were recorded in species which demonstrated parental care behaviour and smaller oocytes were noted in those species with fractioned spawning. [source]

    Relating streamflow characteristics to specialized insectivores in the Tennessee River Valley: a regional approach,

    ECOHYDROLOGY, Issue 4 2008
    Rodney R. Knight
    Abstract Analysis of hydrologic time series and fish community data across the Tennessee River Valley identified three hydrologic metrics essential to habitat suitability and food availability for insectivorous fish communities in streams of the Tennessee River Valley: constancy (flow stability or temporal invariance), frequency of moderate flooding (frequency of habitat disturbance), and rate of streamflow recession. Initial datasets included 1100 fish community sites and 300 streamgages. Reduction of these datasets to sites with coexisting data yielded 33 sites with streamflow and fish community data for analysis. Identification of critical hydrologic metrics was completed using a multivariate correlation procedure that maximizes the rank correlation between the hydrologic metrics and fish community resemblance matrices. Quantile regression was used to define thresholds of potential ranges of insectivore scores for given values of the hydrologic metrics. Increased values of constancy and insectivore scores were positively correlated. Constancy of streamflow maintains wetted perimeter, which is important for providing habitat for fish spawning and increased surface area for invertebrate colonization and reproduction. Site scores for insectivorous fish increased as the frequency of moderate flooding (3 times the median annual streamflow) decreased, suggesting that insectivorous fish communities respond positively to less frequent disturbance and a more stable habitat. Increased streamflow recession rates were associated with decreased insectivore scores. Increased streamflow recession can strand fish in pools and other areas that are disconnected from flowing water and remove invertebrates as food sources that were suspended during high-streamflow events. Copyright 2008 John Wiley & Sons, Ltd. [source]

    Communal spawning of brook and river lampreys (Lampetra planeri and L. fluviatilis) is common in the Oir River (France)

    E. Lasne
    Lasne E, Sabati M-R, Evanno G. Communal spawning of brook and river lampreys (Lampetra planeri and L. fluviatilis) is common in the Oir River (France). Ecology of Freshwater Fish 2010: 19: 323,325. 2010 John Wiley & Sons A/S Abstract,,, The taxonomic status of river Lampreys (Lampetra fluviatilis) and brook lampreys (L. planeri) has been repeatedly questioned due to the high morphological similarity of these species. Here, we report a high frequency (54%) of communal spawning involving both species in the Lampetra redds of a French coastal river. These observations suggest that reproductive isolation between the two species may not be as strong as previously supposed. [source]

    Recruitment of burbot (Lota lota L.) in Lake Erie: an empirical modelling approach

    M. A. Stapanian
    Stapanian MA, Witzel LD, Cook A. Recruitment of burbot (Lota lota L.) in Lake Erie: an empirical modelling approach. Ecology of Freshwater Fish 2010: 19: 326,337. Published 2010. This article is a US Government work and is in the public domain in the USA Abstract,,, World-wide, many burbot Lota lota (L.) populations have been extirpated or are otherwise in need of conservation measures. By contrast, burbot made a dramatic recovery in Lake Erie during 1993,2001 but declined during 2002,2007, due in part to a sharp decrease in recruitment. We used Akaike's Information Criterion to evaluate 129 linear regression models that included all combinations of one to seven ecological indices as predictors of burbot recruitment. Two models were substantially supported by the data: (i) the number of days in which water temperatures were within optimal ranges for burbot spawning and development combined with biomass of yearling and older (YAO) yellow perch Perca flavescens (Mitchill); and (ii) biomass of YAO yellow perch. Warmer winter water temperatures and increases in yellow perch biomass were associated with decreases in burbot recruitment. Continued warm winter water temperatures could result in declines in burbot recruitment, particularly in the southern part of the species' range. [source]

    Relationships between water temperatures and upstream migration, cold water refuge use, and spawning of adult bull trout from the Lostine River, Oregon, USA

    P. J. Howell
    Howell PJ, Dunham JB, Sankovich PM. Relationships between water temperatures and upstream migration, cold water refuge use, and spawning of adult bull trout from the Lostine River, Oregon, USA. Ecology of Freshwater Fish 2010: 19: 96,106. This article is a US Government work and is in the public domain in the USA Abstract,,, Understanding thermal habitat use by migratory fish has been limited by difficulties in matching fish locations with water temperatures. To describe spatial and temporal patterns of thermal habitat use by migratory adult bull trout, Salvelinus confluentus, that spawn in the Lostine River, Oregon, we employed a combination of archival temperature tags, radio tags, and thermographs. We also compared temperatures of the tagged fish to ambient water temperatures to determine if the fish were using thermal refuges. The timing and temperatures at which fish moved upstream from overwintering areas to spawning locations varied considerably among individuals. The annual maximum 7-day average daily maximum (7DADM) temperatures of tagged fish were 16,18 C and potentially as high as 21 C. Maximum 7DADM ambient water temperatures within the range of tagged fish during summer were 18,25 C. However, there was no evidence of the tagged fish using localized cold water refuges. Tagged fish appeared to spawn at 7DADM temperatures of 7,14 C. Maximum 7DADM temperatures of tagged fish and ambient temperatures at the onset of the spawning period in late August were 11,18 C. Water temperatures in most of the upper Lostine River used for spawning and rearing appear to be largely natural since there has been little development, whereas downstream reaches used by migratory bull trout are heavily diverted for irrigation. Although the population effects of these temperatures are unknown, summer temperatures and the higher temperatures observed for spawning fish appear to be at or above the upper range of suitability reported for the species. [source]

    Using motion-sensitive radio tags to record the activity and behavioural patterns of spawning Atlantic salmon

    P. Karppinen
    Abstract,,, In this paper, we describe a method employing motion-sensing radio transmitters for recording and identifying behavioural patterns and activity of Atlantic salmon spawning under natural conditions. Simultaneous video monitoring verified recorded activity patterns originating from behaviours such as fighting, nest digging and quivering. The method described here enables more accurate determination of the timing and location of spawning compared to conventional location tracking. Motion-sensing transmitters can also be applied to monitor other species and types of behaviour, and therefore the use and development of such methods deserves further attention in behavioural studies. [source]

    Lateral movement of common carp (Cyprinus carpio L.) in a large lowland river and floodplain

    M. J. Jones
    Abstract,,, Common carp (Cyprinus carpio L.) are a major freshwater invader and knowledge of their movements is important for planning control efforts. To investigate the movement patterns of common carp, radio-tags were implanted into 46 adult fish; 37 near a large floodplain wetland, the Barmah-Millewa forest, and 9 in the Murray River approximately 175 km upstream. Tagged fish were located every second week between August 1999 and March 2001. Common carp occupied total linear ranges (TLR) between 0.4 and 238 km (mean 30 61 km), with 25 fish (62.5%) occupying a TLR < 10 km. Two fish made large distance movements approximately 650 km downstream. Fish sex, the number of locations, time at large, or tagging location explained little variability (P > 0.05) in TLR. Monthly distance from release varied from 0.04 to 238 km (mean 15 44 km), and was not significantly related to river discharge and water temperature, but 29 of 31 (93.5%) fish tagged at Barmah moved from the Murray River into adjacent floodplain habitats upon flooding. Five fish (12.5%) moved large distances (>127 km) upstream of the Barmah-Millewa forest. Fourteen fish (35%) showed site fidelity to within 20 m and usually occupied one or two home sites. Twenty-six fish (65%) showed site fidelity to within 100 m occupying up to five sites during the study period. Movement patterns of common carp were complex, and individuals exhibited different strategies, which is typical of invasive species. Efforts to control and potentially reduce common carp populations in regulated river-floodplain environments should target key floodplain access points and over-wintering habitats to reduce adult biomass, spawning and recruitment levels. [source]

    Reproductive strategies in small populations: using Atlantic salmon as a case study

    F. Juanes
    Abstract,,, Wild salmonid populations with only a few breeding adults may not exhibit a significant reduction in genetic variability compared with larger populations. Such an observation suggests that effective population sizes are larger than population size estimates based on direct adult counts and/or the mating strategy maximises outbreeding, contributing to increased heterozygosity. In the case of wild Atlantic salmon Salmo salar populations, stratification by age classes and sexes on the spawning grounds avoids inbreeding and increases genetic variability. We studied the breeding composition of four Spanish salmon populations. Over a 7-year period we concluded that the probability of within-cohort mating is very low: females generally reproduce after two sea-winters whereas males reproduce mostly as one sea-winter (grilse) and/or mature parr. Considering different levels of contribution of mature parr to spawning derived from field surveys, we developed a simple model for estimating effective population sizes and found that they doubled with 65% parr contribution expected for rivers at this latitude (43N), and ranged from 100,800 individuals. The effect of between-cohort mating was modelled considering different ranges of differences in allele frequencies between cohorts and resulted in 28,50% increases in heterozygosity when considering a 65% parr contribution. The complex mating strategy of Atlantic salmon contributes to explain the high levels of genetic variability found for small populations of this species. This model can probably be extended to other animal species with mating strategies involving different cohorts. [source]