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1.
Retusa obtusa held individually in the laboratory carried largeoocytes in the gonad but did not spawn in December-late January.In late Jan-early Feb, however, the first few individuals producedbatches of 817 eggs and, by early February, most individualswere producing means of 24 eggs d1 and maximain late Feb of <7.9 d1. Spawning declined to low levelsin few individuals in late March. By early April, spawning hadvirtually ceased prior to the drastic loss of adults in thepopulation by May. Larger R. obtusa generally produced more eggs than smaller onesand the few specimens shorter than 3.8 mm produced markedlyfewer than those of 3.85.0 mm shell length. Twenty of the 34 R. obtusa held in the main breeding period(4 sets started 29 Jan-3 Mar) spawned in 3 or more successiveweeks whereas only 6 of them failed to spawn in 2 consecutiveweeks, so indicating that several successive batches of eggsare commonly produced. Yet in virtually all individuals (exceptat the start of breeding) more eggs were produced in the firstweek of captivity than subsequently. These first-week valuesimply total production by individuals in the spawning seasonof some 112-305 eggs comprising about 2.8-7.6 mg dry weightor, by the Forth estuary population, of 26880-73200 eggs m2comprising 0.67-1.83 g dry weight m2. (Received 19 August 1988; accepted 30 September 1988) 相似文献
2.
Sanchez-Velaso Laura; Shirasago Bernardo; Cisneros-Mata Miguel Angel; Avalos-Garcia Carlos 《Journal of plankton research》2000,22(8):1611-1618
Sardinops caeruleus larvae were almost absent during the ElNiño 19971998, when the sea surface temperature(SST) increased by 4°C. After the event, these larvae appearedin high abundance between 18 and 22°C SST. Engraulis mordaxlarvae were recorded in high abundance during the El Niño(17 and 25°C SST) and afterwards (14 and 22°C). Duringthe event, they tended to concentrate close to Isla Angel deLa Guarda and Isla Tiburón, the coldest zone. The ElNiño conditions affected the spawning of S.caeruleusmore than E.mordax, with the latter more adapted to strong environmentalchanges. 相似文献
3.
Statolith microstructure was studied in two abundant planktoniccranchiids, Cranchia scabra (56 specimens, 38127 mm mantlelength, ML) and Liocranchia reinhardti (34 specimens, 99205mm ML) sampled in epipelagic waters of the western part of theGulf of Guinea (tropical Atlantic). Growth increments were revealedin ground statoliths of both species. It was possible to distinguishtwo growth zones in statolith microstructure by their colourin reflected light of the microscope: the translucent postnuclearzone and pale white opaque zone. Assuming that growth incrementsin statoliths were produced daily, ages of the largest immatureC.scabra and L.reinhardti were 166 and 146 days, respectively.Both cranchiids are fast-growing squids with growth rates inlength resembling those of juveniles of tropical ommastrephidsand Thysanoteuthis rhombus. Liocranchia reinhardti grows faster:its growth rate in ML is approximately twice that of same-agedC.scabra. The life cycle of both cranchiids consists of twophases. During their epipelagic phase, C.scabra and L.reinhardtifeed and grow rapidly from paralarvae to immature young in theepipelagic waters, attaining 120130 and 170200mm ML by ages of 45 months, respectively. Then they changetheir life style to a deepwater phase. 相似文献
4.
The influence of environmental parameters (temperature, dissolvedoxygen, suspended matter, chlorophyll a) on the condition indicesand gametogenic cycle of the European flat oyster (Ostrea edulisL.) was analyzed in the Mar Menor (Murcia, Spain) between January1990 and December 1992. The highest condition index values wererecorded during the prespawning season at temperatures between1112°C. Condition index values gradually decreasedfrom 14°C, coinciding with the appearance of the first larvaein the plankton. Condition index values were lowest in summer.Multiple regression analysis revealed that the condition indiceswere correlated mainly with temperature and to a lesser extent,with dissolved oxygen, chlorophyll a and suspended matter. Absolutechlorophyll concentrations were low and presented a negativecorrelation with the condition index values, though this correlationwas less pronounced than that of temperature. Gametogenesiswas continuous all year round, but spawning took place onlyat temperatures of 14°C or higher, and larvae were presentin the plankton to 28°C. The low absolute values of chlorophylla and suspended matter found in the oligotrophic Mar Menor didnot seem to affect the gametogenesis, spawning or the larvaldevelopment of the oysters, which feed on picoplankton, principallycomposed of dinoflagellates and bacteria. (Received 29 April 1996; accepted 18 October 1996) 相似文献
5.
The population dynamics of the euphausiids Thysanoessa inermis(Kröyer), T. raschii (M.Sars), and Meganyctiphanes norvegica(M.Sars) have been followed in Balsfjorden in 1976 and 1977.Seasonal variations in length-frequency distributions, growthin carapace length, sex-ratio, and spermatophore productionand attachment are presented and discussed in relation to changesin hydrography and phytoplanlcton standing-crop. An annual generationof T. inermis and T. raschii was spawned in April and May. Eggsand larvae of M. norvegica were not found in Balsfjorden, indicatingthat recruitment occurs from outside the fjord. T. inermis andT. raschii reached maximum carapace lengths of 78 mmand 67 mm respectively and had life-spans of c. 2 years3 months. M. norvegica had a life-span of c. 2 years 6 monthsand reached a maximum carapace length of c. 12.5 mm. In bothT. inermis and T. raschii 0-group underwent the greatest lengthincreases from May to October, I-group from March to Augustand II-group from April to June. The population structure, growthpatterns and growth periods of M. norvegica were difficult todiscern. The phytoplanlcton cycle appears to be the dominantfactor regulating both growth and spawning of the Thysanoessaspp in Balsfjorden, while temperature has no obvious influence. 相似文献
6.
Females of the sac-spawning euphausiid Nyctiphanes simplex Hansenwere incubated under shipboard laboratory conditions to observethe embryonic and larval development time and hatching mechanism.Females ready to spawn have a pale pink ovary that extends fromthe back of the stomach to the first abdominal segment, fillingmost of the haemocoel. This species usually behaves as a totalspawner (produces one batch of oöcytes per cycle of theovary) leaving an empty space in the cephalothoraxwhere the spent ovary is located. After spawning, the youngoöcytes mature and turn pale pink. The eggs do not havea measurable perivitelline space (PVS) in any of the embryonicstages (6.6 x magnification). The embryos hatch as nauplius(8091 h after spawning, 16°C ± 1°C). Theyfurther develop into pseudometanauplii (PMN, 90105 hafter spawning) and metanauplii (MN, 92140 h after spawning)inside the ovigerous sac. The nauplius breaks the thin and fragilechorion by increasing the volume of the body and by using thefirst and second antennae. We call this an expansionhatching mechanism, the fifth distinct hatching mechanism observedso far among euphausiids. N. simplex larvae escape from theovigerous sac late in the MN stage (5 days after spawning),just a few hours before molting into calyptopis 1 (C1) (0.54h). This delayed release extends protection by the female, likelydecreasing the risk of predation or early cannibalism. Additionally,this may save energy by not swimming independently increasingthe time of not return if the calyptopis does not find favorablefeeding conditions. Females are not ready to spawn again untilat least two days after the previous batch of embryos leavesthe ovigerous sac. The interbrood period (IBP) observed rangedbetween 7 and 15 days at 1618°C. This IBP is aboutone-fourth to half than was previously assumed for this speciessuggesting a significant underestimation of the fecundity ofthis species. N. simplex hatching success usually was 100%,except for a few females with all of their embryos dying duringembryonic development. Other females either molted before releasingthe embryos, or the oöcytes were spawned unfertilized (0%hatching success), particularly during winter conditions. Efficienthatching and late free-swimming strategy may partially explainwhy this species is the most abundant neritic euphausiid inthe southern part of the California Current System (CCS) andin the Gulf of California. 相似文献
7.
The diel vertical migration, growth and spawning season of theeuphausiid, Thysanoessa longipes, were investigated using seasonalsamples collected from waters around the Yamato Rise, centralJapan Sea, during the period 1987 to 1999. Thysanoessa longipeswas present throughout a broad bathymetric layer extending downas deep as 1000 m. There was a clear trend for larger specimensto occur at deeper depths. The peak of abundance of the totalpopulation occurred at depths of 30300 m at night, and150500 m during the day, and the distance of the dielvertical migrations of the total population was estimated tobe between 100 and 150 m. Population structure analysis revealedthe occurrence of three cohorts aged 0+, 1+ and 2+ years, withfemales attaining a larger body size than males. Growth as determinedby body length was found to fit well to the von Bertalanffygrowth equation. The estimated life span for males and femalesis 3 years, and females reach maturity in 2 years. Based onthe occurrence of calyptopis larvae, spawning of T. longipeswas estimated to occur over only a limited period of the yearbetween April and May. 相似文献
8.
Ovarian maturation of the pufferTakifugu exascurus (Jordan et Snyder) was induced, and embryonic, larval and juvenile development was observed. The brood fish were collected
in Tassha Bay, Sado Island (38°05′N, 138°15′E), during the spawning season in 1986 which seemed to extend from late June to
mid-July. To each female 3 mg acetone-dried pituitary ofHypophthalmichthys molitrix was injected to induce ovarian maturation, which took place in about 77 hours at a water temperature of 19.5–21.0°C. The
eggs obtained by hormone injection were artificially fertilized with the milt from a collected male. The hatched larvae were
fed successively on rotifersBrachionus plicatilis, Artemia nauplii and minced fish meat, and reared for a period of about one year.
The eggs were spherical, 1.24±0.04mm in diameter, demersal and adhesive. The egg-membrane Was transparent and yolk was orange
in color, containing a cluster of small oil-globules. The incubation period was about 160 hours at a water temperature of
18.5–21.0°C. The newly-hatched larvae, measuring 2.9– 3.1 mm TL, had 8+15 = 23 myomeres. Absorption of the yolk was completed
3 days after hatching, by which time the larvae had attained 3.5–3.6 mm TL. Larval finfolds disappeared and rudimentary dorsal,
anal and caudal fins formed at 4.1–4.4 mm TL, in 6 days after hatching. In 9-day old larva (5.4 mm TL), fin ray rudiments
appeared on the dosai, anal and caudal fins and spine-like scale formed on the belly. In 16-day old specimens, 9.1–10.2 mm
TL, the full complements of fin rays were completed on all the fins and the fish reached the juvenile stage. The growth of
larvae and juveniles reared in 1986–1987 is expressed by the following equations, where y is total length (mm) and x is days
after hatching. y1 = 2.9420· 1.0639x 0 ≦ x ≦ 19 (r = 0.998) y2 = 4.0286· 1.0464x 19≦ x ≦ 33 (r = 0.998) y3 = 9.8854· 1.0180x 33 ≦ x ≦ 72 (r = 0.996) y4 = 20.1555· 1.0080x 72 ≦ x ≦ 115 (r = 0.998) y5 = 28.0610· 1.0049x 115 ≦ x ≦ 202 (r = 0.995) 相似文献
9.
Paralarvae of the family Gonatidae were sampled in the Gulfof Alaska during spring 2001–2003. Taxonomic characterswere determined to allow identification of the specimens tospecies. The dorsal head chromatophore pattern (DHCP) was themost robust character and allowed identification to speciesfor the first time without requiring the removal and examinationof the radula. Six different DHCPs were found among the sixspecies in the study area. The 1140 specimens collected consistedof the following six species: Berryteuthis anonychus (759),Berryteuthis magister (71), Gonatopsis borealis (155), Gonatuskamtschaticus (1), Gonatus madokai (4) and Gonatus onyx (143).The specimens had a size range of 3.0–20.63 mm dorsalmantle length with the majority of specimens smaller than 10 mm.All species showed an increasing trend in abundance from theshelf (0–200 m) to the slope (200–1000 m)to the basin (>1000 m) except G. onyx in 2001 and 2002.Wide variation in distribution and abundance was found for thefour most abundant species; however, in general, B. anonychuswas most abundant and widely distributed, followed by Gonatopisborealis, Gonatus onyx and B. magister. (Received 28 April 2006; accepted 1 February 2007) 相似文献
10.
Age composition and growth rates of the squid Loligo vulgaris(Lamark, 1797) were studied by examination of growth incrementswithin statohths of 419 specimens (mantle length, ML, rangingfrom 32 to 400 mm). The squid were obtained by monthly samplingfrom the catches of commercial trawls off southern Portugalbetween March and September, 1993 The total number of growthincrements in the mounted and ground statohths was counted usinga semi-automatic image analysis system. ML was significantlycorrelated with both the statolith length, TSL and the numberof increments, NI. The female statolith was slightly largerthan the male statolith for the same mantle size. Growth ratesof individuals showed high variability with an average estimatedat 34.6 mm month1 for males and 33.5 mm month1for females. Growth in length between 70 and 280 days was bestdescribed by a power function for both sexes. The growth indexof the statolith (TSL/NI) decreased with individual growth.This result may be related with the onset of sexual maturation.L. vulgaris hatched throughout the year with two distinct peaks,in spring which is the mam breeding period, and in autumn. Thelife cycle of the L. vulgaris population on the south Portugueseshelf was completed in one year
*Present address for correspondence: Instituto de InvestigacionMariflas. Eduardo Cabello. 6 - 36208 VIGO. Spain (Received 28 November 1995; accepted 7 February 1996) 相似文献
11.
Embryonic, larval and juvenile development of the cottid fish,Pseudoblennius percoides were described on the basis of a series of laboratory-reared specimens. The eggs were demersal, adhesive, almost spherical
in shape, measuring 1.66–1.82 mm in diameter, and with numerous various-sized oil globules. Neighboring eggs adhered to each
other to form an egg mass. Hatching occurred between 13 and 16 days after spawning at a water temperature of 15.4 to I6.5°C.
Newly hatched larvae measured from 6.5 to 7.3 mm, averaging 6.9 mm TL, and possessed 40 myomeres. Absorption of the yolk was
completed at about 7.5 mm TL. Flexion of the notochord started and finished at about l0 mm TL and about 14 mm TL, respectively.
Aggregate numbers of all fin rays were completed at over 16 mm TL, when the larvae reached the juvenile stage. The pigment
pattern became the same as that of adults in juveniles longer than 25 mm TL. Lateral lines were completed at over 44 mm TL,
when the juveniles attained to the young stage. The early stages of this species were clearly distinguished from those ofP. cottoides, and the juveniles of fourPseudoblennius species, i.e.P. percoides, P. cottoides, P. marmoratus andP. zonostigma, could be identified mainly by their pigment patterns. 相似文献
12.
Coexisting populations of the mussels, Perna perna and Mytilusgalloprovincialis, were monitored at two sites on the NorthAfrican coast, east of Algiers, over a five year period (19851989).While spatfalls were observed throughout the year, only themajor spring-summer recruitment, which occurred during favourableweather conditions, contributed to the renewal of both musselspecies at both sites. Very high densities (>10, 000 ind.m2) were observed at both sites, but the mussel bedswere composed principally of young and small specimens due toharvesting of the largest animals for use as bait and for humanconsumption. The maximal length observed was 75 mm in P. pernaand 49 mm in M. galloprovincialis. The life span of the specieswas low, 1224 months in P. perna and 1128 monthsin M. galloprovincialis. This survey showed that M. galloprovincialisbecame dominant in both mussel beds due to its resistance todisturbance by human activities. (Received 5 January 1995; accepted 18 April 1995) 相似文献
13.
Statolith morphology and microstructure were studied in twocommon species of panktonic cranchiid squids, Belonella borealis[four juveniles with mantle length (ML) 375450 mm] andGaliteuthis phyllura (13 paralarvae and juveniles, ML 9235mm),caught near the bottom and in pelagic layers over the continentalslope of Siberia in the northwest Bering Sea. The total numberof growth increments within the statoliths ranged from 277 to294 in B.borealis and from 10 to 209 in G.phyllura. Assumingthat these increments were produced daily, both species growrapidly in length (daily growth rate = 1.13mm day1 duringthe first 810 months of their juvenile phase in the mesopelagiclayers, prior to migration into deeper waters for maturation. 相似文献
14.
Vertical distribution of pelagic chaetognaths and feeding of Sagitta enflata in the Central Equatorial Pacific 总被引:1,自引:0,他引:1
The vertical distribution and feeding of pelagic chaetognathsat 5°S, 160°W in the Central Equatorial Pacific wereinvestigated using a series of 0500 m vertical haulswith a VMPS net over a 24 h period between 6 and 7 October 1990.The total number of individuals per haul was between 370 and688. Fourteen species in four genera were found at this station.The most abundant species was Sagitta enflata which comprised32.461.1% of the individuals collected from the 0500m layer. Mesopelagic species made up 9.315.1% of thetotal number of individuals. Sagitta enflata and Pterosagittadraco were found in the upper part of the thermocline both byday and at night. The fraction of the population containingfood items (FCF) of S.enflata in the 050 m layer variedbetween 4.8 and 12.5% (mean 10.8%) and feeding activity washighest between sunrise and noon. The percentages of Copepoda,Foraminifera, crustacean larvae, Chaetognatha, Pteropoda, Ostracoda,fish and unidentified material in the gut of S.enflata were51.9,6.7,3.8,2.9,1.9,1.9 and 30.9%, respectively. Sagitta enflataconsumed food organisms which were mainly between 0.5 and 1.0mm in length. The daily feeding rate of S.enflata was 1.81 preyper individual, which was equivalent to 8.06 mg C m2day1. This corresponded to 相似文献
15.
The diet of Engraulicypris sardella (Cyprinidae) larvae wasdeterinmed from the open waters of Lake Malawi, Africa. Theguts of first-feeding larvae of 23 mm total length (TL)usually contained many cells of 59 µm diametertentatively identified as a non-colonial green alga (Chlorophyta).The number of these cells in the guts of larvae declined aslarvae increased in size, and were not found in larvae greaterthan 9 mm TL. Other types of phytoplankton were rarely seenin the guts of larvae. Copepod nauplii were eaten by larvaegreater than 4 mm TL, and copepodite copepods and cladoceansby larvae greater than 5 mm TL. The biomass of open water crustaceanzooplankton and E.sardella larvae were determined over a 2-yearsampling programme. The mortality rate of E. sardella was negativelycorrelated with zooplankton biomass, but was not significantlycorrelated with the amount of zooplankton food in the guts oflarvae. 相似文献
16.
Fifty-nine specimens of the tropical epipelagic eno-ploteuthidEnoplotcuthis leptura were collected in the central-east Atlanticbetween 19861988. Statoliths were extracted from allspecimens (mantle length (ML) 4.192 mm) and processedunder the statolith ageing technique. The characteristic featureof statolith morphology in E. leptura is a sculpture of therostrum, which is covered by numerous tiny spines and knobs.In the ground statolith it was possible to distinguish fourmain growth zones consisting of narrow growth increments likethose in other squids studied. Allometric growth of statolithsversus ML is negative. E. leptura is a short-lived squid witha half-year life span. Growth rates of E. leptura are high atjuvenile stage (instantaneous rate of growth (G) of body weight(BW) 0.040.06). An early maturation of males (at age4560 days) and females (at 8090 days) causes asharp decrease of somatic growth of E. leptura, and mature squidhave low growth rates (G of BW - 0.OO3-O.0O5). Spawning takesplace between January and September with two peaks: in Januaryand in June-July. (Received 22 November 1992; accepted 15 February 1993) 相似文献
17.
The aim of the study was to describe the peculiarities of pike spawning in mesotrophic Lake Rubikiai, to determine the spawning population structure and evaluate the influence of some environmental factors on year-class strength formation. The data were collected in April and May (1994–2011). A total of 1586 individuals were caught. The age of pike ranged from 1 to 12 years; 2–5-yearold males (96.0%) and 3–8-year-old females (89.1%) prevailed. The overall sex ratio of females to males was 1:4.1. One-year-old spawning males (26.5–28.5 cm) and two-year-old spawning females (31.5–35.5 cm) constituted 2.1% and 2.6%, respectively. Water temperature during the spawning period was relatively stable, between 4 and 6°C, during March and increased slightly towards 10°C in the middle of April. No correlation was observed between female length and spawning date. Year-class strength did not correlate with the last day of ice presence and the minimal water level at the end of spawning (WLmin), but statistically significantly negatively correlated with the maximum water level at the beginning of spawning (WLmax) and the difference between WLmax and WLmin. The mean annual survival rate for pike (aged ≥2) was 0.74 and the mean annual instantaneous mortality rate was 0.45. 相似文献
18.
On a section between Bermuda and Puerto Rico, in March/April 1981 Anguilla sp. larvae abundance and hydrographic conditions were studied. The small larvae (<7 mm Tl) occurred south of 30° N at the subtropical thermal front and showed peak abundance at 26° N. At 23° N larvae of all size groups became less abundant. North-south extention of the spawning area was greater than described in the literature. A considerable net avoidance of the larvae during daylight hauls was observed. Lengths of both Anguilla species increased from the north to the peak abundance area in the south and for A. anguilla also from east to west. Patches with about the fifty fold larvae abundance compared with the surrounding area could be identified. Deeper occurrence of the smallest larvae (Tl = 4 and 5 mm) compared with older larvae, found in earlier studies could be stated. 相似文献
19.
The pearlfish Maurolicus imperatorius occurs above seamounts of the Emperor Seamount Chain between 30°–40° N and 168°–176° E. It forms dense aggregations at the
daytime in the upper mesopelagial above the ground and disperses in the dark period of the day in the surficial layer. Judged
by maturation dynamics of gonads, the spawning of this species occurs from January until April with the maximum in March.
Catches of this species are characterized by expressed seasonal dynamics of size composition. Juveniles appear in catches
in the end of spring-the beginning of summer. The maximum recorded SL is 68 mm. Among large fish, females dominate. The part
of females is maximum in winter and minimum in spring. The age of fish with AC 46–63 mm is 265–420 days. The growth rate is
abruptly retarded at the fourth month of life when the length 40–45 mm is attained. Life duration of most fish does not exceed
1.5 years, though some specimens may attain the age of two years. It is supposed that the presence of another species—M. japonicus—on the Emperor Seamount Chain may result from passive transfer in the Kuroshio waters. 相似文献
20.
Mitsuhiro Takayama 《Ichthyological Research》2002,49(2):165-170
The spawning period of the Far Eastern brook lamprey, Lethenteron reissneri, in the headstream of the Himekawa River is estimated to be between mid-March and late May with the peak of spawning activity
between early April and early May. The sex ratio (female:male) in 1999 ranged from 1 : 2.5 to 1 : 3.0 (mean 1 : 2.8) and in
2000 from 1 : 0.8 to 1 : 4.0 (mean 1 : 2.4). In >90% of the observations of spawning nests, males outnumbered females. The
construction area of spawning nests tended to shift upstream during the spawning period. The nests were constructed at water
depths between 5 and 70 cm, water velocity between 10 and 30 cm/s, and on substrate with pebbles of 5–20 mm in diameter. Lethenteron reissneri constructed nests on substrate similar with Petromyzon marinus, but at shallower points and in areas with a slower water velocity.
Received: April 2, 2001 / Revised: December 12, 2001 / Accepted: December 27, 2001 相似文献