Life history tactics of southern velvet shrimp Metapenaeopsis palmensis (Crustacea,Decapoda) in the waters off southwestern Taiwan

The southern velvet shrimp, Metapenaeopsis palmensis, a small, tropical r-strategist shrimp, was investigated to test whether its life history tactics are similar to those of penaeid shrimps. In total, 7,832 shrimps were collected in southwestern Taiwan from April 2002 to August 2011. For the first time, we have identified the shrimp as a multiple spawner. This species has a size-segregated distribution, with the newly recruited early juveniles [<6.00 mm carapace length (CL)] living offshore (water depth = 30 m) and the subadults and mature spawning adults (CL ≥9.39 mm) living inshore (water depth = 15–20 m). They spawn from February to June before the rainy season when the water temperature exceeds 25°C. Only the larvae hatched in the late spawning season will successfully recruit in the dry season in September–November when the bottom water salinity is higher than 33.5 psu. The life history tactics of this species are different from those found by various previous studies on penaeid shrimps.     

Spawning, egg development and early ontogenesis in rock cod Patagonotothen ramsayi (Regan, 1913) caught on the Patagonian Shelf and maintained in captivity

Rock cod Patagonotothen ramsayi (Regan, 1913) is one of the most abundant fish of the family Nototheniidae inhabiting the Patagonian Shelf and upper Slope in the southwest Atlantic. Recently, P. ramsayi became an important commercial species around the Falkland Islands with annual catch of 60,000–75,000 t. The present study aimed to reveal previously unknown aspects of reproductive biology of P. ramsayi during the first successful maintenance of adults for more than a year in an aquaculture facility with running seawater. The fish spawned at the end of austral winter. During spawning, males changed their coloration dramatically, occupied artificial shelters on the bottom and showed aggressive territorial behaviour. Egg masses were light-yellow to light-orange irregular spongiform. They were negatively buoyant, but located outside shelters and were ignored by males. Egg diameters varied between 2.1 and 2.3 mm, and the number of eggs per egg mass ranged from 26,800 to 123,400. Embryogenesis lasted 28–32 days. Total lengths of newly hatched larvae ranged from 6.2 to 6.7 mm. The yolk sac feeding period lasted approximately 11 days, during which the larvae showed negative phototaxis. One-month-old larvae attained 8.8–9.0 mm in length. This study confirms that P. ramsayi exhibit the reproductive strategy typical for nototheniid species occupying low-latitude peripheries of their distributional range, characterised by a combination of r-features (small eggs and larvae, high fecundity) and K-features (territorial behaviour and possible nest guarding).     

Age,growth, and reproductive biology of blacktail snapper,Lutjanus fulvus,around the Yaeyama Islands,Okinawa, Japan

Age, growth, and reproductive characteristics of blacktail snapper, Lutjanus fulvus, which is a commercial fish species, were investigated using 322 specimens (40–332 mm in fork length) caught around the Yaeyama Islands, Okinawa, Japan. Spawning season was estimated to be from April to October, and spawning was confirmed around the full moon and the last quarter moon. Age determination using sectioned otoliths revealed that ages ranged from 0 to 34 years and the majority was ≥ 3 years. Parameters of the von Bertalanffy growth function were estimated to be L _∞  = 270 mm, k = 0.40, and t ₀  = ?0.48 years for females, and 257 mm, 0.44, and ?0.42 years for males. Initial growth was rapid during the first 3 years, attaining over 200 mm for both sexes, and then females grew larger than males. Sizes (ages) at the first sexual maturity were 225 mm (4 years) for females and 207 mm (3 years) for males. The wide range of age composition in catch with majority of ≥3 years old implied that the current fishing effort to harvest was not sufficiently large enough to collapse the stock immediately.     

Reproductive biology of the silver pomfret, Pampus argenteus (Euphrasen), in Kuwait waters

The reproductive activities of the silver pomfret, Pampus argenteus (Euphrasen), in Kuwait waters were investigated from March 1996 to February 1998. Observations on the seasonal distribution of maturity stages and variations in seasonal fluctuations in the gonadosomatic index (GSI) confirmed recent findings that the spawning period begins in May. The species has a prolonged spawning period in the females extending from May to August, whereas the males mature in April and ripe specimens were encountered in monthly samples until September. The recruitment pattern confirmed the one breeding season. There are two spawning peaks, the first in May and the second in August. Variations in GSI relative to fish length indicated that females and males are most fecund at about 24.5–26.4 cm and 20.5–22.4 cm length classes, respectively. The males mature earlier than females, at a minimum size of 12.5–14.4 cm, while the females mature at 20.5–22.4 cm. The oocyte diameter‐frequency distribution suggests a serial rhythm of spawning. Fecundity ranged from 28 965 to 455 661 and correlated positively with: (a) standard length (P < 0.006); (b) ovary weight (P < 0.001); and (c) body weight (P < 0.001), and negatively with egg size (P < 0.003).     

The reproductive biology and early development of the African pike,Hepsetus odoe,in the Okavango Delta,Botswana

Synopsis The reproductive biology of the African pike,Hepsetus odoe, was studied over a four-year period in the Okavango Delta, Botswana. Spawning takes place between August and May in different parts of the Delta. Fish in the seasonal swamp and drainage rivers have a truncated spawning season between August and January, while those in the perennial swamp have an extended spawning season from September to May. The variation in spawning season appears to be associated with the degree of environmental perturbation brought about by the annual flood cycle. Male and female pike mature at 140 and 160 mm standard length (SL) respectively. Females predominate in the population and produce an average of 6440 eggs per season and are multiple spawners. The number of eggs per spawning averages about 2630. The eggs are deposited in a foam nest which is guarded by the parents. Newly hatched embryos suspend themselves below the nest via a cement gland and remain in the vicinity of the spawning site until they have reached a relatively advanced stage in their development. The larval period is relatively short which implies that this species undergoes nearly a direct development. Foam nests appear to be a predator avoidance mechanism as well as an adaptation to fluctuating oxygen and water levels. The initiation of the spawning season is more closely associated with water temperature than with the annual flood cycle which appears to be more important in regulating the size of the spawning stock.     

Reproductive biology ofAwaous guamensis, an amphidromous Hawaiian goby

Synopsis Spawning season, size at first reproduction, oocyte maturation, and fecundity ofAwaous guamensis, an amphidromous Hawaiian goby, were studied from June 1989 through May 1991 in the Wainiha River, Kau'ai, Hawai'i. Female fish larger than 73 mm standard length (SL) had mature gonads from August through December in 1989 and 1990. Gonadosomatic index (GSI) values for mature females ranged from 0.2 to 14.5 during the spawning season. Male fish larger than 64 mm SL had elevated GSI values from June 1989 through December 1989 and from August 1990 through December 1990. Mature sperm were found in two male fish collected in January and February. GSI values for mature males ranged from less than 0.01 to 4.0 in the spawning season. Size-frequency distributions of measurements of vitellogenic oocyte diameters and microscopic observations of oocytes indicated this species has group-synchronous oocyte development. Ovarian maturation stages examined over a 29-month period suggest that members of the stock spawned at different times within the spawning season, although mass spawning events have been documented for this species. Estimates of clutch sizes from nests measured in situ were comparable to estimates of potential fecundity from in vitro examination of ovaries, and indicated that female fish deposited an entire clutch during a spawning event. No evidence for multiple spawning by an individual fish in a single season was found. However, microscopic observations of brown bodies in some ovaries suggested that individual fish probably spawn more than once in a lifetime.     

Growth,reproduction, and feeding oF Fundulus heteroclitus (L.) on a North Carolina salt marsh

Fundulus heteroclitus (L.) from a North Carolina Spartina marsh teed largely on small crustaceans (amphipods, tanaids and copepods) and polychaetes. Fish longer than 30 mm standard length also ingested considerable amounts of living plant material. Smaller individuals were distinctly carnivorous. Recognizable particles of Spartina detritus occurred in less than 15% of the guts examined. The relationship of weight to length changed significantly during the year. Although females were larger than males of the same age. males were heavier than females of the same length, except for a brief period at the peak of the spawning season in the early spring. An average second season fish may lay up to 512 eggs from March through August, but first season fish did not reach reproductive size by the end of the spawning season. Growth of first season fish in mid-summer averaged 5% of their total weight per day. These significant seasonal changes in ecological properties of killifish populations are important in any estimates of growth, reproduction, and production.     

Reproductive biology of wahoo, Acanthocybium solandri, off eastern Australia

A dearth of basic biological information for wahoo, Acanthocybium solandri, currently hinders the ability of scientists and managers to assess population sustainability and appropriately manage the dramatically increasing global catch. This study examined the gonads of 382 wahoo collected off eastern Australia during 2008–2011 to quantify their reproductive biology in the region. The overall sex ratio of the sample was 3.2:1 (females:males), however this differed significantly among fishing sectors and areas. The estimated fork length at which 50 % of female wahoo reach maturity was 1,046 mm. Similar to the Atlantic Ocean, female wahoo have a protracted summer spawning season during October-February. The mean spawning frequency of female wahoo was uncertain but may be approximately 2–3 days, with evidence of fish actively spawning on consecutive days. Batch fecundity of females was positively correlated with fish size and estimates ranged between 0.65 and 5.12 million oocytes. Relative fecundity was estimated at 122.0 (±9.7) oocytes per gram of ovary free body weight and did not differ with fish size or throughout the spawning season. Estimation of reproductive parameters such as size- and age-at-maturity may facilitate the construction of per-recruit stock assessments of wahoo in the region.     

Reproductive and feeding biology of the Natal mountain catfish, Amphilius natalensis (Siluriformes: Amphiliidae)

Aspects of the biology of the Natal mountain catfish, Amphilius natalensis, including gametogenesis, spawning season, size-at-maturity, sex ratio, diet and feeding morphology were determined from fish collected in the Songimvelo Game Reserve, South Africa, between 1989 and 1990. Female sexual maturity was established at 63 mm total length. A. natalensis is an asynchronous, iteroparous spawner, breeding throughout summer from August to February. Sex ratio of females to males was 2.2:1, with females attaining a significantly larger size than males. Gametogenesis followed a pattern similar to that of other freshwater teleosts peaking over the spawning period. Stomach content analysis and observations on feeding morphology revealed that A. natalensis was an opportunistic predator with large fish consuming larger prey from a greater variety of taxonomic groups. The most abundant prey items eaten were dipteran (particularly Chironomidae) and ephemeropteran (particularly Baetidae) larvae.     

大凉螈繁殖生态

大凉螈是我国特有的珍稀有尾两栖动物,其种群数量目前呈现明显下降趋势,然而涉及该物种保护的繁殖生态学研究仍十分匮乏。通过融合围栏陷阱及标志重捕的样方调查法,对大凉螈石棉栗子坪种群繁殖个体和变态登陆幼体的迁徙、繁殖群体种群大小、繁殖场内雌雄有效性比变化等进行了研究。运用Jolly-Seber法估测了繁殖种群大小,运用单因素方差分析或Kruskal-Wallis秩和检验比较了不同时期进入繁殖场的雄性大凉螈头体长及体重,运用t检验或者Wilcoxon秩和检验比较了雌雄性间形态上的差异,运用t检验、t′检验或Wilcoxon秩和检验比较了野外抱对雄性与非抱对雄性间的体征差别,运用Pearson相关分析探讨了雌性产卵量与其身体形态的关系,同时观察了卵的孵化情况。研究结果表明:大凉螈的繁殖季为每年的4月下旬到7月下旬,幼体最早于8月上旬变态登陆。估测调查地繁殖场内雄性大凉螈繁殖种群大小约为391尾,雄螈较雌螈更早进入繁殖场且在场内停留时间更长,体重较轻的雄螈较晚迁入繁殖场。有效性比明显偏雄(雌/雄:0.03—0.10)。雌雄间具明显性二型性,雌性个体的头体长、体重及肥满度均大于雄性,而雄性的尾高和尾长占全长的比例则大于雌性。对比自然抱对雄性和非抱对雄性个体发现,抱对个体在头体长、体重和尾高等体征方面显著大于非抱对个体,暗示这些形态特征可能在雄性竞争配偶的过程中起到关键作用。雌螈在室内条件下平均产卵数为176枚,产卵历时2—4 d,产卵量与雌性肥满度正相关,卵的平均孵化期为15.7 d,孵出幼体平均全长为9.74 mm。     

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.     

Growth of dark chub, Zacco temmincki (Cyprinidae), with a discussion of sexual size differences

I examined the annual and seasonal growth of dark chub, Zacco temmincki, in a Japanese river. Investigation of opercular rings showed that the fish reached a maximum age of 8 years. There was no significant sexual size difference at younger ages (3–5 years), but males were larger than females at older ages (6–7 years). Annual increments of length and weight for males that were recaptured were also larger than those for females. The fish spawn from June to August. Females grew for a short period from April to May, but males on average grew for a longer period from April to August. There was no sexual difference in growth rate except during the spawning period. Annual growth rate was negatively correlated with fish length in each sex. The sexual size differences at older ages of the fish might be due to the polygynous mating system in which most mature males could not obtain females and invested for somatic growth in the spawning period, and a short growing season that was overlapped considerably with the spawning period.     

Protogynous hermaphroditism in the parrotfish,Calotomus japonicus

Sexual patterns of the parrotfish,Calotomus japonicus, were studied using fifteen specimens collected in February and April, 1990, near Makurazaki, Kagoshima Prefecture. The males ranged from 265 to 345 mm SL, and were larger than the females on average. Most females ranged from 202 to 260 mm SL, but a female of 305 mm SL was obtained. Sexual dichromatism was conspicuous. Histological examination of the gonads and low values of gonado-somatic indices of both males and females indicated that they were not in spawning season. It was concluded that C.japonicus is a protogynous hermaphrodite, because all male specimens had secondary testes. It was pointed out that the present species has a weak size-sex relationship. Because the specimens examined did not include primary males, it is suggested that primary males are relatively rare, if they occur at all.     

Reproductive biology of the armoured catfish Loricariichthys castaneus (Castelnau, 1855) in Lajes reservoir,southeastern Brazil

Sex ratio, gonadal development, breeding season and fecundity of the armoured catfish Loricariichthys castaneus were described to assess its reproductive strategy in a Brazilian tropical reservoir. In total, 226 specimens (199 females and 27 males) were captured from September 2005 to August 2006 and examined in the laboratory. Females outnumbered males and achieved sizes larger than 330 mm TL. Oocyte development, determined by histological analysis, was asynchronous with oocyte size, ranging from pre‐spawning (27–270 μm) to spawning (243–3460 μm), followed by a sharp decrease in the mean oocyte diameter postspawning (590–730 μm) as the spawning proceeded. Spawning occurred throughout most of the year, peaking in August–September and reaching a low in April–May, according to variations in GSI and frequencies of stages of gonadal development. Batch fecundity ranged from 242 to 833 vitellogenic oocytes (relative fecundity = 2.27 oocytes g^?1), averaging 483 oocytes, and was positively related to gonad weight (P = 0.00003). Oocyte diameters ranged from 0.027 to 5.59 mm, with vitellogenic diameters ranging from 2.08 to 5.59 mm. Continuous development of oocytes throughout the year suggests that L. castaneus presents indeterminate fecundity and is a batch‐spawner. These attributes, associated with parental care and a wide reproductive period, correspond to an equilibrium strategy that has proved to be effective in the Lajes reservoir.     

Reproductive cycle of gilt sardine,Sardinella aurita,Valenciennes 1847, in the eastern middle Adriatic Sea

The annual reproduction cycle of gilt sardine, Sardinella aurita, based on gonad maturity stages, gonad weight and gonadosomatic index was the subject of this study. A total of 2033 gilt sardines (983 males, 1021 females and 29 undetermined) were analysed. Fish were collected monthly from commercial purse seiners between November 2007 and January 2009 in the eastern middle Adriatic Sea (mesh size 8 mm/bar length/; sampling: five boats per month). Based on the monthly evolution of gonad maturation stages, gonad weights and gonadosomatic index, the peak spawning season was determined to be from June to August. Variations in sea surface temperature (SST) coincided with monthly variations of the gonadosomatic index. Highest monthly average values for both analysed parameters were recorded in July (GSI = 3.38; T = 26.5°C). Fifty per cent (L₅₀) of males and females reached sexual maturity at TL 15.8 cm and at 16.6 cm, respectively. Absolute fecundity ranged from 8458 to 48 032 (mean 34 565 ± 10 310), whereas relative fecundity was from 171 to 722 (mean 385 ± 104.35). Mean value of the oocyte size was 0.53 ± 0.10 mm.     

Batch fecundity and spawning frequency of invasive Hemiculter leucisculus (Basilewsky, 1855) in Erhai Lake,China

Hemiculter leucisculus are multiple spawners with indeterminate fecundity, although previous fecundity estimates have assumed a determinate spawning pattern. Batch fecundity and spawning frequency of H. leucisculus were studied in Erhai Lake, China, in which the fish, as an exotic species, has become a successful colonizer. Spawning frequency was 16.05 %, as determined from the percent of females with postovulatory follicles 12 to 36 h old during the peak reproductive period (from May 27 to August 8). The average interval between spawning was 6.2 days and there were more than 16 total spawning batches during the peak reproductive period. The average batch fecundity (mean ± SD) was 11,934?±?5,921 hydrated oocytes in 40 females (standard length or SL: 9.1–14.4 cm), while relative batch fecundity was 560?±?137 eggs g^?1 wet weight. The total potential annual fecundity was approximately 190,944 oocytes over the whole spawning season and was much higher than the estimated standing stock (31,585 oocytes) of yolked oocytes (36 females, SL: 9.5–16.2 cm) at the beginning of the spawning season in April 2010. This high annual fecundity is likely to have contributed to successful invasion of Erhai Lake by H. leucisculus.     

Annual reproductive cycle and growth of the pen shell Atrina maura (Pterioidea: Pinnidae) on sand-bottom culture in the Ensenada Pabellones lagoon system,Gulf of California,Mexico

Abstract

The reproductive cycle and growth of the pen shell, Atrina maura, which was cultured in the Ensenada Pabellones lagoon system, Gulf of California, from March 2008 to March 2009, is described in this article. Histological techniques and the condition index were used to determine its reproductive condition. The sex ratio was 0.57 females:1.72 males within the population studied. There were no differences (χ², p < 0.05) in shell length (SL) between males and females. The mean length of the sampled specimens ranged between 50.99 ± 4.86 mm and 218.16 ± 8.87 mm. The histological results confirmed that A. maura is a gonochoristic organism that presents synchronic development of the gonads. The maturity and spawning phases were observed throughout the study period, with the exception of March and May 2008. The frequency of the gonad development stages obtained per month suggests that this species reproduced two times annually, with one important reproductive period from June to September, a minor reproductive period from November to February, and two resting periods as follows: July to August and January to February 2009.     

Reproductive biology of brown trout, Salmo trutta macrostigma Dumeril 1858, in a tributary of the Ceyhan River which flows into the eastern Mediterranean Sea

The study describes some key elements of the reproductive biology, including spawning season, age at sexual maturity, fecundity and egg diameter of the native brown trout, Salmo trutta macrostigma, in a tributary of the Ceyhan River. A total of 197 brown trout (118 females and 79 males) were captured in 2000–2001 by electric fishing. In observations on monthly changes, the gonadosomatic index (GSI) and the monthly frequency distribution of egg diameter confirmed that spawning lasted from November to January. Some 27.7% of the females and 62.5% of the males attained sexual maturity in their second year. The smallest fork length (FL) of brown trout attaining sexual maturity was 17.4 cm for males and 17.8 cm for females. Mean fecundity in age groups II, III, IV and V were 360, 452, 693 and 1283 eggs per female, respectively. One 9‐year‐old female had a unique 3232 egg count. The mean fecundity of the sampled population was 554 eggs per fish, positively correlated with the FL (mm) (R = 0.8227 ) and body weight (R = 0.8130). The diameter of mature eggs in the spawning season ranged from 3.250 to 5.930 mm, with a 4.146 mm average. Mean egg diameter in age groups II, III, IV and V in the spawning season were 0.813, 3.799, 4.663 and 5.243 mm, respectively. Fecundity, egg weight and diameter were statistically different in all age groups.     

Salinity and spawning of nurseryfish, <Emphasis Type="Italic">Kurtus gulliveri</Emphasis>, in the Adelaide River of northern Australia with notes on electrofishing and photos of a male carrying eggs

Nurseryfish are unique among fishes in that the males carry the fertilized eggs on a supraoccipital hook on their head. In an attempt to learn where, when, and at what salinities spawning occurs, an ichthyoplankton net was towed at 14 stations in the Adelaide River from the mouth (38 ppt) to the most upstream sections of the river (0.1 ppt). Larval nurseryfish (5–27.5 mm SL) were collected, preserved and measured, and water chemistry parameters were recorded with each sample. Larvae were found in the mid-reaches of the river during July–October, most commonly at salinities between 13.6–0.5 ppt. Salinities increased as the dry season progressed. Larvae were not taken at salinities higher than 19 ppt, nor did they occur in the upper-most reaches of the river system during this time of the dry season. What nurseryfish do and where they occur during the massive influx of freshwater runoff during the wet season (November–April) remains a mystery. Electrofishing for nurseryfish proved to be ineffective in the Adelaide River due to its extraordinary turbidity which made recovery of stunned fish difficult and fresh material of males carrying eggs remains elusive. Two historic photographs showing males carrying eggs are described.     

Reproduction of the sandpaper skate,Bathyraja kincaidii (Garman 1908) in the eastern North Pacific

The sandpaper skate, Bathyraja kincaidii, is commonly taken as bycatch in trawl fisheries off central California. The impact of fisheries exploitation on this population is unknown, however little is known about its biology, including its reproductive life history. To determine reproductive aspects of B. kincaidii, 506 individuals were collected from commercial trawls, museum collections, and monthly trawl and longline surveys conducted by the National Marine Fisheries Service. Males ranged from 112 to 635 mm TL, whereas females ranged from 113 to 610 mm TL. Males reach first maturity at 440 mm TL and at ~3 years, whereas females reach first maturity at 450 mm TL, approximately 1 year later. Size and estimated age at 50 % maturity were similar between sexes: 492 mm TL and 7.5 years for males and 467 mm TL and 7.1 years for females. Gonadosomatic index (GSI) and hepatosomatic index (HSI) values indicate a continuous reproductive cycle, with a seasonal peak in the summer and fall, and a resting period following egg case deposition.