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1.
Synopsis A 16-month study (August 1972 to November 1973) of Sarotherodon mossambicus in the Plover Cove Reservoir, Hong Kong revealed a sex ratio of 1:1 for small fish (below 19 cm standard length), but above this length males predominated in the population. Monthly sex composition also showed this approximately 1:1 ratio except during the months of August and September, when again males predominated. Males and females reached M50 at an average length of 17.8 cm and 16.2 cm respectively. Maturity and gonosomatic index studies showed that spawning occurred from May to October with peaks in June and August, and there were at least two spawnings each year. The relationship between fecundity and standard length of females collected during both spawnings was computed to be F = 118.49L–1150.91. 相似文献
2.
J. Wang F. Liu X. Zhang W.‐X. Cao H.‐Z. Liu X. Gao 《Zeitschrift fur angewandte Ichthyologie》2014,30(2):314-321
This study describes the reproductive biology of the Chinese minnow Hemiculterella sauvagei. The length‐weight relationship, sex ratio, spawning season, size at first maturity, and fecundity were analyzed based on 685 specimens collected from the Chishui River between July 2011 and July 2012. The relationship between standard length (SL) and body weight (BW) were estimated as BW = 2.14 × 10?4 × SL2.801 (R2 = 0.839; N = 413; P < 0.05) for females and BW = 1.31 × 10?4 × SL3.001 (R2 = 0.868; N = 272; P < 0.05) for males. The female to male sex ratio, 1.52 : 1, differed significantly from a 1 : 1 ratio. Females predominated in standard lengths >12 cm. Analyses of the monthly variation in the gonadosomatic index (GSI), the monthly proportions of macroscopic gonadal maturity, and the size distribution of oocytes consistently suggested a prolonged spawning season of H. sauvagei from March to August, with a peak from April to May. Logistic curves describing the relationship between proportion of maturity (Pr) at each length interval and standard length were estimated as Pr = 1/(1 + e26.867–0.306SL) (R2 = 0.999; N = 413; P < 0.05) for females and Pr = 1/(1 + e10.522–0.142SL) (R2 = 0.999; N = 272; P < 0.05) for males. Size at first maturity was estimated as 7.4 cm for males and 8.8 cm SL for females. Absolute fecundity varied from 563 to 5052, with a mean of 2413 ± 874 oocytes per ovary. The relative fecundity was estimated to be 41–299, with a mean of 171 ± 55 oocytes per ovary. The present study provides useful information for fishery management and resources conservation. 相似文献
3.
M. Y. Hossain M. S. Arefin M. S. Mohmud M. I. Hossain M. A. S. Jewel M. M. Rahman F. Ahamed Z. F. Ahmed J. Ohtomi 《Zeitschrift fur angewandte Ichthyologie》2013,29(5):1166-1169
The present study describes the length‐weight relationships (LWRs), length‐length relationships (LLRs), Fulton's condition factor (KF), size at first sexual maturity, spawning season, sex ratio and fecundity of the Morari Aspidoparia morar (Hamilton, 1822) (Cyprinidae). Sampling was done using traditional fishing gear jhaki jal (cast net) from July 2010 to June 2011. Total length (TL), fork length (FL) and standard length (SL) were measured with digital slide calipers. Individual body weight (BW) and gonad weight (GW) were determined to an accuracy of 0.01 g for all specimens. The gonadosomatic index (GSI) was calculated and size at first maturity for males and females estimated using GSI and TL as indicators. Female ≥ size at first maturity was used to determine fecundity. A total of 1200 specimens (males = 552, females = 648) ranging from 4.06–12.84 cm TL and 0.53–16.75 g BW were analyzed. The overall coefficient b for the LWR indicated positive allometric growth (>3.00) in males and isometric growth in females (~ 3.00). ancova (analysis of covariance) revealed significant differences between males and females (P < 0.001). All LLRs were highly correlated (r2 > 0.973, P < 0.001). Sizes at first sexual maturity for males and females were 6.0 and 7.0 cm TL, respectively. KF changed little throughout the year and GSI peaked in November to April, indicating the spawning season (GSImax = 15.0 in females, 2.0 in males). Mature females were dominant during the entire spawning season except in April. Mean total fecundity was 6700 ± 3500, ranging from 1860 to 19680. In addition, relative fecundity ranged from 190 to 1200 (mean 560 ± 235) in the Jamuna River. To ensure sustainable management of this species, the protection of mature individuals during the peak spawning season is highly recommended. 相似文献
4.
The Halicarcinus planatus populations of the southwestern Atlantic Ocean show a highly variable sex ratio and a large size overlapping between females in the last immature instar (ADO) and mature (MAT) females. We hypothesized that these facts are related and that female impregnation has a central role in this relation. Non-impregnated ADO females delay maturity and would continue to grow, leading to size overlapping. This scenario is most probable in populations with a scarcity of males and could affect the growth, maturity and population structure. The sex ratio and female size distribution of several populations of the southwestern Atlantic Ocean were analysed. Growth and maturity were studied in two populations with different sex ratios (Camarones, a population with males, and Rada Tilly, a population where no males were found). Size overlapping was not related to the population sex ratio. Size overlapping was due to a variable moult increment and, to a lesser extent, to delayed maturity. Females mated before terminal moult in both populations. However, in Camarones, physiological maturity was not related to impregnation, while in Rada Tilly, vitellogenic oocytes were observed only in impregnated females. Also, differences in the number of spermatophores in female spermathecae were related to the sex ratio. Our results showed that the morphological maturity pattern of females was not influenced by the population sex ratio. However, physiological maturity was related to female impregnation and sex ratio. Also, the variation in the number of spermatophores suggests differences in the mating system related to the sex ratio. 相似文献
5.
A. Soares de Araújo O. Pedro de Souza W. Silva do Nascimento J. César Sá de Oliveira M. Emília Yamamoto S. Chellappa 《Zeitschrift fur angewandte Ichthyologie》2013,29(6):1259-1263
Several environmental parameters related to the spawning season of the freshwater fish, Psectrogaster rhomboides were identified. The hypothesis predicts synchrony of the spawning season with the rainy period, presenting a seasonal reproductive strategy. This study investigated the total body length and body mass, sex ratio, body size at first sexual maturity, gonadosomatic index, condition factor, fecundity and reproductive period of P. rhomboides in the natural environment. Twelve monthly samplings (mean n = 20) were carried out from March 2009 to February 2010. Fish were captured using 4 cm diameter cast nets and environmental parameters such as rainfall, temperature, dissolved oxygen concentration, pH and electrical conductivity of the water were registered. The sampled population of P. rhomboides (n = 444) showed a sex ratio of 1 : 1. Females attained first sexual maturity at 15 cm total length and males at 15.3 cm total length. Spawning occurred from March to May, with high gonadosomatic index values during the rainy season. This species is a total spawner, with a mean fecundity of 6188 (±367) mature oocytes. P. rhomboides presents a seasonal reproductive strategy, providing a population increase and exploitation of the environmental resources during the rainy period. Rainfall (196.5 ± 4.9 mm) and the concentration of dissolved oxygen (7.82 ± 0.7018 mg L?1) were influential factors during the spawning season. Gonadosomatic index and the condition factor were negatively correlated during the gonadal development cycle of this species. The monthly gonadosomatic index values show that spawning begins when the rainy season is at its maximum and ends synchronously (females r = 0.9171; males r = 0.889) with the end of the rainy season. 相似文献
6.
Nile tilapia Oreochromis niloticus is now the most abundant and commercially important tilapiine in Lake Victoria. From the total of 1 512 fish sampled from commercial gill net fisheries during 2014 and 2015, 809 (54%) were males and 672 (44%) were females, giving an overall sex ratio of 1.20 males: 1.00 females. The mean (± SE) length and weight for all fish were 28.7 (±0.1) cm TL and 506.6 (±7.1) g, respectively. The slope b of the length-weight relationship was 2.98, 3.01 3.01, for males, females, and combined sexes, respectively. The relative condition factor was 1.02 for males and 1.04 for females with little variation across the months of sampling. The length at 50% maturity was estimated as 31.0 cm TL for male Nile tilapia and 26.0 cm TL for females. Sixty percent of the fish in the commercial catches surveyed were below 30 cm TL. Comparisons with earlier studies in this system suggest an overall decline in size at maturity over the past 30 years, which may reflect intense fishing pressure. 相似文献
7.
In this paper we provide life history characteristics for an introduced marbled lungfish (Protopterus aethiopicus) population in Lake Baringo, Kenya, including their length–weight relationship, body condition, fecundity, sex ratio, reproduction and food. These data are compared with those of other populations. Samples were obtained from the commercial fishery between January and October 2001. The lungfish exhibited positive allometric growth, with the length–weight relationship described by the equation: logW = ?6.41 + 3.52 logTL. The mean relative condition factor was close to unity, did not vary much between months and was not significantly different between sexes. The overall sex ratio was skewed in favour of females. The size of fish at first maturity was 70–76 cm total length (TL) for females and 82–88 cm TL for males. Fish in maturity stages III–IV occurred in all monthly samples suggesting year round spawning. The marbled lungfish in Lake Baringo is largely piscivorous and its impact on other fishes certainly warrants further research. 相似文献
8.
Some aspects of the biology and ecology of the gobyKnipowitschia caucasica were studied over a period of 13 months in a poly-to euhaline area in the Evros Delta (North Aegean Sea). This fish grows
rapidly in the summer and autumn after hatching, matures after its first winter, breeds from the end of April to the end of
July, and grows rapidly again in July–September. The older males perish after their second February, whereas some females
have a second breeding season at the end of April/beginning of May, shortly before their death. The fish grows to about 40
mm in total length. There is a positive correlation between the total length (TL) and the standard length (SL) or the cleaned
body weight (CW). SL increases slower than TL, whereas CW increases slower than TL in immature individuals and faster in males
and females. There is no difference between immature individuals, males and females, in the growth rate of SL, TL and CW,
TL. The mean monthly values of the condition factor varies from 0.289 to 0.576 in females and from 0.313 to 0.548 in males.
The overall sex ratio of females to males is 1: 1.46. Fecundity ranges from 60 to 217 eggs with a mean value of 109.8 and
depends upon size, whereas relative fecundity varies between 968 and 2170 with a mean of 1558. The fish feeds predominantly
on benthic amphipods and polychaetes. 相似文献
9.
M. Njiru J. E. Ojuok J. B. Okeyo-Owuor M. Muchiri M. J. Ntiba I. G. Cowx 《African Journal of Ecology》2006,44(1):30-37
The life history characteristics of introduced Nile tilapia (Oreochromis niloticus L.) in Lake Victoria, including, sex ratio, fecundity, reproduction, weight‐length relationship and body condition were studied and compared with those of other populations. Samples were collected by trawling and seining in the Kenyan sector of Lake Victoria between June 1998 and December 2000. Males predominated over females (sex ratio 1.42 : 1 : 00). O. niloticus spawned throughout the year but with a peak between December and June. Length at first maturity was (mean ± SD) 30.81 ± 0.09 for females and 34.5 ± 6 0.48 for males. There was little seasonal variation in relative condition, which ranged from 0.92 to 1.05 in males and 0.94 to 1.07 in females. Gonadosomatic index (GSI) was low during the postspawning period (July to October) and high during the protracted breeding period (December and June). Fecundity ranged from 905 to 7619 oocytes for fish of 28 to 51 cm total length (TL) respectively. The relationships between fecundity (F) and total length (L), weight (W) and ovary weight (OW) were: F = 8.159L1.53, F = 96.269W0.4504, F = 1806 + 39.4OW. The slope b of the weight‐length relationship was 3.08–3.32 for males and 3.07–3.22 for females. Growth was allometric in both cases and was significantly different from the expected value of 3. The life history strategy of O. niloticus is discussed in context of environmental changes occurring in the lake. 相似文献
10.
Ferdous Ahamed Newton Saha Zoarder F. Ahmed Md. Yeamin Hossain Jun Ohtomi 《Zeitschrift fur angewandte Ichthyologie》2018,34(5):1169-1175
The gobioid fish Apocryptes bato (Hamilton, 1822) is a species of mudskipper found in Bangladesh, India, and Myanmar. The reproductive biology of A. bato including sex ratio, size at sexual maturity, breeding season, fecundity, and condition factor was studied in the Payra River, southern Bangladesh during May 2016 to April 2017. A total of 1,028 specimens (303 males and 725 females) were collected. The overall sex ratio was significantly different from the expected value of 1:1 (male: female = 1:2.39, χ2 = 173.23, p < 0.05). Size at sexual maturity was estimated as 4.9 cm standard length. Monthly variations in gonadosomatic index indicate that the main breeding season is from May to December. There was a significant positive correlation of body length and body weight with fecundity. Fulton's condition factor varied in both sexes and was attributed to variations in GSI with maturity. Breeding season was significantly associated with rainfall, but not air temperature. Our findings should improve management and conservation of this fish in the Payra River and surrounding ecosystems. 相似文献
11.
The growth rate, reproductive aspects, and natural mortality of chimaeras and ratfish are poorly known. In this study, life-history
parameters for cockfish Callorhinchus callorhynchus (Holocephali—Callorhinchidae) are estimated, which is an important fish resource exploited in Chile. Specimens were sampled
from the artisanal fishery captures, from November 2006 to November 2007. The standard length (SL) of males fluctuated between
20 and 62 cm, and between 21 and 70 cm for females. Von Bertalanffy growth parameters were estimated through length-frequency
data analysis using MULTIFAN. The length-weight relationship and von Bertalanffy growth parameters were significantly different
for males and females, as well as the length at 50% maturity. For males a model with 5 age-classes was the best, with asymptotic
length L
∞ = 52 cm SL, growth coefficient K = 0.473 yr−1, and age at length zero t
0 = −0.690 yrs. For females the best model was represented by 10 age-classes (L
∞ = 70.3 cm SL, K = 0.193 yr−1, t
0 = −1.158 yrs) in the length-frequency data sets. Length at 50% maturity of males was estimated in 43.7 cm SL, and in 50.2 cm
SL for females. The natural mortality rate fluctuated between 0.42 and 0.82 yr−1 for males and between 0.12 and 0.37 yr−1 for females, depending upon the method used. It is concluded that C. callorhynchus is a species with life-history parameters significantly different between males and females, and such differences should
be taken into account in future population dynamics analysis. 相似文献
12.
Sexual size dimorphism,growth, and maturity of the fluvial eight-barbel loach in the Kako River,Japan 总被引:1,自引:0,他引:1
Shigeru Aoyama 《Ichthyological Research》2007,54(3):268-276
The maturation and growth pattern of the fluvial eight-barbel loach Lefua sp. (Japanese name: nagare-hotoke-dojo), an endangered species, was investigated using an individual identification-recapture
method from 1995 to 1998 in an upper reach of a headwater tributary of the Kako River, Hyogo Prefecture, Japan. Based on observations
of the gonads through the abdominal skin, the loach was estimated to breed mostly from May to July. All the males matured
by age 1+, and all the females matured by age 2+. Gamete release in all individuals of both males and females was predicted from recaptured loaches during each breeding season.
The standard length of mature females was significantly larger than that of males, showing sexual size dimorphism (SSD). The
maximum sizes recorded were 75.4 mm SL for females and 61.2 mm SL for males. Both males and females of immature specimens
grew mainly from May to November, including the breeding season, with no significant differences in growth rates between them.
After sexual maturity, both males and females grew mainly from July to October (or November), after the breeding season, and
the females exhibited higher growth rates than males. Therefore, SSD of the species seems to be attributable to the different
growth rates after maturity. The longevity of the loach was estimated to exceed ten years based on individual growth patterns
of various sizes during the survey period. It is likely that the loach has an iteroparous life history, breeding every year,
and moderate growth rates after maturity. 相似文献
13.
Andres Gongora-Gomez Manuel Garcia-Ulloa Marcial Arellano-Martínez Selene Abad Ana Dominguez 《Invertebrate reproduction & development.》2013,57(1):28-38
AbstractThe 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. 相似文献
14.
Length‐weight relationship and reproductive parameters of Botia dario (Hamilton, 1822) in Assam,India
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The length‐weight relationships, spawning season, sex ratio, size at first maturity and fecundity of Botia dario (Hamilton, 1822), also known as the Bengal loach, were analyzed based on 556 specimens collected from the wetlands of Majuli Island, Assam between June 2012 and May 2013. The sex ratio (M : F) was 1 : 0.68, differing significantly (P < 0.05) from a 1 : 1 ratio. Size at first maturity (Lm50) was estimated as 6.8 cm for males and 7.4 cm for females. Analysis of monthly variations in the gonado‐somatic index (GSI), the monthly proportions of macroscopic gonadal maturity, and the ova diameter suggest a prolonged spawning season of B. dario from May to August, with a peak in July for both males and females (GSI = 15.0 in females; 7.0 in males). Absolute fecundity varied from 2523 to 51 377, with a mean of 18 367 ± 1254 oocytes per ovary. A positive correlation was recorded between total fecundity and body weight (r2 = 0.678). 相似文献
15.
Two laboratory experiments investigated mate guarding and sperm allocation patterns of adult males with virgin females of the snow crab, Chionoecetes opilio, in relation to sex ratio. Although females outnumbered males in treatments, operational sex ratios were male-biased because females mature asynchronously and have a limited period of sexual attractiveness after their maturity molt. Males guarded females significantly longer as the sex ratio increased: the mean time per female was 2.9 d in a 2 males:20 females treatment compared to 5.6 d in a 6 males:20 females treatment. Female injury and mortality scaled positively to sex ratio. Males that guarded for the greatest number of days were significantly larger, and at experiment's end had significantly smaller vasa deferentia, suggesting greater sperm expense, than males that guarded for fewer days. In both experiments, the spermathecal load (SL)--that is, the quantity of ejaculate stored in a female's spermatheca--was independent of molt date, except in the most female-biased treatment, where it was negatively related. The SL increased as the sex ratio increased, mainly because females accumulated more ejaculates. However, similarly sized males had smaller vasa deferentia and passed smaller ejaculates, such that, at a given sex ratio, the mean SL was 55% less in one experiment than in the other. Some females extruded clutches with few or no fertilized eggs, and their median SL (3-4 mg) was one order of magnitude smaller than that of females with well-fertilized clutches (31-50 mg), indicating sperm limitation. Males economized sperm: all females irrespective of sex ratio were inseminated, but to a varying extent submaximally; each ejaculate represented less than 2.5% of male sperm reserves; and no male was fully exhausted of sperm. Sperm economy is predicted by sperm competition theory for species like snow crab in which polyandry exists, mechanisms of last-male sperm precedence are effective, and the probability that one male fertilizes a female's lifetime production of eggs is small. 相似文献
16.
17.
Gonadosomatic index‐based size at first sexual maturity of male and female Amblygaster clupeoides (Bleeker, 1849) (Clupeidae) on the east coast of the Malaysian peninsular
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M. M. Rahman 《Zeitschrift fur angewandte Ichthyologie》2017,33(3):579-582
Size at first sexual maturity and condition of Amblygaster clupeoides were determined in a population at the Malaysian east coast. A total of 887 specimens were collected from commercial fishing vessels between March and November 2012. A random sample was taken each time to avoid bias in the cohort sampling. Size at first sexual maturity was determined by the relationship between the total length and gonadosomatic index (GSI). Similarly, the relationship between the condition factor and GSI was applied to determine the condition at first sexual maturity. The sex ratio was close to 1:1. The total length at first sexual maturity of both males and females were at around 18 cm. Males with a GSI of ≥3.2% and females with a GSI of ≥6.5% were mature, having condition factors of ≥0.90 and ≥0.93, respectively. Based on these results the minimum permissible capture size was identified. This study establishes a strong need for regular and continued monitoring of the changes in fish size at first sexual maturity. 相似文献
18.
Analyses of morphometric parameters of the black pomfret, Parastromateus niger, in the Kuwaiti waters of the Arabian Gulf during a 44‐month study revealed the following length‐length relationships: TL (cm) = 0.63 + 1.15SL (females), TL (cm) = 0.94 + 1.14SL (males) and TL (cm) = 0.75 + 1.15SL (both sexes including juveniles). The 95% CI of the exponent in length‐weight relationship varied from 2.788 to 2.796 in females, 2.726 to 2.732 in males, 2.779 to 2.784 for both sexes and 2.590 to 2.613 in juveniles, all indicating an allometric relationship. Simultaneous analysis of Fulton’s condition factor (K) and GSI indicate that spawning in black pomfret peaks in May and June even though the fish remain in good condition throughout the spawning season. The Fulton’s condition factor was statistically discriminatory in determining the well‐being of P. niger. Variation in average maximum condition was significant between sexes and also higher in 2004 as compared to 2005. The mean size at first sexual maturity (SL50%) was 17.5 cm for males and 29 cm for females. Fecundity ranged from 71 305 to 3 895 449 eggs and correlated positively with: (a) ovary‐free body weight (P < 0.05), standard length (P < 0.05) and ovary weight (P < 0.05), and negatively with egg size (P > 0.05). Fecundity‐total length relationship was best described by the logarithmic equation of the form F = 0.898 + 3.15 × TL3.15. The use of results of such morphometric studies in the management of the P. niger species in the Arabian Gulf is suggested due to its growing commercial importance. 相似文献
19.
Growth and life history traits of Aegean chub,Squalius fellowesii (Günther, 1868) in streams in Muğla Province,Aegean coast,Turkey
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To aid in species' conservation, the aim of this study was to provide initial findings on age, growth and reproduction of an endemic species, Aegean chub Squalius fellowesii (Günther, 1868) populations from streams in the Aegean region of Mu?la Province, Turkey. The species is relatively short‐lived (maximum 6 years), attaining a size of about 200 mm total length with a rapid growth to first maturity (≈60 mm TL), and relatively little growth thereafter. The male:female ratio was 1.0 : 0.6, males significantly outnumbering females in the majority of the streams. General condition values of individual fish varied between 2.9 and 3.4. Sexual maturity was usually achieved later and at larger sizes in females than in males. Sexual maturation in most populations was at the age of 2 years in females and 1 year in males. The species spawns between early April and late May. Mean absolute and relative fecundity were about 4440 eggs and 57 eggs·g?1, respectively. Mean egg diameter was 1.00 ± 0.03 mm, ranging from 0.70 to 1.20 mm. Suggestions for the conservation of Aegean chub are discussed. 相似文献
20.
J. G. Pajuelo J. M. Lorenzo R. Domínguez-Seoane 《Zeitschrift fur angewandte Ichthyologie》2008,24(1):68-76
Diplodus puntazzo is a species characterized by a rudimentary hermaphroditism, with a low level of protandry. The study found that the overall sex ratio was one male to 2.03 females, diverging significantly from 1 : 1, and that there was a ratio of one male to 0.11 transitional fish. The sex ratio varied with season: during the reproductive period the ratio was 1 : 1.86 (male : female), significantly lower than in the non‐reproductive period in which the sex ratio was approximately 1 : 2.26. Both sexes had similar size distributions; however, females were predominant in all size intervals, especially in the larger ones. No significant difference in mean total length (TL) between females (330 mm), males (319 mm) or transitionals (321 mm) was found. The smallest functional female and male analysed were 159 and 157 mm TL, and the largest were 520 and 510 mm TL, respectively. No significant difference in length at first level of maturity, attained at the second year of life, was found between males (281 mm) and females (292 mm), respectively. A protracted spawning season was identified for the species: from September to February, with a peak in November. GSI values followed the same pattern for males and females, with values of females being similar to those of males; the highest values occurred between September and December, with a maximum in November. Occurrence of transitional fish was significantly higher during the month with highest values of GSI than in the resting period. The study found that vitellogenesis did not begin synchronously for all females, and the simultaneous presence of oocytes in all stages of development indicated an asynchronous mode of ovarian development. The presence of postovulatory, together with tertiary yolk vesicle oocytes, indicated that the species is a multiple spawner. 相似文献