Gonadosomatic index‐based size at first sexual maturity of the catfish Eutropiichthys vacha (Hamilton, 1822) in the Ganges River (NW Bangladesh)

This study describes the size at first sexual maturity, length–weight relationships (LWR) in relation to size at first sexual maturity, and Fulton’s condition factor (K_F) of Eutropiichthys vacha in the Ganges River, northwestern Bangladesh. Sampling was done using traditional fishing gear including cast nets, square lift nets and conical traps during January and April, and July to December 2010. For each individual, total length (TL) was measured to the nearest 0.01 cm, and total weight (BW) was determined to the nearest 0.01 g. The gonadosomatic index (GSI) was calculated by the equation, GSI (%) = (Gonad weight in g/BW) × 100. The size at first sexual maturity of males and females was estimated by the relationship between gonadosomatic index and total length. A total of 583 specimens (289 males; 294 females) ranging from 8.30 to 27.00 cm TL and 3.16 to 159.50 g BW were analyzed. Sizes at first sexual maturity for male and female E. vacha were 13.15 and 14.00 cm TL, respectively. The analysis of covariance (ancova ) revealed significant differences in slope and intercept between early and late phases for males (F = 4.532, P < 0.001) and females (F = 21.984, P < 0.001). The K_F was not significantly correlated with TL for males (r_s = 0.052; P = 0.378), but was highly correlated for females (r_s = ?0.165; P = 0.005). This study establishes a strong base for monitoring changes in length at first sexual maturity attributable to high fishing pressures or other reasons within the Ganges and associated river ecosystems.     

Gonadosomatic index‐based size at first sexual maturity and fecundity indices of the Indian River shad Gudusia chapra (Clupeidae) in the Ganges River (NW Bangladesh)

The present study aims to estimate the size at first sexual maturity and fecundity for female Gudusia chapra from the lower Ganges River, northwestern Bangladesh. A total of 250 female specimens, 3.60–13.70 cm in standard length (SL) and 1.00–43.60 g in body weight (BW), were collected during March–August 2006. The gonadosomatic index (GSI) for females was calculated by the equation, GSI (%) = (GW/BW) × 100. The size at first sexual maturity of females was estimated by the relationship between their gonadosomatic index and standard length. The specimen larger (≥8.00 cm in SL) than first size at sexual maturity was used for the estimation of fecundity. The size at first sexual maturity for female G. chapra was considered to be 8.00 cm SL in the Ganges River. The mean total fecundity was 20200 ± 6500 and ranged from 10800 to 36200. This study should be useful for fisheries biologists/managers to impose adequate regulations for sustainable‐fishery management in the Ganges River and elsewhere in Bangladesh.     

Length‐weight relationships,condition factor,gonadosomatic index‐based size at first sexual maturity,spawning season and fecundity of Aspidoparia morar (Cyprinidae) in the Jamuna River (Brahmaputra River distributary), northern Bangladesh

The present study describes the length‐weight relationships (LWRs), length‐length relationships (LLRs), Fulton's condition factor (K_F), 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. K_F 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.     

Notes on the biology of Cancer bellianus (Brachyura, Cancridae) around the Canary Islands

Information on biometric and biological parameters of Cancer bellianus Johnson, 1861 (Crustacea, Decapoda, Brachyura, Cancridae) off the Canary Islands is given. Crabs examined were collected during experimental fishing surveys during 1974–1998. Carapace length, carapace width, total wet weight, sex and ovigerous condition were determined. This species was caught at depths from 153 to 750 m, the deepest ever recorded. Size frequency distributions were assembled and size-weight relationships were estimated by sex. Sex-ratio as a function of size and depth was determined. The size at first maturity was calculated by analysing the relative growth between the carapace length and the left chela width: 103.5 mm CL in males, 101.2 mm CL in females. Ovigerous females, egg size and fecundity estimates are reported apparently for the first time.     

Size at the onset of sexual maturity in the anomuran crab, Aegla uruguayana (Aeglidae)

The size at maturity was studied in the crab Aegla uruguayana from the Areco River (31°14′ S, 59°28′ W), Argentina. Size at sexual maturity was determined according to three criteria: morphometric (change in the relative growth of reproductive characters), histological (first maturation of gonads) and functional (capability to mate and carry eggs). Regarding females, morphometric maturity occurred at a carapace length (CL) of 11.50 mm, considering abdomen width as a reproductive character. Gonad maturity of females could be observed at a minimum size ranging from 15 to 17 mm CL. The smallest ovigerous female observed in the field was 15.60 mm CL, although a relevant population incidence of ovigerous females (86.6%) has just been observed at values higher than 17 mm CL. As for males, the relative growth of the left chela length changed at a value of 15.40 mm CL, while morphological changes in sexual tube occurred between CL of 14 and 16 mm. Testicular maturation occurred at a CL ranging from 17 to 19 mm. The smallest size of males having spermatozoids in their vasa deferentia was 18.70 mm CL. The results obtained indicated that, in both sexes, functional maturity occurred after morphometric maturity and at a size similar to that of gonad maturity. Comparing sexes, females acquired sexual maturity (morphometric, gonad and functional maturity) at sizes statistically smaller than those of males.     

Reproductive biology of Apocryptes bato (Gobiidae) in the Payra River,southern Bangladesh

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.     

Size at first sexual maturity,fecundity, length–weight and length–length relationships of Puntius sophore (Cyprinidae) in Bangladeshi waters

The present study describes the size at first sexual maturity, fecundity, length–weight (LWRs) and length–length relationships (LLRs) of the pool barb, Puntius sophore, using data obtained from different geographical locations in Bangladesh. A total of 905 specimens were caught by traditional fishing gear from March 2010 to February 2011. Additionally, a total of 121 females were collected from a commercial catch of the Padma River during June–July 2011 to estimate size at first maturity and to determine fecundity. Total length (TL), fork length (FL) and standard length (SL) were measured with digital slide calipers. Individual body weights (BW) were determined for all specimens, and gonad weights (GW) from 121 females were weighed to an accuracy of 0.001 g. The female gonadosomatic index (GSI) was calculated as [GSI (%) = (GW/BW) × 100]. Female size at first maturity was estimated using GSI and TL as indicators, and estimated as 5.00 cm TL in the Padma River. Specimens larger than 5.00 cm TL were used to determine fecundity. Mean total fecundity was 5300 ± 2700, ranging from 1580 to 16590. A positive exponential correlation was recorded between total fecundity and total length (r² = 0.421). Relative fecundity ranged from 466 to 4036 (mean 1100 ± 580) in the Padma River. The LWR of pooled data for sexes combined was estimated as BW = 0.0155 TL^2.98 as ancova revealed no significant differences in LWRs between rivers (P > 0.05). All LLRs were highly correlated (r² > 0.983; P < 0.001), and ancova analyses further indicated that LLRs did not differ between rivers (P > 0.05). These results will help in further studies on the population assessment of the species.     

Sex-ratio,seasonality and long-term variation in maturation and spawning of the brown shrimp <Emphasis Type="Italic">Crangon crangon</Emphasis> (L.) in the German Bight (North Sea)

Aspects of the reproductive and maturation biology of the brown shrimp Crangon crangon (L.) were studied in various subareas of the German Bight (North Sea). The size-specific sex ratio of C. crangon was examined based on length frequency distribution data. The sex ratio for the smallest size groups at which sex was determined was typically around 0.5, indicating an even ratio between males and females. The proportion of females decreased in the 30–45 mm size range. In length classes larger than 50 mm, the proportion of females constantly increases to 100% at around 60 mm total length. We concluded that sex reversal from male to female may not occur in C. crangon. Size at sexual maturity was determined from the proportion of ovigerous females. Size at maturity (L ₅₀) was estimated as 55.4 and 62.0 mm total length for spring and winter data, respectively. The seasonal spawning cycle was studied over the period 1958–2005. Between mid February and late June and for size classes larger than 65 mm ovigerous shrimps exceeded 80% and reached up to 100% of the females in the population. This period can be seen as the core spawning season. From early August to early December the proportion of ovigerous shrimps in the female population is very low. Interannual differences in the seasonal process are obvious with a dramatic decline in C. crangon reproductive success in the late 1980s. Various options are discussed for the reasons of the decline and recovery of the reproductive performance.     

Length–weight and length–length relationships,gonadosomatic indices and size at first maturity of Eugerres mexicanus (Steindachner, 1863) (Percoidei: Gerreidae) from the Usumacinta River,Mexico

This study examines the length‐weight (L‐W) and length‐length (L‐L) relationships, gonadosomatic indices, and size at sexual maturity for individuals of the endemic Mexican mojarra, Eugerres mexicanus (Steindachner, 1863) from the Usumacinta River Basin, Tabasco, Mexico. From April 2008 to January 2010, 360 specimens were examined, including 151 (41.9%) male, 179 (49.7%) female and 30 unsexed (8.3%) individuals. Overall female:male ratio was 1.2 : 1. Gonadosomatic index (GSI) values indicate increased reproductive activity during February, with significant differences between males (GSI = 2.07) and females (GSI = 5.48). The mean size at first maturity (L₅₀) was 17.3 cm TL for males and 20.5 cm TL for females.     

Age and size at sexual maturity for the winter skate, <Emphasis Type="Italic">Leucoraja ocellata</Emphasis>, in the western Gulf of Maine based on morphological,histological and steroid hormone analyses

Synopsis We determined age and size at sexual maturity in male and female winter skates, Leucoraja ocellata, from the western Gulf of Maine. Age estimated from vertebral band counts resulted in an Index of Average Percent Error (IAPE) of 5.6%, suggesting that this method represents an accurate approach to the age assessment of L. ocellata. Size at sexual maturity was assessed by evaluating three endpoints: steroid hormone concentrations, and morphological and histological criteria. Our results suggest that 50% maturity in males occurs at a total length of 730 mm and at 11 years of age. For females, our results suggest that 50% maturity occurs at a total length of 760 mm and between 11 and 12 years of age. Collectively, our study suggests that analyzing a combination of reproductive parameters offers an accurate estimation of sexual maturity in the winter skate. Moreover, our results indicate that L. ocellata is a late-maturing and long-lived species, characteristics which make it highly susceptible to over-exploitation by commercial fisheries.     

Relative Growth and Sexual Maturity of the Hermit Crab Paguristes erythrops (Anomura, Diogenidae) from South Atlantic

Some morphometric relationships were studied in the hermit crab Paguristes erythrops to describe its relative growth and the size at which sexual maturity is reached, as well as the shell influence on this process. Individuals were collected monthly from January to December/1999, by SCUBA diving and 12 different characters were measured on males and females. Sexual size dimorphism was observed in length and width of left cheliped. Size at sexual maturity was estimated between 2.8 and 3.5 mm shield length based on the left cheliped relations of the males and on the endopod and exopod of the second pleopod of the females. Differences in the allometry of individuals occupying different shell species were observed. The present work demonstrated the importance of characterizing the type of growth of some parts (pleopods) not yet used in other studies on relative growth of hermit crabs that may correspond to indicators of the size at sexual maturity.     

Sex ratios,sexual maturity,fecundity, and spawning seasonality of Metapenaeus dobsoni off the western coastal waters of Sri Lanka

The reproductive biology of Metapenaeus dobsoni, the most abundant species caught in coastal trawls off Sri Lanka, was studied from samples collected from two main fishing grounds during January 2009 to April 2010. This information is important for developing scientifically sound management measures, as current management is based only on artisanal knowledge. Data obtained included sex ratios, fecundity, gonadosomatic index (%GSI), and morphometric characters with respect to maturity. Size at 50% sexual maturity (L _50m) and size at 50% insemination (L _50in) were estimated for females. In males, L _50m was determined based on the presence of spermatophores in the terminal ampoule. Synchronous seasonal gametogenesis with some asynchrony among individuals was found. Impregnated females were found throughout the year. The GSI and histological examination suggested a prolonged spawning season in M. dobsoni, reaching peaks in August–January and March. Sex ratio, defined as the proportion of females to the total, increased steadily in size beyond 2.35?cm carapace length (CL) and reached 100% at sizes >3.8?cm CL. Estimated population parameters of the species will be important for the sustainable management of this resource.     

Annual reproductive cycle,spawning periodicity and sexual maturity of blue runner Caranx crysos (Pisces,Carangidae) from the Gulf of Gabes (Tunisia,Eastern Mediterranean)

From June 2004 to May 2006, the reproductive biology of the blue runner Caranx crysos was studied in the Gulf of Gabes (Southern Tunisia). Of 1668 individuals examined, 777 were females (46.6%) and 891 were males (53.4%). The sex ratio significantly deviated in favour of males (♀:♂ = 0.87 : 1). The difference in the numbers of females and males was significant among size‐classes. However, there was no significant difference between sexes over months and seasons. Monthly changes in the Gonado‐Somatic Index (GSI) showed a rapid increase during summer to very high levels in July (3.51% for males and 2.55% for females) and August (3.47% for males and 2.59% for females) before declining sharply in September (0.58% for females and 0.38% for males). The gametogenesis activity began with a pre‐maturation phase, from 20 May to the first 10 days of July, followed by a pre‐spawning phase, from 20 July to 20 August. From the last 10 days of August to 20 September the gonads were in the ripe and spawning stages. From the end of September to early May, gonads were in the post‐spawning and resting stages. The size at which 50% of the population reached sexual maturity was significantly different in males and females: males attained sexual maturity at fork length FL₅₀ = 210.20, whereas females attained maturity at FL₅₀ = 222.3 mm. Age at maturity was 2.4 years for males and 2.8 years for females.     

Reproduction in Bagre marinus (Ariidae) off Pernambuco, northeastern Brazil

Throughout 1997, the catches of artisanal gillnetters working off the coast of northeastern Brazil were sampled monthly for Bagre marinus (Mitchill 1815). Significantly more females (n = 207) than males (n = 82) were caught, although there was no significant difference in their size compositions (21–47 cm fork length, FL). All males sampled (21–40 cm FL) had developed gonads and were classified as sexually mature. According to macroscopic and microscopic examination of their reproductive tract, females were separated into four reproductive stages (immature, maturing, mature, and resting). Size at 50% sexual maturity for females was estimated to be 33 cm FL. A positive linear relationship was detected between the size of mature females and their fecundity (between 11 and 32 oocytes). Clear reproductive progress indicated a spawning period between March and May. We conclude that further fishery‐independent data are required to determine patterns of male abundances and distributions.     

Reproductive biology of the fanray, <Emphasis Type="Italic">Platyrhina sinensis</Emphasis> (Batoidea: Platyrhinidae) in Ariake Bay,Japan

The reproductive biology of the fanray, Platyrhina sinensis, was examined in Ariake Bay, Japan, from May 2002 until December 2006. Females reached sexual maturity at a larger size than males [total length (TL) at 50% sexual maturity: male, 393 mm; female, 421 mm]. The present data support a distinct annual reproductive cycle for P. sinensis. The gonadosomatic index (GSI) for mature males showed a clear seasonal trend, declining from August to November. Histological observations showed that mature sperm in the testes occurred from August to November when monthly GSI declined. Concomitantly, pre-ovulatory ova were observed in females collected from August to November. These data indicate that mating, ovulation and fertilization occurred from August to November. Near-term embryos, neonates and recent post-partum females also occurred from August to November. Additionally, all post-partum females possessed large pre-ovulatory ova. Parturition occurred from August to November followed immediately by mating, ovulation and fertilization. Mature females become pregnant every year, and the gestation period is almost 1 year. Fertilized uterine eggs without macroscopic embryonic development were present throughout the annual reproductive cycle, indicating that P. sinensis utilizes embryonic diapause as its reproductive strategy. Both reproductive tracts of females were functional, and fecundity ranged from 1 to 12 with a mean of 6.0, increasing with TL.     

Probabilistic reaction norm reveals family-related variation in the association between size,condition, and sexual maturation onset in Atlantic salmon (Salmo salar)

This study investigated the relationship between the size, condition, year class, family, and sexual maturity of Atlantic salmon (Salmo salar) using data collected in an aquaculture selective breeding programme. Males that were sexually mature at 2 years of age (maiden spawn) have, on average, greater fork length and condition factor (K) at 1 year of age than their immature counterparts. For every 10-mm increase in fork length or 0.1 increase in K at 1 year of age, the odds of sexual maturity at 2 years of age increased by 1.48 or 1.22 times, respectively. Females that were sexually mature at 3 years of age (maiden spawn) have, on average, greater fork length and K at 2 years of age than their immature counterparts. For every 10-mm increase in fork length or 0.1 increase in K at 2 years of age, the odds of sexual maturity at 3 years of age increased by 1.06 or 1.44 times, respectively. The family explained 34.93% of the variation in sexual maturity among 2-year-old males that was not attributable to the average effects of fork length and K at 1 year of age and year class. The proportion of variation in sexual maturity among 3-year-old females explained by the family could not be investigated. These findings suggest that the onset of sexual maturation in Atlantic salmon is conditional on performance (with respect to energy availability) surpassing a threshold, the magnitude of which can vary between families and is determined by a genetic component. This could support the application of genetic selection to promote or inhibit the onset of sexual maturation in farmed stocks.     

Reproductive biology of the guitarfish <Emphasis Type="Italic">Rhinobatos hynnicephalus</Emphasis> (Batoidea: Rhinobatidae) in Ariake Bay,Japan

Size at sexual maturity, reproductive cycle, and fecundity of the guitarfish, Rhinobatos hynnicephalus, were examined in Ariake Bay, Japan. Females reached sexual maturity at a larger size than males [total length (TL) at 50% sexual maturity: males, 431 mm; females, 476 mm]. Monthly gonadosomatic indices of males decreased abruptly from July to August. Histological examinations confirmed the presence of mature spermatozoa in the testes in July, with semen in seminal vesicles in July and August. Preovulatory ova were observed in females with near-term embryos in August. Parturition occurred in August, immediately followed by mating, ovulation, and fertilization. Gestation period is approximately 1 year. Fertilized uterine eggs without embryonic development were present throughout the annual reproductive cycle. Embryonic development began in June and ended in August, indicating that R. hynnicephalus undergoes embryonic diapause (9 months). Fecundity increased with TL and ranged from 1 to 9 (mean, 4.4) embryos per litter.     

Reproductive characteristics of Spondyliosoma cantharus (Linnaeus, 1758) in the Gulf of Tunis

The reproductive features of Spondyliosoma cantharus were studied in the Gulf of Tunis to contribute to better fisheries management on a regional scale and to broaden knowledge on whether there are actual performance differences compared to others areas. A total of 369 fish were caught by trammel and gill nets in the Gulf of Tunis from January 2005 to June 2006. Sex‐ratio, gonad maturation, size and age at maturity, sexual cycle, condition and reproductive strategy were determined. The male : female ratio was initially skewed in favour of females, with males predominating in larger sizes. Length of females at first maturity was 17.8 cm TL (n = 141), which corresponds to 4 years of age. A recommendation is made to increase the length at capture. Spawning season extends from January to May, with a peak in March–April correlated to the lowest sea surface temperatures (14.8–15.6°C); during this period, a dichromatism arises between males and females. The hepatosomatic index and the condition factor present significant monthly changes in relation to the breeding activity. The bimodal size frequency distribution, the biased sex ratio, and the presence of bisexual gonads outline a protogynous hermaphroditism; diandry should be confirmed.     

Length–length relationship, length–weight relationship, gonadosomatic index, condition factor, size at maturity and fecundity of Parastromateus niger (Carangidae) in Kuwaiti waters

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 (SL_50%) 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 × TL^3.15. 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.     

Reproductive biology of the swell shark Cephaloscyllium ventriosum (Carcharhiniformes: Scyliorhinidae)

The Cephaloscyllium ventriosum shark is present in the artisanal fisheries of elasmobranchs on the western coast of Baja California Sur, Mexico. The main characteristics of the sexual maturation of this species based on individuals captured from off north-west Mexico in 2013–2016 are described. The size at maturity of this species was determined for the first time (total length 82 cm for females and 76 cm for males). Most females had one egg case per one uterus, and two per one uterus was an isolated event of low incidence. From the histological analysis of females, it was possible to show sperm storage in the oviducal gland. Fully developed sperm in immature organisms were identified in the testes. The main indicator of the maturity stage of males and their mating activity is the clasper. The present study provides evidence for a reliable estimation of the sexual maturity of these organisms, demonstrating the need for the combination of macroscopic and microscopic methods.