Reproduction of the spiny puffer, Diodon holocanthus (Pisces: Diodontidae) in the continental shelf of Mexican Central Pacific

Diodon holocanthus is an important economic and ecological species of the demersal fish community, caught as bycatch from local shrimp fishery. The reproductive biology of this long-spine porcupinefish has not yet been described, and reproductive season, the sex ratio, length distribution, length at first gonad maturity, and the gonad macro and microscopic features are described. A total of 400 organisms, ranging from 5.0 to 40.3 cm (average 18.4 cm) total length, were caught from the continental shelf of the Central Mexican Pacific, from December 1995 and December 1998. Sex ratio was 1:0.86 females to males (n = 253). The length at which 50% of the individuals showed maturing gonads was 19.7 cm for females and 20.1 cm for males. Length of the smallest organism with ripe gonads was 12.2 cm for females and 13 cm for males. Four gonadal maturation stages were found in both sexes, and five oocyte development phases were identified. The oocyte development pattern is of asynchronous type, which means the species can reproduce several times a year. Testicle development is lobular type, as in most teleost fishes. Monthly mean values of the gonad-somatic index suggest the reproduction activity peaks in June, and September-December.     

Reproductive cycle and reproductive output of the sea urchin Loxechinus albus (Echinodermata: Echinoidea) from Beagle Channel, Tierra del Fuego, Argentina

Reproductive cycle, frequency and duration of spawning, energetic content of gonads, and reproductive output of the common green sea urchin Loxechinus albus were analyzed in the Beagle Channel (Tierra del Fuego) between May 2004 and May 2005. Gonad indices (GI, percentages of gonad mass in total body mass) were significantly higher in March, April, July, and August than in November and May, thus showing a negative correlation with the photoperiod. Highest GI values of mature individuals were observed in August, and spawning occurred from September to December. In females, the mass-specific energy content of gonads (ECG) was highest in spawned gonads and lowest in mature ones, while in males ECG values were higher in immature stage and lower in premature and mature stages. High ECG values can be explained by the abundance of nutritive phagocytes. Both ECG and total gonad energy content (TECG) were higher in females than in males. Mean reproductive output was 7.28% for females and 6.15% for males (expressed as the difference between mean GI of mature and spawned gonads) and 25.02 kJ for females and 19.26 kJ for males (expressed as the difference between mean TECG of mature and spawned gonads).     

Gonadal histology and plasma sex steroid concentrations in maturing and mature spring migrants of Caspian lamprey Caspiomyzon wagneri in the Shirud River,southern Caspian Sea,Iran

Maturing degree-days, gonadal histology, and changes in serum sex steroids (progesterone, P; testosterone, T; and 17β-estradiol, E2) were examined in maturing and mature spring migrant Caspian lamprey Caspiomyzon wagneri (Kessler, 1870) in the Shirud River (southern Caspian Sea). Blood and gonad samples were collected from ten fish when they first entered the river (maturing stage) and from ten fish that showed spawning readiness after being held in cages in the river (mature stage). The maturing degree-days of Caspian lamprey from the start of upstream migration to maturation was 208–470°C.day. Serum P and E2 concentrations in maturing females were significantly higher than in maturing males, but in the mature stage, serum P and E2 concentrations of females were lower than males. In both stages, there were no differences in serum concentration of T between females and males. In both males and females, P increased significantly with maturation; T levels likewise appeared to increase, but the difference was not significant. E2 increased significantly with maturation in males, but females showed a significant decrease. Maturing females had similar stage gonads with the germinal vesicle in the polar position. Maturing males had testes that primarily contained secondary spermatocytes with an occasional occurrence of spermatozoa. These results suggest that males mature earlier than females, which is a pattern similar to that found in the sea lamprey.     

Reproductive biology and implications for management of the orange-spotted grouper Epinephelus coioides in the southern Arabian Gulf

The reproductive biology of Epinephelus coioides was determined from the examination of 1455 individuals collected between July 2005 and June 2007 in the southern Arabian Gulf. Histological preparations of gonads indicated that males were either derived from a juvenile phase or the transition of postspawning females, confirming a diandric protogynous sexual pattern. The spawning season was well defined, occurring once a year during April and early May. Peaks in spawning occurred after the full and new moons and was completed within a single lunar cycle. The presence of mature males over the entire size and age range and the absence of inactive mature females during the spawning season suggested that the population was not constrained by sperm limitation. While specimens undergoing sexual transition were only observed in size and age ranges of 335–685 mm total length ( L _T) and 5–6 years, patterns in the proportion of males in size and age classes suggested that sex change occurred at a relatively constant rate after female maturation up to the maximum size (1002 mm L _T) and age (11 years). Relationships between reproductive output and capacity with size and age indicated that conventional regulations that equate the mean size at first capture to sexual maturation are unsuitable for the management of E. coioides . The maximum age, small size and young age at sexual maturation ( L _min= 320 mm L _T, 2 years, for females and 242 mm L _T, 1 year, for males) conflict with the general pattern for large epinepheline groupers and may be a direct result of the intensive demersal fishery in the southern Arabian Gulf.     

Changes of major carotenoids in gonads of sea urchins (Strongylocentrotus intermedius and S. nudus) at maturation

Changes in the carotenoid content in gonads of two sea urchins species were investigated during maturation. The content of echinenones and carotenes, the two major carotenoid fractions in gonads, is highest for Strongylocentrotus intermedius at the spawning gametogenic stage of gonad maturation for both sexes. For S. nudus, the content of these pigments is highest at stages of active gametogenesis and spawning for males and at the growth stage for females. A comparison of the carotenoid content dynamics during maturation of gonads for males, females and animals at the resting (sexual inactivity) stage was also carried out.     

Reproduction of the lambari Astyanax scabripinnis (Jenyns, 1842) (Pisces: Characidae) in a small stream in Southeastern Brazil

The reproduction of Astyanax scabripinnis captured bimonthly in the Cristais small stream (20^o00'03'S and 43^o56'46'W), in the Das Velhas River basin, was studied using gross anatomical and histological techniques. Standard length of females (56 ± 8 mm) was longer than males (49 ± 6 mm). The diameter of the nucleus of the primary spermatogonia was 7.5 ± 0.9  μ m and of the spermatozoon head 1.8 ± 0.4  μ m. For the females, the oogonia nuclei measured 10.2 ± 2.2  μ m and the vitellogenic oocyte nuclei measured 675.0 ± 66.7  μ m. The following stages of the reproductive cycle were established: developing, mature, partially spent/spawned and completely spent/spawned. Maximum number of males (61.3%) and females (58.2%) at the mature stage was observed during November/December. The gonadosomatic index of males and females was highest during the mature stage (2.4 ± 0.6; 7.5 ± 1.3, respectively) and decreased in subsequent stages. In females, the hepatosomatic index was highest during the developing stage (2.8 ± 0.3), and slightly decreased in the following stages. The highest stomach repletion index found for males was observed during the partially spent stage (2.0 ± 1.2), while for the females, this index varied discretely between the reproductive stages. The highest values of Fulton's condition factor were registered during the mature stage in both sexes (2.9 ± 0.4 for males; 3.0 ± 0.3 for females). The continuous reproductive period and the presence of partially spawned females during the entire sampling period indicated that the species has fractional spawning.     

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.     

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.     

Annual reproductive cycle,spawning periodicity and sexual maturity of false scad Caranx rhonchus (Geoffroy Saint‐Hilaire, 1817) (Pisces,Carangidae) from the South‐Eastern Mediterranean (Gulf of Gabès,Tunisia)

The reproductive biology of Caranx rhonchus (Geoffroy Saint‐Hilaire, 1817) (Pisces, Carangidae) was studied in the Gulf of Gabès (Mediterranean Sea) from June 2004 to May 2006. Of 1313 individuals examined, 668 were females (50.9%) and 645 were males (49.1%). The overall sex ratio did not deviate significantly in favour of females (♀ : ♂ = 1.04 : 1). Monthly changes in the Gonado–Somatic Index (GSI) showed a rapid increase from May to June and an extended very high level from June to September (4.43–3.47% for females and 3.35–2.61% for males), before declining sharply in October (down to 2.02% for females and 0.57% for males). The gametogenesis activity began with a pre‐maturation phase from March to May, followed by a ripe‐spawning phase from June to September. From the last days of July to the end of October, the gonads were in the spent and post‐spawning stages. From November to early May, gonads were in the resting stages. The size at which 50% of the population reached sexual maturity was not significantly different between males and females :  males attained sexual maturity at fork length FL₅₀ = 161.20 ± 0.37 mm (n = 262), whereas females attained maturity at FL₅₀ = 160.70 ± 0.23 mm (n = 296). The age of maturity for both sexes occurred at 2.1 years.     

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 Astyanax fasciatus (Pisces: Characiformes) in a reservoir in southeastern Brazil

To study the reproductive biology of Astyanax fasciatus (Cuvier, 1819) in Furnas Reservoir, Minas Gerais, Brazil, a total of 1307 specimens were captured in bimonthly sampling from August 1993 to July 1994. The sex ratio showed a predominance of females, representing 65.2% of the total sample. The stages of gonadal maturation and spawning type were determined through macro- and microscopic analysis of the gonads as well as by variation in the gonadosomatic indices. A . fasciatus showed fractionated spawning and reproduction throughout the year, with spawning peaks influenced by water temperature and rainfall. Males and females initiated gonadal maturation at a mean standard length of 6.4 and 6.5 cm, respectively. During gonadal maturation, females showed a reduction in hepatosomatic index (from 1.06 to 0.83), suggesting that hepatic substances are transferred from the liver to the ovaries. In the reproductive period, A. fasciatus had lower stomach repletion and coelomic fat indices, indicating that this species ate less and consumed more fat reserves when reproduction had the maximum GSI (11.3 for females and 2.7 for males). Weight of the ovaries had a positive influence on the condition factor (K1), as the lowest K2 value (weight without gonads) were obtained during maturation, confirming the influence of the ovaries upon the physiological condition of the females. In weight–length relationship, parameter b was 3.02 for females and 2.23 for males, and the correlation coefficient ( r ²) was 0.84 and 0.66, respectively.     

The reproductive biology of Plagioscion squamosissimus (Heckel, 1840) in the Pará River estuary (Amazon Estuary)

This study describes the reproductive biology of the South American silver croaker Plagioscion squamosissimus (Heckel, 1840) in the Pará River estuary. Data were collected bimonthly from June 2007 to May 2008. In all, 334 specimens were examined. The gonads were processed with histological techniques, and the ovaries were subjected to morphometric analysis. The length at first maturity (L₅₀) values were 16.14 and 21.43 cm total length for females and males, respectively. The sex ratio based on the total number of individuals favoured the females (1.11 females: one male). Macroscopically, the gonads were classified as immature (A), maturing (B), mature (C) and spent (D). Microscopically, four germ cell types were distinguished based on the development of the ovaries. Chromatin nucleolus (I), perinucleolar (II), cortical alveoli (III) and full‐vitellogenic (IV) oocytes were observed in all ovarian stages, except that of the mature individuals which showed the largest number of full‐vitellogenic oocytes (IV), with a mean diameter of 565.4 μm (±147.4). Substantial percentages of individual P. squamosissimus were found to be in a reproductive condition. Reproductive activity was recorded throughout the year in the Pará River estuary, primarily in February/March and August/September.     

Reproductive cycle of seabob shrimp Xiphopenaeus kroyeri (Crustacea,Penaeidea) from the northeast coast of Brazil

The reproductive cycle of Xiphopenaeus kroyeri north-eastern Brazil was described to contribute to the sustainable management of this stock in the region. Specimens were collected monthly from August 2011 to July 2012 using a local vessel of the artisanal fleet. A total of 1201 individuals were analyzed (673 females and 528 males) with a mean carapace length (CL) of 1.88 ± 0.16 cm and total length (TL) of 9.00 ± 1.22 cm. The lowest CL and TL of mature females were 1.33 and 6.5 cm, respectively, and all females above 2.44 cm (CL) and 11.5 cm (TL) were mature. Ovarian maturation was classified into four stages: I (immature), II (maturing), III (mature) and IV (spawned). Individuals of all maturational stages were present throughout the year. Considering the macro and microscopic analysis, it was suggested that this species in north-eastern Brazil has a continuous reproductive cycle, with two seasonal peaks, November/December and February (austral spring and summer). A positive correlation between the percentage of mature females and temperature was observed, and a higher percentage was reported in the warmer months of the year. This suggests that the reproductive peaks can be triggered by water temperature variation throughout the year.     

Reproductive and population parameters of spiny dogfish Squalus acanthias in the south‐western Atlantic Ocean

The objective of this study was to estimate reproductive and population parameters of the spiny dogfish Squalus acanthias for the south‐western Atlantic Ocean. In total, 2714 specimens (1616 males and 1098 females) were collected from surveys carried out using research vessels. Males ranged from 225 to 861 mm total length (L_T) and females from 235 to 925 mm L_T. The size at maturity of females (651 mm) was significantly greater than that of males (565 mm). The maximum proportion of mature individuals (P_max) of the gestation ogive was <1, which indicates that a proportion of mature females was not in gestation. This inactivity may be explained by the occurrence of resting periods between cycles or by the asynchrony of the reproductive cycle. The estimated P_max for the maternity ogive suggested that about one third of mature females were in the maternity stage (i.e. with embryos >156 mm). The temporal and spatial co‐occurrence of non‐gravid adult females at different stages of ovarian development, as well as gravid females at all embryonic development stages would indicate that the female reproductive cycle in the south‐western Atlantic Ocean is asynchronous. The results indicate that S. acanthias is susceptible to fishing pressure on account of its length at maturity, extended reproductive cycles and low fecundity.     

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.     

Reproductive biology of a Gobiid fish Oxyurichthys tentacularis (Valenciennes, 1837) inhabiting Ashtamudi Lake,S. India

Reproductive traits of Oxyurichthys tentacularis, a most demanded fish in Ashtamudi Lake, S. India were studied from samples collected using gill net, cast net and dip net during 2013–2015. Sexes were separated by observing the urogenital papilla in males and the gonads. Five maturity stages were identified by examining the gonads. Though advanced maturity stages were encountered throughout the year, higher preponderance of ripe gonads was discernible during August to November and February to April. Gonadosomatic indices indicated same trend in both sexes. The length at first maturity was 86.67 mm in males and 80.17 mm in females. The absolute fecundity ranged from 5,112 (102 mm TL) to 52,431(175 mm TL). Fecundity established linear relationships with total length, body weight and ovary weight. Ova diameter studies revealed that spawning takes place in batches at regular intervals and the species is a multiple spawner. The ratio of males to females was found to be 1:0.7 (χ² = 10.8; p < 0.05). The pooled average for the whole period showed a perceptible dominance of male population in all of the months except in January (χ² = 2.3; p > 0.05) could be observed.     

Ecology of Allis Shad Alosa alosa and Twaite Shad Alosa fallax in the Solway Firth, Scotland

The basis of this study were 132 adult Allis Shad and 150 Twaite Shad collected as bycatches from salmon stake nets in Scotland on the north side of the Solway Firth. Most (60%) of the Allis Shad were immature fish 2–3 years of age (mean length 305 mm). Mature males were younger (3–5 years) and smaller (mean length 421 mm) than females (4–6 years and 481 mm mean length). The largest Allis Shad was a female of 515 mm and 2183 g. In contrast, almost all the Twaite Shad were mature, the males younger (3–5 years) and smaller (mean length 341 mm) than the females (4–6 years and 364 mm mean length). The largest Twaite Shad was a female of 400 mm and 1213 g. The food of Allis Shad consisted mainly of small zooplankton with some fish and larger Crustacea. Fine vegetable fragments were common in the stomachs and attributed to filter feeding. The food of Twaite Shad was mainly small fish with some Crustacea. Mature Allis Shad of both sexes with large gonads (maximum female GSI: 20.63) were found throughout the spring and summer but no definite evidence of local spawning was obtained. Mature Twaite Shad of both sexes with large gonads (maximum female GSI: 23.32) were found until early July, thereafter most of the fish were spent. It appears that Twaite Shad spawn locally in June. Some hybrids between the two species were found.     

New data on the reproductive biology of shortspine thornyhead <Emphasis Type="Italic">Sebastolobus alascanus</Emphasis> (Sebastidae) in the northwestern Pacific

New data on fecundity, sex ratio in different size groups, and the rate of sexual maturation of shortspine thornyhead Sebastolobus alascanus in the northwestern part of the Pacific Ocean are provided. Individual absolute fecundity of the studied females varies in the range of 175 000–821000 (on average, 392500) eggs. In Pacific waters off the Kuril Islands and Kamchatka, among individuals with a length to 41 cm, males dominate; in size groups of 42–59 cm, sex ratio is almost equal; among larger fish, females prevail. In the western part of the Bering Sea among analyzed fish with a length to 44 cm, sex ratio is almost equal; among larger individuals, females dominate. Half of males and females of shortspine thornyhead off the eastern coast of the northern Kuril Islands and southeastern Kamchatka mature at a length of approximately 41 cm that can be recommended as a commercial size for the given species in this area.     

Sexual size dimorphism,growth, and maturity of the fluvial eight-barbel loach in the Kako River,Japan

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.