Life history of the nonnative convict cichlid <Emphasis Type="Italic">Amatitlania nigrofasciata</Emphasis> in the Haebaru Reservoir on Okinawa-jima Island,Japan

Life history parameters associated with reproductive biology, age, and growth of the convict cichlid (also known as the zebra cichlid) Amatitlania nigrofasciata, which was introduced into the Haebaru Reservoir on Okinawa-jima Island, were estimated using 437 specimens that ranged from 13.7 to 82.9 mm standard length (SL). Lengths of females at first maturity (SL) and 50% maturity (L ₅₀) were estimated to be 32.2 and 37.3 mm SL, respectively. The spawning period continued throughout the year, with a peak spawning cycle from March to May 2006–2007. Observations of postovulatory follicles and tertiary yolk stage oocytes indicate that convict cichlids spawn multiple times within a year. Female cichlids that hatched during the peak spawning seasons matured after October of the same year. Batch fecundity of females (32.2–61.2 mm SL) ranged from 65 to 345 (mean ± SD = 155 ± 63). Opaque zones along the outer margins of otoliths formed annually. The maximum age of male and female cichlids was 3 years. The von Bertalanffy growth formulae (VBGF) were expressed as L_t = 57.4( 1 - e ^{- 0.78( t + 0.91 )} ) {{\hbox{L}}_{\rm{t}}}{ = 57}{.4}\left( {1 - {e^{ - 0.78\left( {t + 0.91} \right)}}} \right) for females and L_t = 69.5( 1 - e ^{- 1.07( t + 0.24 )} ) {{\hbox{L}}_{\rm{t}}}{ = 69}{.5}\left( {1 - {e^{ - 1.07\left( {t + 0.24} \right)}}} \right) for males. Males grew larger than females beginning from the first year. Certain life history characteristics, such as year-round spawning and early maturation, probably contributed to the successful establishment of the convict cichlid, and this species in particular is thought to adapt and become established quickly upon introduction to freshwater systems on Okinawa-jima Island.     

Reproductive biology of the migratory freshwater fish Salminus brasiliensis (Cuvier, 1816) in the Cuiabá River basin,Brazil

This study provides information on the reproductive biology of the dorado Salminus brasiliensis from the Cuiabá River basin, through determinating life history trajectories (length at first maturity, fecundity and spawning type) and the reproductive period, thus establishing the relationships between biotic factors and rainfall and river levels that might act as potential triggers for maturation and spawning. Salminus brasiliensis is a migratory species of great commercial and ecological importance. Individuals were collected monthly from August 2013 to July 2014 in the Cuiabá River. Analyses were performed based on biometric data and the gonads. Females attained greater lengths than males in the Cuiabá River basin, and with a significant difference in the sex ratio in favor of females. Peak reproductive activity occurred in November and December and was related to rainfall. Reproduction was seasonal, with spawning and reproductive potential correlating positively with the length and mass of the gonads of mature females. Average length at first maturity for females was estimated at 55 cm. A regular (annual) monitoring programme of essential biological variables to support a trend analysis over years (not just a snapshot study, as this one) is strongly recommended in order to give advice for the proper fishing policies in the region, as without regular basic data on the population dynamics, management is not possible.     

Aspects of reproductive biology of the red goby Trypauchen vagina (Gobiidae) from the Mekong Delta

This study provides knowledge on reproductive traits of Trypauchen vagina, a target fish for catching, based on data analysis of 701 individuals collected in the Mekong Delta from January to December 2015. The species is a multiple spawner depositing eggs in early wet season (June–August) since gonadosomatic index reaches a high point during this period, supported by the appearance of ripe and spent gonads at that time. Male and female fish matures firstly at 16.59 and 16.81 cm in total length respectively. The species displays high batch fecundity (4,000–12,750 eggs/female). Knowledge of length at first maturity and spawning season is essential for local authorities to set the suitable fish length and time for fishing. The results provide fundamental information on the reproductive biology and contributed to knowledge for fish population sustainable management.     

Maturity and fecundity of golden grey mullet (Liza aurata Risso, 1810) in Iranian waters of the Caspian Sea

The objective of the study was to determine some reproductive parameters in the golden grey mullet (Liza aurata Risso, 1810) during two periods half a decade apart while also trying from limited data to identify changes in fecundity over the past half century. Maturity and fecundity of golden grey mullet caught in Iranian waters of the Caspian Sea is not well documented and were thus studied during several seasonal cycles during 2002–2004 to establish basic data on reproduction in the area. The fork length (FL) of 462 sampled fish was between 22.1 and 51.9 cm. The fork length–weight relationship derived from all fish was W = 0.0118FL^2.964. Overall male to female ratio was 1 : 1.42. The reproductive season extended from October to December. Fifty percent of sexual maturity was at FL 26.0 cm. Mature gonads were present in 20% of fish at age 3, 63% at age 4, 88% at age 5, and 97% at age 6. Individual absolute fecundity of the golden grey mullet ranged from 113 386 to 1.47 million eggs, with a mean (±SD) of 451 963 (±274,114.2). An overlap exists between the spawning and fishing seasons. Therefore, the start of the fishing season should be delayed for 1 month in order for stocks to complete their spawning.     

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.     

Reproductive biology of Pethia ticto (Cyprinidae) from the Gorai River (SW Bangladesh)

Some aspects of reproductive biology of Pethia ticto (Hamilton, 1822) from the Gorai River of southwestern (SW) Bangladesh were investigated by regular monthly samples for a period of one year during July 2010 to June 2011. A sum of 1200 specimens (male = 454 and female = 746) were collected using cast net, lift net and conical trap. Total length (TL) and Body weight (BW) were measured with slide caliper and digital balance, respectively for each individual. Based on gonadosomatic index (GSI), modified gonadosomatic index (MGSI) and Dobriyal index (DI) first sexual maturity was 4.30 cm TL for male and 4.80 cm TL for female. Also, on the basis of higher values of GSI, MGSI and DI spawning season was ranged from April to September for P. ticto in the Gorai River ecosystem. The fecundity was ranged from 2230–8450 with a mean value of 4779 ± 1578. In addition, there was a significant relationship between total length and fecundity (r² = .931, p < .001); body weight and fecundity (r² = .943, p < .001). Therefore, the findings of this study would be very effective for sustainable management of this threatened species in the Gorai River and surrounding ecosystem.     

Gonad maturation and spawning of cobia,Rachycentron canadum (Linnaeus, 1766) off the Dungun coast,Malaysia

The reproductive biology of cobia, Rachycentron canadum, from the coastal waters of Dungun, Malaysia was studied from June 2014 to May 2015. From commercial trawls, a total of 201 samples (combined sexes) were collected (fork lengths [FL] 37.5–124.0 cm; body weights 0.5–20.4 g). The overall sex ratio of females to males was 1:0.9, which was not significantly different (χ² = 2.12, df = 1; p < .05). Estimations of length at 50% maturity (L₅₀) showed that both sexes matured at approximately 75 cm FL; estimated spawning frequency was 6 days. Mean batch fecundity (BF) ranged from 0.55 to 4.32 million eggs. The average number of eggs per gram of ovary was from 2,100 to 5,400 eggs, and relative fecundity 147 eggs/g. There was a weak positive correlation (r² = .48) between BF and female FL as well as BF with an ovary‐free body weight (r² = .56), possibly due to females being in a continuous spawning condition and some possibly half‐spent, based on the histological examination of the female gonads. Despite cobia being asynchronous spawners, the gonadosomatic index in both males and females showed peaks in June, November, and particularly March. Based on histological examination, spawning‐capable males were encountered throughout the study period, whereas spawning‐capable females in the late developing subphase were found mostly in March and April. This is the first study on the reproductive aspects of cobia in Malaysian waters.     

Reproductive traits of shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque, 1820) in the lower Platte River,Nebraska

We assessed reproductive status, fecundity, egg size, and spawning dynamics of shovelnose sturgeon Scaphirhynchus platorynchus in the lower Platte River. Shovelnose sturgeon were captured throughout each year during 2011 and 2012 using a multi‐gear approach designed to collect a variety of fish of varying sizes and ages. Fish were collected monthly for a laboratory assessment of reproductive condition. Female shovelnose sturgeon reached fork length at 50% maturity (FL₅₀) at 547 mm and at a minimum length of 449 mm. The average female spawning cycle was 3–5 years. Mean egg count for adult females was 16 098 ± 1103 (SE), and mean egg size was 2.401 ± 0.051 (SE) mm. Total fecundity was positively correlated with length (r² = 0.728; P < 0.001), mass (r² = 0.896; P < 0.001), and age (r² = 0.396; P = 0.029). However, fish size and age did not correlate to egg size (P > 0.05). Male shovelnose sturgeon reached FL₅₀ at 579 mm and at a minimum length of 453 mm. The average male spawning cycle was 1–2 years. Reproductively viable male and female sturgeon occurred during the spring (March–May) and autumn (September–October) in both years, indicating spring and potential autumn spawning events. Shovelnose sturgeon in the lower Platte River are maturing at a shorter length and younger age compared to populations elsewhere. Although it is unknown if the change is plastic or evolutionary, unfavorable environmental conditions or over‐harvest may lead to hastened declines compared to other systems.     

Age,growth and reproductive traits of invasive goby Taenioides cirratus in the Chaohu Lake,China

The eel goby Taenioides cirratus (Blyth, 1,860) is a small fish inhabits muddy bottoms of brackish-water in the Indo-West Pacific. It has invaded many inland freshwater lakes in China, such as the Chaohu Lake, Gaoyou Lake and Nansi Lake, and its population increased rapidly in these freshwater lakes in recent years. The age, growth and reproductive traits of T. cirratus invading the Chaohu Lake were studied. A total of 482 specimens (210 females, 204 males and 68 juveniles) with total length (TL) ranging from 9.4 to 20.6 cm were collected using the benthic fyke nets at monthly intervals from March 2018 to February 2019. The sagittal otolith was used for age determination. Monthly variation of marginal increment ratio indicated that the annual forming of opaque band on sagittal otolith was completed during March and April. For both sexes, only four (from 0+ to 3+ years) age groups were observed and 1+ and 2+ years age individuals dominated the population. Back calculated length at age showed males grew faster than females. Both sexes reached maturity at 1+ year age and the TL at first maturity (TL₅₀) was 12.6 cm for females and 11.9 cm for males. Monthly variation of gonado-somatic index indicated that the spawning occurred from May to August. The fecundity ranged from 967 ova to 5,114 ova, with a mean of 3,205 ova. Our study provides a comprehensive data on the key life history traits of T. cirratus for the first time.     

Life‐history traits and population decline of the Atlantic mackerel Scomber scombrusin the Adriatic Sea

This study investigated demographic structure and reproductive characteristics of the Atlantic mackerel Scomber scombrus, in relation to landing trends in the northern‐central Adriatic Sea. Results highlighted the occurrence of only small‐sized and young‐age individuals, and a marked decline from the 1990s to the present in maximum age (from 8 to 3 years) and total length (L_T; from 420 to 360 mm). Fecundity ranged between 40 000 and 190 000 eggs, and was related to female L_T. High levels of atresia implied lower values of actual fecundity. Sexual maturity was attained by 72·8% of individuals in their first year of life at 200 mm. The reduction in maximum L_T resulted in a marked decline in the population egg production, while the reduction in maximum age implied that females participated in fewer spawning events.     

Reproductive traits of the “ocellated killifish” Floridichthys polyommus Hubbs, 1936 (Pisces: Cyprinodontidae) inhabiting estuary of the Champotón River (Campeche,Mexico)

This study explores the reproductive biology and the influence of environmental factors on the reproductive traits of Floridichthys polyommus inhabiting the estuary of the Champoton River. The analysis included population structure, gonadal developmental stages, reproductive period, size at first sexual maturity, fecundity, sex ratio, and somatic indexes. A spatio‐temporal pattern in the distribution of the seven size classes was detected. The species showed a positive allometric growth. Sex ratio was 1.21:1 (females:males). Size at first maturity was 42.23 mm (females) and 47.8 mm (males). A higher absolute and relative fecundity was detected in Puente Champotón estuary (PCH) with lower salinities than those detected in the Delta (DE). The adaptive significance of this trait could be in response to the heavy osmotic constraint imposed by extreme salinities in the DE. Floridichthys polyommus prefers PCH for spawning, and as a result a higher number of ripe individuals was observed in this site, characterized by the highest nutrient levels, which can boost productivity and food availability for fish. Hepatosomatic index was negatively correlated with gonadosomatic index, suggesting energy transfer from the liver towards gamete production. Floridichthys polyommus exhibits an opportunistic strategy (early maturity, small oocytes, small clutches) suggesting that energy is allocated towards reproduction to compensate for the unpredictable hydrological conditions imposed by the estuary (particularly during the hurricane season). Floridichthys polyommus shows a reproductive strategy exhibited by fish living in unstable systems. A seasonal divergence was observed in the reproductive traits of F. polyommus, while differences between study sites were for fecundity.     

Spawning season and size at sexual maturity of <Emphasis Type="Italic">Kyphosus bigibbus</Emphasis> (Kyphosidae) from northwest Kyushu,Japan

The reproductive characteristics of Kyphosus bigibbus were examined using individuals collected between June 2004 and February 2009 off Nagasaki Peninsula in northwest Kyushu, Japan. The spawning season and size at sexual maturity of this species were characterized based on a gonad index and histological examination of the gonads. The spawning season extends from June to October. This species is assumed to be an indeterminate, multiple-batch spawner. Females reached sexual maturity at larger size than males (fork length at 50% sexual maturity: males 284 mm, females 360 mm).     

Reproductive biology and spawning strategy of the catadromous percichthyid, <Emphasis Type="Italic">Macquaria colonorum</Emphasis> (Günther, 1863)

The reproductive biology and spawning strategy of the iconic catadromous percichthyid, estuary perch Macquaria colonorum was examined from three coastal rivers of south-eastern (SE) Australia. Ovarian and testicular development followed a pattern similar to that of other percichthyids, world-wide. Females were collected in significantly larger sizes and greater numbers from all, and two of the three rivers, respectively. Mean size and age at maturity was greater for females (25.05 cm FL ± 0.85 and 3.75 yrs ± 0.08, respectively) than males (22.21 cm FL ± 0.50 and 3.28 yrs ± 0.08 respectively), with no significant difference between rivers. Trends in gonadosomatic indices indicated that M. colonorum spawn in the austral winter-spring in SE Australia. However, peak spawning occurred earlier (June-August) in the two most northern rivers (Hawkesbury and Clyde) compared with the Bemm River (September-November) further south. Ripe females were captured only in the lower reaches of estuaries throughout the spawning period in all three rivers. Mature M. colonorum females displayed a group synchronous pattern of oocyte development suggesting a multiple spawning strategy. Mean batch fecundity (F _B ) was 266 583 ± 17 821 oocytes per female and relative fecundity was 377 ± 10 oocytes.g^-1 body weight. There were significant power relationships between F _B and fork length (FL), weight and age. Similar to other percichthyids, M. colonorum are long-lived, highly fecund and exhibit a flexible spawning strategy which is attuned to the highly variable environments in which they are found.     

Consistency in the life history traits of four invasive pseudorasbora parva populations in Southern England

Life history plasticity can be a strong predictor of the establishment and invasion success of introduced fishes. Here, the life-history traits of four P. parva populations in adjacent ponds in Southern England were measured throughout 2013 to determine the timing and length of their reproductive season and the extent of trait plasticity. The relative abundance of the populations (as catch per unit effort) was similar, with low variability in their traits relating to reproductive effort and somatic growth. All the populations were male dominated. Both sexes matured at small body sizes, with fish as small as 30 mm being mature in both sexes, with the age at maturity for both sexes being age 1+ years. The peak spawning period, characterised by female fish investing heavily in reproduction when their gonado-somatic index (GSI) values were highest and declined thereafter, occurred in May and June, and after a mean of 212 ± 24 degree-days >12°C, and with water temperatures being 13.2–14.6°C. There were no further peaks in GSI, despite the species being considered to have prolonged spawning periods across spring and summer. These results also suggest that whilst the expression of life-history traits of invasive fishes often vary with density, they can be highly consistent between populations at similar abundances and locations.     

Maturity Ogives for South Pacific Albacore Tuna (Thunnus alalunga) That Account for Spatial and Seasonal Variation in the Distributions of Mature and Immature Fish

Length and age at maturity are important life history parameters for estimating spawning stock biomass and reproductive potential of fish stocks. Bias in estimates of size and age at maturity can arise when disparate distributions of mature and immature fish within a population are not accounted for in the analysis. Here we investigate the spatial and temporal variability in observed size and age at maturity of female albacore tuna, Thunnus alalunga, using samples collected across the South Pacific. Maturity status was identified using consistent histological criteria that were precise enough to allow for mature but regenerating females to be distinguished from immature females during the non-spawning season, permitting year-round sampling for maturity estimation in albacore. Using generalised linear mixed models, we found that the proportion of mature females at length varied significantly with latitude and time of year. Specifically, females at northern latitudes (∼10–20°S, where spawning occurs) were mature at significantly smaller lengths and ages than females at southern latitudes (∼20–40°S), particularly during the spawning season (October–March). This variation was due to different geographic distributions of mature and immature fish during the year. We present a method for estimating an unbiased maturity ogive that takes into account the latitudinal variation in proportion mature at length during a given season (spawning or non-spawning). Applying this method to albacore samples from the western region of the South Pacific gave a predicted length at 50% mature of ∼87 cm fork length (4.5 years).     

Age, growth and reproductive parameters of the Mediterranean cardinal fish, Apogon imberbis

Life history parameters (age, growth and reproductive characteristics) of the Mediterranean paternal mouthbrooding cardinal fish, Apogon imberbis, were investigated at a coastal locality off Blanes, NW Mediterranean Sea. Maximum age was found to be 5 years for both sexes. Age was validated with an otolith chemical (tetracycline) marking experiment. Both females and males reached maturity at length >5.5 cm, corresponding to 1 year of age in both sexes. The spawning season ranges from July to October, with a peak in August. The number of eggs in the mouths of males increased linearly with fish total length.     

Reproductive strategy of Leporinus piau (Fowler, 1941), a neotropical freshwater fish from the semi‐arid region of Brazil

This study concerns the reproductive strategy of the freshwater fish, Leporinus piau, native to the Brazilian semi‐arid region. The hypothesis of this work predicts that the species would spawn during the rainy season, presenting a seasonal reproductive strategy. The study investigated the structure of total body length and body mass, sex ratio, body size at first sexual maturity, developmental stages of gonads, fecundity, gonadosomatic index (GSI), condition factor (K) and the spawning season of L. piau. Twelve monthly samplings (mean n = 18) were carried out in 2009 and environmental parameters such as rainfall, temperature, pH, electrical conductivity and concentration of dissolved oxygen of water were registered. The sampled population of L. piau (n = 211) showed a slight predominance of males (55%), but with larger and heavier females. First sexual maturation in males occurred earlier (16.5 cm total length) than in females (20.5 cm total length). The species is a total spawner with an average fecundity of 55 000 mature oocytes. Rainfall (225 ± 7.2 mm) and concentration of dissolved oxygen (8.5 ± 0.2 mg L^?1) acted as influential factors during the spawning season. The monthly GSI shows that spawning starts when the rainy season is at its maximum and ends synchronously (females r = 0.91; males r = 0.89) with the end of the rainy season. L. piau presents a seasonal reproductive strategy with high reproductive output, providing a population increase and exploitation of the environmental resources.     

Length‐weight relationship and reproductive parameters of Botia dario (Hamilton, 1822) in Assam,India

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 (L_m50) 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).     

Reproductive strategy of Psectrogaster rhomboides Eigenmann & Eigenmann, 1889, a freshwater fish from Northeastern Brazil

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.     

Fecundity regulation by atresia in turbot Scophthalmus maximus in the Baltic Sea

Down‐regulation of fecundity through oocyte resorption was assessed in Baltic Sea turbot Scophthalmus maximus at three locations in the period from late vitellogenesis in April to spawning during June to July. The mean ± s.d . total length of the sampled fish was 32·7 ± 3·1 cm and mean ± s.d . age was 6·2 ± 1·5 years. Measurements of atresia were performed using the ‘profile method’ with the intensity of atresia adjusted according to the ‘dissector method’ (10·6% adjustment; coefficient of determination was 0·675 between methods). Both prevalence (portion of fish with atresia) and intensity (calculated as the average proportion of atretic cells in fish displaying atresia) of atresia were low in prespawning fish, but high from onset of spawning throughout the spawning period. Atretic oocytes categorized as in early alpha and in late alpha state occurred irrespective of maturity stage from late prespawning individuals up to late spawning fish, showing that oocytes may become atretic throughout the spawning period. Observed prevalence of atresia throughout the spawning period was almost 40% with an intensity of c. 20%. This indicates extensive down‐regulation, i.e. considerably lower realized (number of eggs spawned) v. potential fecundity (number of developing oocytes), suggesting significant variability in reproductive potential. The extent of fecundity regulation in relation to fish condition (Fulton's condition factor) is discussed, suggesting an association between levels of atresia and fish condition.