Reproductive biology of the South West Atlantic marbled sand skate Psammobatis bergi Marini, 1932 (Elasmobranchii, Rajidae)

The reproductive biology of Psammobatis bergi was investigated based on 92 males and 136 females skates taken from the coastal bottom trawl fishery at Puerto Quequén, Argentina. The relationship between total body mass and total length (TL) was not significantly different between sexes, but females were heavier than males. Minimum length at maturity in males was 451 mm TL with a length ratio of 74%, whereas females were 415 mm TL with a length ratio of 74%. TL at which 50% of males were mature was 457.6 mm (75.6% of the largest male) and for females was 441.6 mm (79.1% of the largest female). The results indicate a continuous reproductive cycle during the year, with a maximum number of females carrying egg cases in warmer seasons.     

Age, growth and reproduction of the black scorpionfish, Scorpaena porcus (Pisces, Scorpaenidae), on the Black Sea coast of Turkey

Age, growth and reproduction of the black scorpionfish, Scorpaena porcus were studied in specimens from the coast of the Sinop Peninsula (Black Sea) between March 2002 and April 2003 in order to characterize these population parameters in comparison to specimens from populations of nearby regions. A total of 1086 specimens was captured by beam trawl at the depths between 0 and 30 m. The total number of females (510) was significantly higher than that of males (373). Total length of males and females ranged between 5.7 and 23.6 cm, and 4.9 and 31.7 cm, respectively. The length–weight relationship showed a positive allometric growth. Females grew faster and reached a larger size at age than males ( L _∞ = 111.9 cm, K  = 0.035 year⁻¹, φ' = 2.64 for females, and L _∞ = 74.6 cm, K  = 0.054 year⁻¹, φ' = 2.49 for males). The age range estimated was up to 8 years for females and 5 years for males. Reproduction likely occurs between June and September. Sex ratio varied greatly with season, perhaps indicating different seasonal migratory patterns in adults of different sex. An inverse correlation between gonadosomatic index (GSI) and hepatosomatic index (HSI) was evident during the reproduction seasons. The mean size at first sexual maturity was 17.5 cm TL for females, and 16.7 cm TL for males.     

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.     

Growth and life history traits of Aegean chub,Squalius fellowesii (Günther, 1868) in streams in Muğla Province,Aegean coast,Turkey

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.     

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.     

Reproductive biology of Rioraja agassizi from the coastal southwestern Atlantic ecosystem between northern Uruguay (34°S) and northern Argentina (42°S)

A total of 552 individuals of Rioraja agassizi (257 females and 295 males) were collected by bottom-trawl during research cruises. Sexual dimorphism was observed with females are heavier than males for a given total length (TL). Using logistic regression, it was determined that TL at 50% maturity of males was 475 mm TL and of females 520 mm TL. This estimation agrees with the morphological parameters measured. Although not statistically significant, a peak in reproductive activity was observed in males during late spring and summer. The monthly variation in the gonadosomatic index and oviducal gland width, together with the largest diameter of ovarian follicles, suggests that R. agassizi females have a partially defined annual reproductive cycle with two peaks, one from November (spring) to February (summer) and another in July (winter).     

Reproductive biology of the Brazilian guitarfish,Pseudobatos horkelii (Müller & Henle, 1841) from southeastern Brazil,western South Atlantic

This study provides information on the seasonal occurrence, length‐width relationship, sexual development and size at first maturity of the critically endangered Brazilian guitarfish Pseudobatos horkelii in southeastern Brazil. Samples were obtained from September 2007 to August 2009 from commercial fisheries off São Paulo State coast at depths of 10–50 m, with net mesh sizes of 150 mm in the main net and 100 mm in the cod end. A total of 143 specimens (71 males, 72 females) were analyzed. Total length (TL), disc width (DW), sex and reproductive variables were recorded for each individual. Pseudobatos horkelii presents sexual dimorphism in length‐width relationships, with females attaining larger TL and DW. Females also mature at a larger TL, at 81.1% of the maximum TL, while males mature at 67.8% of the maximum TL. No specimens were captured in winter, and only a small sample size was observed in autumn. Males captured in spring and summer presented semen in the seminal vesicle, indicating that this species may reproduce in the warmer months, as already observed for other Rhinobatidae as well as for P. horkelii in southern Brazil.     

Reproductive biology of Psammobatis extenta

Psammobatis extenta collected from the commercial bottom trawl fishery operating in Puerto Quequén, Argentina, between 2000 and 2001, had a sex ratio of 1:1 (535 specimens). Both the largest male and female measured 313 mm total length ( L _T). The relationship between total body mass and L _T was significantly different between sexes; mature females weighed more than mature males for a given L _T. The size at which 50% of males were sexually mature was 262 mm L _T (83·6% of the maximum size), whereas 50% of females were mature at 249 mm L _T (80·0% of the maximum size). The gonadosomatic index in mature males and females was slightly higher during summer, but did not show significant variation over the sampling period. The hepatosomatic index of males and females was higher during the autumn and winter and followed a distinct seasonal pattern. Evidence suggested a continuous reproductive cycle during the year, with a maximum number of females carrying egg-cases in summer.     

浙江丽水中国石龙子的食性、两性异形和雌性繁殖

丽水分布的中国石龙子（Ｅｕｍｅｃｅｓ ｃｈｉｎｅｎｓｉｓ）摄入的食物均为无脊椎动物,分别属于环节、软体和节肢动物,涉及３０余科,成体和幼体的食物生态位宽度分别为７．２６和６．６９,成体的幼体的食物生态们重叠度为０．５９。性成熟雄性个体大于雌体。成雄和幼体的头长和头宽随体长ＳＶＬ的增长速率大于成雌,成雄头长随ＳＶＬ的增长速度显著大于幼体,成雌和幼体的头长随ＳＶＬ的增长速率无显著差异。成雄头部大于成雌     

Reproductive biology of two sympatric skates in the south‐west Atlantic: Psammobatis rudis and Psammobatis normani

The total lengths ( L _T) at which 50% were mature of Psammobatis rudis and Psammobatis normani , in the south‐west Atlantic were: P. rudis , 428 mm for males and 414 mm for females and P. normani , 443 mm for males and 403 mm for females. Clasper length in mature males was greater in P. normani than in P. rudis , whereas oviducal gland width was not different between species. Females of P. normani with egg cases were found in every month sampled, and in January, March, April and July in P. rudis , although insufficient samples were available to identify peak oviposition times. Geographic variation in size frequency and maturity were found. The effects of oceanographic conditions and fishing pressure are discussed. Size at 50% maturity in both species was >74% of the maximum L _T, indicating late sexual maturity and low potential stock recovery rate.     

Growth and reproduction of Mesopotamian spiny eel (Mastacembelus mastacembelus Banks & Solander, 1794) in Ataturk Dam Lake (Şanliurfa), Turkey

Age at length, growth and reproduction of 220 Mastacembelus mastacembelus specimens from the Atatürk Dam Lake were studied from July 2005 to July 2006. Total lengths and weights ranged from 7.0 to 85.0 cm and from 6 to 1100 g, respectively. Maximum age was 13 years. The regression model fitted to length and weight data was W  =   0.0228  L ^2.43 for males and W  =   0.0029  L ^2.95 for females. The von Bertalaffy growth equations for males and females were L _t  = 99.2 [1−e^{−0.11 ( t −0.12)}] and L _t  = 69.2 [1−e^{−0.26 ( t −0.35)}], respectively. Males dominated especially at an older age; the overall sex ratio was 1 : 0.63 (M:F). The breeding period was from May to July. Fecundity ranged from 2540 to 24 000 eggs per female.     

Difference in age,growth, and sexual demography of black‐spot tuskfish,Choerodon schoenleinii (Valenciennes, 1839), in two adjacent populations,Ryukyu Archipelago,southern Japan

To better understand the plasticity of life history traits in the blackspot tuskfish, Choerodon schoenleinii (Valenciennes, 1839), the characteristics of the population around the Yaeyama Islands (24°N, 124E) were examined and compared to those around Okinawajima Island (26°N, 128E) that had been investigated in a previous study. Age and growth of the Yaeyama population were examined based on 103 specimens collected at fish markets between 2006 and 2016. Specimens included 83 females (25.2–69.0 cm total length [TL]), and 20 males (43.1–71.8 cm TL). Ages determined from sectioned otoliths ranged from 1–9 for females, and 4–15 for males. Values for von Bertalanffy growth functions were L_t = 74.2 {1?exp[?0.23 (t + 0.38)]}, and the growth of the Yaeyama population was significantly faster than that of the previously studied population. Sexual demography of the two populations was compared using body length data on landings measured at the fish markets. In the Yaeyama population, females and males ranged from 24–65 cm TL and 39–75 cm TL, respectively; length at 50% individual sex change size was estimated at 54.7 ± 0.56 cm (±95% C.I.). In contrast, in the Okinawajima population, females and males ranged from 16–65 cm TL and 30–75 cm TL, respectively; meanwhile, 50% sex change size was estimated to be 50.0 ± 0.25 cm. There were thus significant differences in the size at sex change between the two populations. This difference may be related to the difference in population density between the sites.     

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.     

Body mass variation in Marbled Murrelets in British Columbia, Canada

Body mass was measured in Marbled Murrelets Brachyramphus marmoratus from May to August, 1994–1998 at Desolation Sound, and during June and July 1997 at Mussel Inlet, British Columbia, Canada, to assess seasonal, sexual, site and intra-annual variation. Birds were captured by mist-net, and by night-lighting, and were sexed using molecular techniques. The breeding status of females (gravid or not) in 1997 was determined from plasma levels of egg-yolk precursors. Adult males weighed 203.7 ± 14.8 g, n  = 495 (juveniles 166.6 ± 28.8 g, n  = 31) and females weighed 201.2 ± 20.5 g, n  = 344 (juveniles 148.3 ± 23.5 g, n  = 20). Murrelets caught in mist-nets were significantly lighter than those caught by night-lighting. Female mass was constant across years of the study, but males caught by night-lighting were heavier in 1998 than in 1997. Females declined in mass during the egg-laying period, but when gravid females were removed from the analysis, or when the post-laying data were analysed, no declines were found. Marbled Murrelets appear to maintain mass at a constant level all season, and are probably more income than capital breeders. Variation in body mass in this species may be constrained by the need to fly with speed and agility to avoid aerial predators.     

Production,maturity, reproductive cycle and fecundity of small-spotted catshark,Scyliorhinus canicula (Chondrichthyes: Scyliorhinidae) from the northern coast of Tunisia (Central Mediterranean)

Small-spotted catshark Scyliorhinus canicula (Linnaeus, 1758) is confronted since 2000 to a drastic decline of captures in Tunisian northern areas where it formerly was quantitatively and qualitatively very abundant. A study conducted in the area showed that males and females sexually matured between 400–478 mm and 364–471 mm total length (TL), respectively. The largest male and female were 521 mm and 531 mm TL, respectively and weighed 449 and 445.5 g, respectively. There was a not significant relationship total mass vs. TL between males and females. Conversely, the relationship of liver mass vs. TL significantly differed between sexes. Both HSI and GSI values did not present significant differences between males and females. There was a not significant relationship total mass vs. TL between males and females. Both male and female HSI reached high values in adults, significantly higher than those of sub-adults. Both male and female GSI values increased with TL of specimens; additionally, they showed significant differences between juveniles and sub-adults and also between sub-adults and adults. The OSI values were significantly different between juvenile and sub-adult females, and also between sub-adult and adult females. Monthly mean values of adult male and female HSI did not significantly vary throughout the year. Significant monthly changes were recorded in mean values of adult male however no significant changes were observed in monthly mean of GSI and OSI for adult females. Vitellogenic activity and production of egg cases permanently occurred throughout the year. The diameter of largest yolky oocytes ranged from 20.1 to 23.0 (mean = 21.43 ± 1.07) and weighed from 0.64 to 0.90 g (mean = 0.78 ± 0.09). Some measurements were taken on egg cases: length with horns ranged 42.5-55.7 mm with mean = 48.9 ± 2.9, width ranged 13.6–19.7 mm with mean = 16.50 ± 0.9, while the total mass of complete egg case ranged between 1.8 and 4.6 g, with mean = 2.4 ± 0.4. An annual fecundity estimation based on production of egg cases and oocytes during one year counted in adult females, enabled us to consider it between 40 and 240.     

Age,growth and maturity of tub gurnard (Chelidonichthys lucerna Linnaeus 1758; Triglidae) in the inshore coastal waters of Northwest Wales,UK

The tub gurnard Chelidonichthys lucerna has been identified by ICES as a potential commercial species in the northeast Atlantic with recommendations made to monitor landings and discards and to derive information on population biology for stock assessment purposes, however, data are lacking for the species in the northeast Atlantic. Therefore, aims of this study were to provide data on the size/age‐structure and patterns of growth, maturity and mortality of C. lucerna in Northwest Wales, UK, and in doing so to provide data on the biological characteristics of the most northerly population studied to date for comparison with the existing data for southerly Mediterranean populations. Data on the age, growth and maturity of C. lucerna were collected by otter trawling (73 mm cod‐end stretched mesh size) in the coastal waters of Northwest Wales, UK in October (2000–2011, excluding 2006). Total length (TL) of fish sampled ranged between 10.5–41.0 cm (males) and 10.4–57.5 cm (females). The majority of the female fish were between 20–30 cm TL (60.2%) and the majority of the male fish between 20–30 cm TL (58.3%) respectively. TL/weight (W) relations for male and female fish were similar and the combined data was described by W = 0.0067 TL^3.10. Age of fish ranged between 1–7 years old for female fish and 1–5 years old for male fish respectively with the majority of female fish 3 years old (40%) and the majority of male fish 3 years old (37%). The age structures of female and male tub gurnards were not significantly different with the older age classes consisting predominantly of female fish. Both males and females exhibited similar asymptotic growth patterns and the combined von Bertalanffy growth function was TL_t = 51.6 (1 ? e ^{[?0.25(t + 0.41)]}). Instantaneous rates of total mortality were calculated as 1.04 year^?1 for males and 1.11 year^?1 for females. The size (L₅₀) and age at first maturity (A₅₀) were estimated to be 29.1 cm TL and 2.8 years for males, 27.7 cm TL and 2.7 years for females and 28.0 cm TL and 2.8 years for both sexes combined. The results of this study provide the first information on the biology and population dynamics of C. lucerna in the Irish Sea, the first data collected in the northeast Atlantic since 1985 and the most northerly population studied to date.     

Seasonal reproduction and sexual maturity in Odontocymbiola magellanica (Neogastropoda, Volutidae)

Abstract. Members of Odontocymbiola magellanica (Volutidae, Odontocymbiolinae) inhabit Argentinean waters from 35°S to the Magallanes Strait. The reproductive biology of this potential fishery resource has not been studied before. Male individuals reach maturity at 80 mm and females at 90 mm, corresponding to ∼7 and 8 years of age, respectively. Mating was observed in the field in all seasons and females possess live spermatozoa in the bursa copulatrix all year round, suggesting that living sperm can be preserved for several months. Major oviposition events occurred July (winter) to December (summer) during the 5 years sampled, as characterized by aggregation of females coincident with increasing photoperiod from winter to summer solstices, and not, apparently, by increase in water temperature. Males showed gametogenic activity throughout the year. Gamete resorption occurred in both sexes. Ultrastructural studies showed that oocytes are attached to companion cells, which enables cell–cell communication and provides support until evacuation; males showed normal sperm cells and two types of parasperms. If populations of O. magellanica are commercially exploited in the future, we propose a minimum catch size of 100 mm, and a ban on the collection of females and egg capsules during the reproductive season.     

Age and growth of Anguilla anguilla in the Camargue lagoons

Age and total length ( L _T) data from a 11 year monitoring of the Anguilla anguilla eel population of the Camargue lagoons (Rhône delta, southern France) were collected for glass, yellow and silver eels. Three distinct models were calibrated to describe the growth process of undifferentiated eels, females and males, respectively. Uncertainty of parameter estimates was evaluated by bootstrapping. Females were characterized by larger asymptotic body size ( L _T) than males (580 ± 50 v . 388 ± 13 mm) and faster growth, whilst the Brody growth coefficient was larger for males than for females (means ±  s . d . 3·00 10⁻³ ± 1·68 10⁻³ v . 1·73 10⁻³ ± 0·50 10⁻³). Sexual differentiation was estimated to begin at 204 ± 38 mm mean ±  s . d ., i.e . at the end of the second year in the lagoons, well before the L _T at which macroscopic differentiation became possible ( c . 300 mm). Males probably leave the lagoon or die (due to either natural or fishing mortality) within the first 3 years, whilst females can remain up to 5 years. Sexual differentiation and maturation have a major role in shaping the L _T structure of the population. The L _T and mass ( M ) data were fitted by allometric curves     . The calibration of distinct curves for data from different years indicated that the allometric coefficient a was subject to wider interannual fluctuations than the allometric exponent b . A negative correlation linked the average L _T and the allometric exponent ( r  = −0·58, P  < 0·01).     

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.     

Reproductive biology of racer goby Neogobius gymnotrachelus in the Włocławski Reservoir (Vistula River, Poland)

Initial studies on the reproductive parameters and spawning behaviour of racer goby Neogobius gymnotrachelus, one of three Ponto‐Caspian gobiid species recently invading Polish waters, were carried out in W?oc?awski Reservoir (lower River Vistula, Poland), where spawning lasted from April to August. Males were on average about 23.3% longer and 53.8% heavier than females. The smallest female with mature gonads was 58 mm TL (estimated age 2+ years), and males were sexually mature at 59 mm TL (age of 1+ years). Gonado‐somatic index at the beginning of spawning was seven times larger in females (mean = 8.4) than that in males (mean = 1.2). Mean absolute fecundity was 952 eggs per female (361–2236). Egg diameter ranged from 0.140 to 1.558 mm, being of bi‐modal distribution, which suggests two or three spawning bouts. Length–frequency analysis of juveniles revealed a multimodal distribution. Specialized reproductive behaviour (nest construction and parental care of eggs) and an extended spawning period increase the probability that racer goby can successfully establish self‐sustaining populations in novel environments.