Comparing three methods to estimate the average size at first maturity: A case study on a Curimatid exhibiting polyphasic growth

The average size at first |maturity (L₅₀) is among the most important parameters for fisheries management and conservation. This paper aims to compare three different methods for its estimation. Considering a classical approach, a logistic model was used (a) by determining the gonadal stage macroscopically; and (b) by using the GSI as proxy of sexual maturity; and finally; (c) by using the length–weight relationship (LWR) in a theoretical approach. The proposed methods were applied using data of a detritivorous fish, Cyphocharax abramoides, monthly sampled using gill nets. Captured individuals were measured, weighed, sexed and the gonadal stage was classified macroscopically and weighed. Estimated L₅₀ values using the macroscopic identification, GSI approach and LWR were not different from each other considering confidence intervals. Between the three different techniques, we concluded that the analysis of the LWR in fishes with polyphasic growth presented promising results as it only requires length and weight data to be performed and estimate a L₅₀ within the range of both classical logistic models analysed.     

Modelling individual variability in growth of bull trout in the Walla Walla River Basin using a hierarchical von Bertalanffy growth model

We examined growth in length of fluvial bull trout (Salvelinus confluentus) in the Walla Walla River Basin, Washington and Oregon. Our objectives were to quantify individual variability in growth; examine growth within and among years, life history forms, life stages and sexes; and estimate von Bertalanffy growth parameters. Individual variability was evaluated by modelling asymptotic length (L_∞) and the growth coefficient (k) as random variables. All models were fit with Bayesian methods and were evaluated for fit by the deviance information criterion. By incorporating individual variability, population‐level estimates of L_∞ and k appeared appropriate and estimated growth trajectories for specific bull trout fit individual observed patterns in growth. Growth trajectories and positive correlation between individual estimates of L_∞ and k suggest that some individuals grow at a faster rate and reach a larger maximum size than other individuals and those differences are maintained throughout life. Selected models suggest that fluvial migrants have higher estimates of L_∞ and k than residents, but there were only slight differences in parameter estimates among migrants from two adjacent spawning populations in the Walla Walla River Basin, as well as between males and females. Growth rates increased for fluvial migrants after subadult emigration. Individual variability in growth is consistent with the life history diversity assumed essential for bull trout population persistence. Quantifying this variability is important for modelling population dynamics and viability to conserve this threatened species.     

Analysis of growth, weight and relevant indices of diploid and triploid population of tench Tinca tinca (Linnaeus 1758)

This study determined biometric and weight parameters and relevant indices of diploid and triploid tench. Altogether, 137 siblings of tench were studied. The effect of ploidy level appeared in significantly better growth of triploids (P<0.001) as to biometric [total length (TL), standard length (SL), body height (BH), body width (BW)] and weight [fish weight (FW), carcass weight (CW)] parameters of T₃ of both sexes and of T₃₊ females. The effect of ploidy level also appeared as significantly higher dressing percentage (DP; P<0.001) of triploid T₃ females compared with other groups, significantly higher gonad weight (GW) and gonadosomatic index (GSI; P<0.001) of diploid T₃ females, as well as GSI and hepatosomatic index of diploid T₃₊ females. The effect of sex appeared in significantly higher (P<0.001) biometric (TL, SL, BH, BW) and weight (FW, CW) parameters of T₃ females of both ploidy levels, as well as of triploid T₃₊ females. The effect of sex also appeared as significantly higher DP (P<0.001) of males in diploid T₃ fish, as well as of males of both ploidy levels in T₃₊ fish and significantly higher GW and GSI (P<0.001) of females in diploid T₃ fish, as well as of females of both ploidy levels in T₃₊ fish. This study shows evidence for faster somatic growth and bigger final weight of triploid populations of tench compared with diploids in both age categories T₃ and T₃₊.     

Age and growth of the largemouth perch Percichthys colhuapiensis in the Negro river, Argentine Patagonia

Largemouth perch (Percichthys colhuapiensis) represents one of the most economically important fish species in the Argentine Patagonia. However, little research has been done on the age and growth and population dynamics of this fish, though both studies are essential to properly deal with fisheries forecasts and management. As a contribution to elaborating management programmes for P. colhuapiensis, we evaluated the age and growth of this species in the Negro river via scale and whole otolith reading methods. The sample consisted of 579 specimens ranging in total length (TL) from 90 to 475 mm, captured seasonally from December 1994 to December 1995. The formation of scale annuli (end of winter) and the hyaline zone on otoliths (winter) of adult fish coincided with the beginning of the spawning season (end of winter-beginning of spring). The maximum estimated age was 11 years, which indicates that this is a relatively long-lived species. Otoliths were useful for ageing specimens 1–5 years-old, but above this age whole otoliths yielded lower age estimates than scales. Isometric growth of weight with length was found for total population, juveniles, and separate sexes (p > 0.25 in all cases). No significant differences between the length–weight relationships of sexes were observed (p > 0.10). Length at first maturity was significantly higher for males (TL₅₀ = 271 mm TL; r = 0.88) than for females (TL₅₀ = 243 mm TL; r = 0.96) (p < 0.01). Largemouth perch exhibited a consistent pattern of increase in length with age, with a period of fast growth during the first 5 years, and a slow-growing phase during the rest of his life. The growth parameters based on scale data were L∞: 462.1 mm, k = 0.23 and t₀ = −0.94 for total population, L∞: 402.3 mm, k = 0.33 and t₀ = −0.67 for males, and L∞: 548.4 mm, k = 0.15 and t₀ = −1.59 for females, whereas those based on otolith reading were L∞: 537.4 mm, k = 0.17 and t₀ = −1.0 for total population, L∞: 497.6 mm, k = 0.21 and t₀ = −0.79 for males, and L∞: 582.0 mm, k = 0.14 and t₀ = −1.53 for females. Scales are concluded to be the best structure to age P. colhuapiensis because they rendered L∞ values closer to the maximum TL observed, high precision, easiness of collection, low processing time, and the possibility of performing non-destructive monitoring studies.     

Size at maturity for grooved Tanner crab (Chionoecetes tanneri) along the U.S. west coast (Washington to California)

We conducted a multiyear study to examine interannual variability in the mean size (carapace width, mm), maturity size (mm) and depth (m) for grooved Tanner crab (Chionoecetes tanneri (Rathbun, 1893)) along the U.S. west coast. An additional goal was to provide updated estimates of carapace width (mm) at 50% maturity (W₅₀) for male and female grooved Tanner crab and assess changes over time. Randomly selected samples came from trawl surveys undertaken annually by the Northwest Fisheries Science Center at depths of 55 to 1280 m. We used allometric relationships between carapace width (CW) and either abdominal width (AW) (females) or chela length (CL) (males) to determine functional maturity by sex. We evaluated maturity by fitting logistic regression models to proportion mature grooved Tanner crab. W₅₀ varied significantly between males (125.2 mm) and females (89.1 mm) but interannual differences were slight. The annual mean CW were greater for mature males (139.9–143.4 mm) relative to females (98.8–100.4 mm). The average sizes of immature grooved Tanner crab varied between sexes with males (75.7–84.6 mm) larger than females (66.7–71.9 mm). Size frequency distributions indicated little overlap in the size of mature male and female grooved Tanner crab but considerable overlap between immature grooved Tanner crab. The best model expressing complexity in growth incorporated width, sex and maturity stage. Depth ranged from 195–1254 m with the average depth of a mature grooved Tanner crab (females, 737 m; males, 767 m) significantly shallower than an immature (females, 949 m; males, 918 m) grooved Tanner crab.     

Decreasing shrimp (Pandalus borealis) sizes off Newfoundland and Labrador – environment or fishing?

During the 1990s, carapace length statistics including minimum size caught (L_min), mean male and female lengths, size at sex transition (L₅₀) and maximum size (L_max) of northern shrimp (Pandalus borealis) decreased in commercial and survey catches off Newfoundland and Labrador. Decreased growth rates caused by decreases in per‐capita food availability due to large population increases, exacerbated by increased metabolic demands from higher water temperatures in the mid‐1990s, appear to be the main cause of the size decrease. Fishing could have had an accelerating effect on environmentally driven decreases in shrimp growth and size by ‘cropping’ the largest shrimp from the population. The greatest decreases in shrimp size occurred in Hudson Strait and the adjacent northern shelf, the area which also has the highest densities and largest shrimp. We hypothesize that the greater size decrease here resulted from decreased primary production from decreased nutrient flux into the euphotic zone, caused by increased atmospheric warming, freshwater runoff and stratification during the warming trend of the 1990s.     

Growth,sex ratio,and maturation rate with age in the blackspot tuskfish <Emphasis Type="Italic">Choerodon schoenleinii</Emphasis> in waters off Okinawa Island,southwestern Japan

The growth, sex ratio with age, and age at sexual maturation were determined based on sectioned otoliths in 257 specimens of the blackspot tuskfish Choerodon schoenleinii collected in waters off Ryukyu Island. Opaque rings observed by reflected light in the sectioned otoliths were found to form once a year from January to July. The three growth parameters of the von Bertalanffy growth equation were L_∞ = 68.1 (cm), k = 0.263, and t ₀ = −0.023 (year). The age at which the sex ratio reached 50% by sexual transition was about 6.15 years, and the age at which 50% of females were sexually mature was approximately 2 years. The oldest specimen among the samples was 17 years old.     

Trait‐related variation in the reproductive characteristics of female pikeperch (Sander lucioperca)

Maternal characteristics typically affect the recruitment of an exploited fish population. The size and age at maturity, as well as the effects of maternal traits on relative fecundity and egg dry weight, were studied in six exploited pikeperch populations in Finnish lakes. The among‐lake variation in the maternal characteristics was substantial. The estimated total length at maturity (L₁₀, L₅₀, L₉₀) varied between 318–444, 403–423 and 444–527 mm, respectively, largely depending on the average growth rate and body condition of pikeperch. The estimated L₅₀ was generally close to the recently imposed national minimum size limit (42 cm). The estimated age at maturity (A₅₀) ranged from 4.2 to 6.9 year. Both relative fecundity and egg dry weight significantly increased with female size and age, indicating size‐ and age‐dependent maternal effects on egg characteristics and quantity, and emphasising the importance of large individuals for reproduction. The observed among‐population differences in the size‐dependent maternal influences highlight the need for stock‐specific management of pikeperch fisheries. The conservation of large females should be promoted to increase recruitment and reduce its variability.     

Reproductive biology of pink dentex Dentex gibbosus (Rafinesque) from the Adriatic Sea, Croatia

A 4‐year study (May 1997–December 2000) of the reproductive biology of pink dentex Dentex gibbosus (Rafinesque) from the Adriatic Sea revealed that this species is a rudimentary hermaphrodite. The smallest mature males and females captured were 38.70 cm in total length (T_L) and 39.80 cm in total length (T_L) respectively. The von Bertalanffy growth parameters estimated for the entire population were: L_∞=107.24, K=0.12 and t₀=−0.90. Fifty per cent of the population were sexually mature at 41.50 cm T_L, while 100% of the specimens were sexually mature at 57.00 cm T_L. Both monthly gonadosomatic index and macroscopically determined gonad stages strongly indicate that the pink dentex from the Adriatic Sea spawn partially in August, September and October. The mean value of absolute fecundity (F) was 1672 × 10⁶ eggs. The results of great fertility of the pink dentex, partial spawning and relatively late sexual maturation suggest that the pink dentex has a high potential for commercial culture.     

Growth,diet, and reproduction of Eurasian perch <Emphasis Type="Italic">Perca fluviatilis</Emphasis> L. in Lake Varese,northwestern Italy

No data have previously been reported on Eurasian perch Perca fluviatilis L. in Lake Varese. In this study, the growth, diet, and reproductive biology of the Eurasian perch population were investigated with the aim of providing information that may serve as a basis for efficient resource management. A total of 240 specimens were caught during the monthly sampling campaign from November 2006 through October 2008. The length-to-weight relationships were W _t = 8.4 × 10⁻³ L _t^3.10 (males) and W _t = 4.1 × 10⁻³ L _t^3.36 (females). The parameters for the von Bertalanffy growth function for pooled sexes were L _∞  = 33.17 cm, k = 0.20 year⁻¹, and t ₀ = −1.34 year. Perch in Lake Varese spawn from April through May. Sexual maturity is reached when males are 2 years old, in females mostly when they are 3 years old. Relative fecundity (F _rel) and absolute fecundity (F _abs) were assessed for females. Fecundity values were similar to data reported for other European populations: females of age 2+ F _rel = 102,457 ± 12,275, age 3+ F _rel = 131,767 ± 5,891, and age 4+ F _rel = 131,252 ± 15,555. Perch diet spectrum was wide and somewhat characterized by season. Perch in Lake Varese feed on macroinvertebrates, mainly Chironomidae and Chaoborus, zooplankton, and juvenile rudd Scardinius erythrophthalmus.     

The Effect of Photoperiod on Sexual Maturation,Appetite and Growth in Wild Atlantic Cod (Gadus morhua L.)

An experiment was conducted to examine (a) the effects of photoperiod on timing of sexual maturation (b) the relationship between plasma steroid levels, appetite and growth in male and female Atlantic cod (Gadus morhua L.). Wild caught Norwegian coastal cod were subjected to either a 6L/18D photoperiod typical of January at 60° N-(Short day group) or a simulated natural photoperiod (Normal day group) from June 2000 until spawning started. Appetite of individual fish were measured twice weekly, while weight, length and plasma levels of the sex steroids testosterone (T), 11 keto-testosterone (11-KT) and estradiol-17β (E2) were monitored bimonthly. Cod in the Short day group matured 3 months ahead of the cod in the Normal day group and started spawning in early November. Appetite decreased in both sexes 2–3 months prior to spawning in both groups, but this reduction was stronger among males. In both sexes, length growth was reduced concurrently with the appetite loss. Overall, females had significantly higher somatic growth, put relatively less energy into length growth and had developed larger livers compared to males at the time of spawning in the Short day group. Plasma steroid levels increased in both groups throughout the experiment, reaching peak levels of ca 10 ng ml⁻¹ (T) and 15–20 ng ml⁻¹ (11-KT) in males, and 1.5–2 ng ml⁻¹ (T) and 12–18 ng ml⁻¹ (E2) in females at the onset of spawning. Steroid levels increased more rapidly among Short day cod verifying the earlier onset of maturation. These results confirm that photoperiod is a major cue to maturation in cod and imply that the high cost of spawning for females incur differences in appetite between the sexes.     

Effects of immersion of larvae in oestradiol-17β on feminization, structural changes of gonad and growth performance in the Far Eastern catfish Silurus asotus (Linnaeus)

Immersion of 1‐day‐old Silurus asotus (Linnaeus) larvae in 50, 100 or 200 μg L^?1 oestradiol‐17β for 15 days altered gonad differentiation and gonadal morphology. The survival of the group immersed at the highest dose (200 μg L^?1) was reduced significantly (86%), whereas survival of the groups immersed at the lower doses was as high as that of untreated controls (94%). The sex ratio of the untreated group was close to 1:1 (female–male); however, the incidence of females was significantly higher in groups immersed in doses of 50, 100 and 200 μg L^?1, i.e. 86%, 92% and 99.4%, respectively. Ovarian morphology of feminized individuals was different to that of the controls; the ovary was morphologically rather similar to testis although it contained fully matured oocytes. Morphological changes in genital organs were also noted in fish exposed to oestradiol‐17β the shape and size of genital papilla were intermediate between those of normal male and female. During a 4‐month growth trial after the exposure, the feminized fish showed significantly improved growth performance over normal genetic males (P < 0.05), although the growth was not equal to that of normal genetic females (P < 0.05).     

Performance of Penaeus paulensis (Pérez-Farfante) broodstock under long-term exposure to ammonia

The effects of total ammonia (TAN; NH₄⁺+ NH₃) on the reproductive performance, survival, growth and moulting of wild Penaeus paulensis (Pérez-Farfante) broodstock were studied to determine optimal rearing conditions. Based on previously established ‘safe levels’ for P. paulensis adults (3.4 and 4.2 mg L^?1 TAN), two 46-day trials were performed. In the first trial, six females and four males were stocked in 700-L tanks under three treatments (0.37, 2.53 and 6.86 mg L^?1 TAN) with at least two replicates per treatment. In trial 2, ammonia levels of 0.68, 1.55 and 2.62 mg L^?1 TAN were assigned to three 6000-L tanks, each stocked with 36 females and 24 males. Ammonia only influenced the survival of females and the growth of males exposed to 6.86 mg L^?1 TAN (0.21 mg L^?1 NH₃). No further effects of ammonia on moulting and reproductive performance were detected. The present results demonstrate that up to 2.62 mg L^?1 TAN, coupled with 0.07 mg L^?1 NH₃ and 1.50 mg L^?1 NO₂, will not impair reproductive performance of P. paulensis. It is suggested that water quality for the maturation of P. paulensis may be maintained through lower daily water exchange rates instead of the usual high levels (150-300%) employed on penaeid shrimp maturation systems.     

Length–weight relationship and growth performance of different life stages of hatchery‐produced magur,Clarias magur (Hamilton, 1822)

Length–weight relationship (LWR) of 661 numbers of hatchery‐produced magur, Clarias magur of all the life stages such as hatchlings, fry, fingerlings, juveniles and adults, was studied. The LWR of all the life stages of magur was estimated and the equations are as follows, hatchlings W = 0.0052*L^1.282 (r² = 0.8784), fry W = 0.0088*L^3.028 (r² = 0.8113), fingerlings W = 0.0065*L^3.226 (r² = 0.8906), juveniles W = 0.0028*L^3.420 (r² = 0.8175) and adults W = 0.0017*L^3.491 (r² = 0.8310). A positive allometric growth (b > 3) was observed in all the life stages except hatchlings. The annual growth rate of magur was observed with the body length and weight of 24 ± 1 cm and 115 ± 17 g, respectively, under the commercial production system. This is the first kind of study that describes about the LWR and growth performance of all the life stages of hatchery‐produced C. magur catfish from hatchlings to adults under commercial production system. This study will be more useful to the hatchery managers and fish growers to optimize the resources and husbandry practices to improve the growth, survival, and biomass production.     

Spatial variability in the somatic growth of pikeperch Sander lucioperca,an invasive piscivorous fish

Introduced fishes can develop invasive populations that impact native species and ecosystems. Understanding the population ecology of introduced species in their extended ranges and how this compares to their native ranges is therefore important for informing their management. Here, the age and somatic growth rates of the piscivorous freshwater fish pikeperch Sander lucioperca were analysed across their invasive and native ranges to determine their spatial patterns and drivers. Analyses were initially completed in their invaded range in central and western England. Populations varied spatially in their growth rates; being slowest for a population in a narrow and shallow canal and fastest in a large, impounded lowland river. A meta‐analysis of parameters of the von Bertalanffy growth model then revealed that across their native and invasive ranges, their theoretical ultimate lengths (L_∞) and growth coefficients (K) were significantly related to latitude, but not longitude. Their relationships with latitude were nonlinear, with higher values of L_∞ and lower values of K being evident towards their northerly and southerly range limits. Faster growth rates were evident in the middle of their range (45 to 55°N), suggesting temperatures here were most optimal for growth, but were in a trade‐off with reduced ultimate lengths. These spatial patterns suggest that whilst introduced S. lucioperca can colonise new waters across a wide area, the expression of their life‐history traits will vary spatially, with potential implications for how invasive populations establish and integrate into native fish communities.     

Effects of Estradiol and Testosterone on the Expression of Growth‐related Genes in Female and Male Nile Tilapia,Oreochromis niloticus

Nile tilapia exhibits strong sexual growth dimorphism. The potential role of sex steroid hormones in sexual growth dimorphism is not fully understood. We investigated the effects of estradiol (E₂) and testosterone (T) on growth rate, plasma sex hormones, and expression of growth hormone (GH)‐insulin‐like growth factor (IGF) axis genes and muscle regulatory factor (MRF) genes in female and male Nile tilapia. The results revealed that serum concentrations of E₂ and T were significantly higher after correlative injection (P < 0.05). Compared to male fish, female fish had lower growth rates. E₂ increased growth performance in females with no significant effects on males, whereas T significantly increased growth performance in males, with no significant effects on females. In females, E₂ significantly increased expression of ghr1, ghr2, igf1, and igf2, while T decreased igf2 and increased ghr1 and ghr2 expression. In males, T increased expression of igf1, igf2, ghr1, and ghr2, and E₂ decreased expression of igf1, ghr1, and ghr2. Additionally, E₂ and T enhanced the expression of MRF genes (myod1, myod2, myog, and myf5) in female and male fish, respectively. The results suggest that sex steroid hormones play a role in sexual growth dimorphism by regulating the expression of GH‐IGF axis and MRF genes.     

大黄鱼性别特异SNP标记的开发与验证

大黄鱼是我国养殖量最大的海水经济鱼类,其雌鱼生长显著快于雄鱼,但两性的外部形态差异不明显,也没有异形性染色体,依靠传统方法无法对其活体准确进行生理性别和遗传性别的判别与鉴定,需要开发性别特异的分子标记。本研究从2尾雌鱼和2尾雄鱼、以及分别由50雌鱼与50尾雄鱼组成的2个混合样品的基因组重测序数据比较中筛选与性别显著关联的SNP位点,对其中11个位点分别设计引物在15尾雌鱼和15尾雄鱼中扩增出PCR产物进行Sanger测序验证,鉴定出1个与性别完全连锁的位点(SNP6,15尾雌鱼均为纯合、15尾雄鱼均为杂合)。然后,设计等位基因特异性PCR引物,其中包括2条雌性与雄性通用引物和1条雄性特异引物,在闽—粤东族与岱衢族大黄鱼合计近2 200个个体中进行扩增,结果在全部雌鱼中都只扩增出1个348 bp的条带,而在全部雄鱼中还扩增出1个194 bp的Y染色体特异条带,检出率达到100%。研究表明,大黄鱼属于XX♀-XY♂类型的性别决定。本研究鉴定出一个雄性特异SNP标记,并建立了一种新的大黄鱼遗传性别鉴定技术,为大黄鱼单性育种、基因组选择育种和性别决定分子机制研究提供了重要的技术手段。     

Effects of Natural EstradioI-17β and Synthetic 17α- Ethynylestradiol on Direct Feminization of European Sea Bass Dicentrarchus labrax

To produce a monosex female population of European sea bass Dicentrarchus labrax, fry were fed dry diets containing dosages of 12.5, 25, and 50 mg/kg food of either the natural estrogen estradiol-170β(E₂) or the synthetic estrogen 17α-ethynylestradiol (EE₂) for 60 d starting at 88 d post-hatch (dph). A complete feminization (100%) was achieved in all E₂-treated groups at the age of 11 mo (330 dph). All affected fish had ovaries similar in size and histological structure to those of control females. In the E₂-treated groups, feminized fish were heavier and longer than untreated controls (males and females combined). In control groups females exhibited significantly higher body weight and total length than males. Untreated females from control groups and females from the group treated with E₂ at 12.5 mg/kg food had similar body weight, suggesting that in sea bass growth is related to phenotypic sex. In the Entreated groups, survival rates were similar to those of the control fish. A relatively high percentage of females was obtained in the EE₂-treated groups (from 38.6 to 96.5%). However, the gonadal development in these fish was significantly suppressed and a dose-dependent reduction of gonadal sizes was evident. Treatments with the EE₂ (12-5, 25, and 50 mg/kg food) resulted in many fish having abnormal (2.9-5.4-39.8%, respectively) and sterile (0.6-6.0-21.6%, respectively) gonads. Effects also included significantly lower weight and shorter length when compared with controls. Furthermore, fish fed with EE₂ at the dosage of 50 mg/kg food had high mortality rate. A simple protocol was developed for the complete feminization in sea bass in which the fry (80-100 dph) were fed to satiation two times daily with a diet containing 12.5 me of E₂/ks food for a period of 60 d.     

Age,growth, maturity,and sex changes of monogrammed monocle bream Scolopsis monogramma in the waters around Okinawa-jima Island,Japan

Age, growth, maturity, and sex changes of the monogrammed monocle bream Scolopsis monogramma were estimated from ca. 500 specimens collected at Okinawa-jima Island in southern Japan. Age was determined from sectioned otoliths: maximum ages were 10 years for females and 9 years for males. Parameters for von Bertalanffy growth functions were L _t  = 206.6{1 ? exp[?0.68(t + 0.81)]} (n = 337) for females and L _t  = 244.4{1 ? exp[?0.93(t + 0.32)]} (n = 130) for males. The spawning season was estimated to last from June to July, with a peak in July. The standard length (SL) and age at 50 % maturity for females were estimated as 186.4 mm SL and 3.3 years, respectively. Intersex individuals appeared from 159.6 to 237.5 mm SL (n = 16) in fish between 1 and six years old, with the highest frequencies occurring at 170 mm SL and 2 years old. Hence, almost all S. monogramma specimens found at Okinawa-jima Island exhibited pre-maturational sex change, although some may have been protogynous hermaphrodites. Biological characteristics such as age at growth, maturation, and spawning season are valuable factors that can inform the resource management of local fisheries.