Sexual differentiation and gonad development in striped mullet (Mugil cephalus L.) from South Carolina estuaries*

This study examined the sexual differentiation and reproductive dynamics of striped mullet (Mugil cephalus L.) in the estuaries of South Carolina. A total of 16,464 specimens were captured during the study and histological examination of sex and maturity was performed on a subsample of 3670 fish. Striped mullet were sexually undifferentiated for the first 12 months, began differentiation at 13 months, and were 90% fully differentiated by 15 to 19 months of age and 225 mm total length (TL). The defining morphological characteristics for differentiating males was the elongation of the protogonial germ tissue in a corradiating pattern towards the center of the lobe, the development of primary and secondary ducts, and the lack of any recognizable ovarian wall structure. The defining female characteristics were the formation of protogonial germ tissue into spherical germ cell nests, separation of a tissue layer from the outer epithelial layer of the lobe-forming ovarian walls, a tissue bud growing from the suspensory tissue that helped form the ovary wall, and the proliferation of oogonia and oocytes. Sexual maturation in male striped mullet first occurred at 1 year and 248 mm TL and 100% maturity occurred at age 2 and 300 mm TL. Female striped mullet first matured at 2 years and 291 mm total length and 100% maturity occurred at 400 mm TL and age 4. Because of the open ocean spawning behavior of striped mullet, all stages of maturity were observed in males and females except for functionally mature females with hydrated oocytes. The spawning season for striped mullet recruiting to South Carolina estuaries lasts from October to April; the majority of spawning activity, however, occurs from November to January. Ovarian atresia was observed to have four distinct phases. This study presents morpholog ical analysis of reproductive ontogeny in relation to size and age in South Carolina striped mullet. Because of the length of the undifferentiated gonad stage in juvenile striped mullet, previous studies have proposed the possibility of protandric hermaphrodism in this species. The results of our study indicate that striped mullet are gonochoristic but capable of exhibiting nonfunctional hermaphroditic characteristics in differentiated mature gonads.

Fecundity and spawning season of striped mullet (Mugil cephalus L.) in South Carolina estuaries

Fecundity in striped mullet (Mugil cephalus) from South Carolina correlated highly with length and weight, but not with age. Oocyte counts ranged from 4.47 × 105 to 2.52 × 106 in 1998 for fish ranging in size from 331 mm to 600 mm total length, 2.13 × 105to 3.89 × 106in 1999 for fish ranging in size from 332 mm to 588 mm total length, and 3.89 × 105 to 3.01 × 106 in 2000 for fish ranging in size from 325 mm to 592 mm total length. The striped mullet in this study had a high degree of variability in the size-at-age relation-ship; this variability was indicative of varied growth rates and compounded the errors in estimating fecundity at age. The stronger relationship of fecundity to fish size allowed a much better predictive model for potential fecundity in striped mullet. By comparing fecundity with other measures of reproductive activity, such as the gonadosomatic index, histological examination, and the measurement of mean oocyte diameters, we determined that none of these methods by themselves were adequate to determine the extent of reproductive development. Histological examinations and oocyte diameter measurements revealed that fecundity counts could be made once developing oocytes reached 0.400 μm or larger. Striped mullet are isochronal spawners; therefore fecundity estimates for this species are easier to determine because oocytes develop at approximately the same rate upon reaching 400 μm. This uniform development made oocytes that were to be spawned easier to count. When fecundity counts were used in conjunction with histological examination, oocyte diameter measurements, and gonadosomatic index, a more complete measure of reproductive potential and the timing of the spawning season was possible. In addition, it was determined that striped mullet that recruit into South Carolina estuaries spawn from October through April.

Observations on the artificial fertilization of eggs and larval rearing of the grey mullet, Mugil cephalus L.

The results are presented of attempts to artificially fertilize Mugil cephalus eggs in the Philippines. Embryonic development is outlined and rearing of the larvae described. Mass mortality occurred during week 3 of rearing.

Growth, recruitment, and abundance of juvenile striped mullet (Mugil cephalus) in South Carolina estuaries

Growth, recruitment, and abundance of young-of-the-year (YOY) striped mullet (Mugil cephalus L.) in estuarine habitats in South Carolina from 1998 to 2000 were examined and compared to historical data (1986–91) of growth, recruitment, and abundance. Daily growth increments from the sagittal otoliths of juvenile striped mullet were validated by using fish immersed in oxytetracycline hydrochloride (OTC) for five hours from the Charleston Harbor Estuary system. The distribution of back-calculated birthdates indicated that striped mullet spawn from October to late April and estuarine recruitment occurs from January through May. Juveniles were more abundant in mesohaline and polyhaline salinity regimes but were found throughout the estuary. Juvenile growth after recruitment into the estuary can be described by the relationship Total length (mm) = 0.341 (Age)1.04 (r2=0.741, P=0.001). Growth of juveniles according to the analysis of size-frequency data from historical surveys (1986 to 1991) in the same estuaries gave the relationship Total length (mm) = 8.77 (month)1.12 (r2=0.950, P=0.001). The similarity in the growth curves for both groups of fish suggests that juvenile striped mullet in South Carolina have consistent annual growth during the first year of life.

Aspects of the reproductive biology of Mugil cephalus (Linnaeus, 1857) in Bonny Estuary

Aspects of the reproductive biology of Mugil cephalus in the Bonny estuary (Nigeria) were studied between January and December 1996. Males were observed to be more slender than females while the females have deeper bodies. The male:female ratio (1:0:95) was not significantly different. The minimum size at maturity was 16.6cm (0.5 yr). Fish matured at 24.3cm TL(1.76 yr) with median maturity size of 19.5cm TL(0.71 yr). Median maturity for male and female fish were 16.4cm TL(0.41 yr) and 18.2cm TL(0.60 yr) respectively. Breeding occurred once a year between September and December, from late rainy season to early dry season. Mean absolute fecundity was 1,403, 808 eggs (range 107, 729-4,445, 423 eggs) for fish of 17.0.29.5cm TL (mean 22.5cm TL). Fecundity correlated positively with fish total weight, length, ovary weight and age

Age and growth of Mugil cephalus (Linnaeus, 1758) (Perciformes: Mugilidae) in Bonny Estuary

The age and growth of Mugil cephalus was investigated in Bonny Estuary, Nigeria, from January, 1995 to December, 1996. Length-weight relationships were isometric with length exponents of 2.84 (males), 2.90 (females) and 2.88 (overall). Modal length at age were 12.0cm, 20.9cm, 25.0cm, 28.4cm and 30.2cm TL for ages 0+, 1+, 2+, 3+ and 4+ respectively. Corresponding total weights were 20.01g, 78.93g, 173.12g, 217.61g and 247.50g, respectively. Asymptotic length (Lo) was estimated 33.2cm TL, asymptotic weight (W sub(o)) was 484g, growth coefficient K=0.55847 super(-1) and hypothetical age at zero length To = 0.152yr. Longevity, Tmax, was 5.0yr, length and weight growth performance indices were Q super(1)=2.79 and Q = 1.44, respectively. Total mortality, natural mortality and fishing mortality were z = 1.02yr super(-1), M=0.607yr super(-1) and F=O. 3129yr super(-1), respectively. The exploitation ratio E was 0.4048 and exploitation rate U = 0.2302yr super(-1)

Culture of grey mullet, Mugil cephalus, Linnaeus in brackishwater ponds at two stocking densities

The culture potential of hatchery-produced grey mullet (Mugil cephalus, Linnaeus) stocked with average weight of 3.7 g and at 2,500 (treatment I) and 3,000 (treatment II) fingerlings/ha in six 350m brackishwater ponds following the lab-ab method of culture was studied.

The survey of sexual maturity in Mugil cephalus so measuring sex hormones and histologic studies

In this study the process of female gray mullet brooders was carried out by using histological study and masurment of sex steroids. Results of histological studies showed that oocyte of gray mullet brooders in Gomishan Rearing Center conditions of develop to the end of yolk globule stage. The results were observed with oocyte in chromatin nucleolar stage (first stage) with means of diameter of 20 p m, in August, perinucleolar stage (second stage) in September with mean diameter of 87 p m, yolk vesicle stage (third stage) in October with mean diameter 200 p m and yolk granules stage (forth stage) from October to November with average diameter of 180 — 650 p m. For the reason of stopping oocyte develop at the end of fourth stage, hormonal induction to final oocyte maturation and ovulation was used. For this purpose, carp pituitary , HCG and LRH-A2 with different combinations were used in two stages, second injection was used 24 hours after first injection. 15 females brooders were divided in 5 groups, different hormonal combinations were injected to four groups and to fifth group as control, only saline, was injected. The process of female brooder rippening in hormonal induction was studied via masurment of sex steroids including 17 a - hydroxy progestrone, estradio1-17)6 and testosterone. Blood samples were collected from caudal vein during first injection, 24, 30 and 48 hours after the first injection. At the same time, for distinguishing histological changes the sample has been attained from the gonads Sex stroid fluctuation patterns in different brooder groups that injected hormon were similar, however hormonal composition had similar effects. All brooder that their oocyte in the beginning of hormonal injection were At the end of fourth stage with oocyte diameter average of 600 p m received to final maturation and ovulation. The brooder that its oocytes were At the begining or mid-fourth stage did not show ovulation but hormonal induction caused oocyte develop at the beginning of fifth stage. Study of 17-hydroxy progestrone fluctuation showed that the maximum level of this steroid (0.347 ng/ml) measured 30 hours after the first injection and was significantly higher (p< 0.05) than those of control group. So, 17-hydroxy progestrone is probably precursor of maturation inducing steroid (MIS). However the maximum level of that observed was coincident with germinal vesicle breakdown, oil droplets coalescence and dissolution of yolk granuls The maximum levels of esteradiol— 17/0 and testosterone (3.778 and 16.801ng/ml,respectively) in spawned brooders,were observed 24 hours after the first injection. levels of those steroids were significantly higher (p<0.05) than control group. Maximum level of sex steroids in the brooders that did not spawn to the end of treatment was observed with more delay than those in spawned brooders. Therefor maximum level of 17a-hydroxy progestrone (0.264 ng/ml) in those brooders observed in fourth sampling time and the maximum levels of estradio1-17a and testosterone (2.944 and 18.993 ng/ml, respectivly)observed in third sampling time that was significantly higher (p<0.05) than those of control group. For the study of stress effect on brooders during the hormonal induction, level of cortisol was measured in every sampling time. level of cortisol had high fluctuation that showed handling level and stress effect on brooders. However maximum level of cortisol in majority of brooders was dominant in third sampling time that was coincident with final maturation.

Aquaculture Asia, Vol.13, No.4, pp.1-51, October-December 2008

Editorial An increasingly secure future for wastewater-fed aquaculture in Kolkata, India? by Peter Edwards. First culture-based fisheries growth cycle in Lao PDR is overwhelmingly encouraging, by Sena De Silva. Revival of abandoned shrimp farms in Krishna District of Andhra Pradesh, by National Centre for Sustainable Aquaculture (NaCSA). Growth of forward and backward industries linked with aquaculture in Kolleru Lake area, Andhra Pradesh, India, by A. K. Roy, G. S. Saha, P. Kumaraiah and N. Sarangi Effective marketing strategies for economic viability of prawn farming in Kuttanad, India, by Ranjeet K. and B. Madhusoodana Kurup. Applications of nutritional biotechnology in aquaculture, by S.D. Singh, S.K. Nayak, M. Sekar and B.K. Behera. Some technical and management aspects of catfish hatcheries in Hong Ngu district, Dong Thap province, Vietnam, by H. P. Hung, N. T. T. An, N. V. Trieu, D. T. Yen, U. Na-Nakorn, Thuy T. T. Nguyen. Nodavirus: An emerging threat to freshwater prawn farming, by Biju Sam Kamalam, J., Saravanan, S. and Ajith Stalin, J.L. Asia-Pacific Marine Finfish Aquaculture Network Magazine: Asian seabass farming: Brainstorming workshop and training in India. Comparative study for broodstock management of grey mullet (Mugil cephalus L.) in cages and earthen ponds with hormone treatment, by Nani Gopal Das, Md. Shahadat Hossain, Sushanta Bhattacharjee and Prabal Barua. Cultivation of gilthead sea bream (Sparus auratus L.) in low saline inland water of the southern part of Israel desert, by Samuel Appelbaum and A. Jesu Arockia Raj. Mariculture development opportunities in SE Sulawesi, Indonesia, by La Ode M. Aslan, Hotman Hutauruk, Armen Zulham,Irwan Effendy, Mhummaed Atid, Michael Phillips, Lars Olsen, Brendan Larkin, Sena S De Silva, Geoff Gooley. Improved hatchery and grow-out technology for marine finfish. NACA Newsletter

Hubungan panjang berat dan faktor kondisi tiga jenis ikan yang tertangkap di perairan Kuala Gigieng, Aceh Besar, Provinsi Aceh

The study of the length weight relationships and condition factors of the brackishwater fishes found in Kuala Gigieng was conducted. The objective of the present study was to evaluate the growth patterns and condition factor of the belanak (Mugil cephalus), seriding (Ambassis koopsii) and petek (Leiognathus fasciatus). The sampling was conducted for eight time on July 2011 by using gillnet and castnet. The results showed that the belanak (M. cephalus) and seriding (A. koopsii) have allometric negative growth patten, while the petek (L. fasciatus) has an allometric positive. In addition, the relative weight condition factor’s was higher than 100. And the Fulton’s condition factor were not different significantly among fishes. Indicating the condition of the Kuala Gigeng is relatively in good condition and support fish growth as well.

Effect of farm made feeds on polyculture of shrimp (Penaeus monodon) and three brackishwater finfish species

A study was conducted to evaluate the effects of feed made from locally available ingredients on polyculture of shrimp and three brackishwater finfish species. Hatchery produced post-larvae (PL) of shrimp Penaeus monodon (0.005g) were stocked at the rate of 15,000 PLs/ha. Brackishwater finfish species Liza parsia, Mugil cephalus and Rhinomugil corsula of 0.63-1.4lg collected from local rivers were stocked at the rate 8,000, 1,000 and 2,000/ha, respectively in four treatments. Shrimp and finfishes were fed four different experimental diets composed of fish meal, mustard oil cake, rice bran, oyster shell power and vitamin premixes at the rate of 3-5% estimated crop/day for 195 days. Among four treatments, P. monodon showed comparative better growth in T4 and T3. Finfish L. parsia showed its better performance in treatment T2. Species M. cephalus and R. corsula showed insignificant production. P. monodon showed better growth with diet of fish meal and mustard oil cake@ 28.84 and 33.65%, respectively in T 3 and 19.22 and 43.27%, respectively in treatment T4.

Fish assemblages found in tidal-creek and seagrass habitats in the Suwannee River estuary

Fish assemblages were investigated in tidal-creek and seagrass habitats in the Suwannee River estuary, Florida. A total of 91,571 fish representing 43 families were collected in monthly seine samples from January 1997 to December 1999. Tidal creeks supported greater densities of fish (3.89 fish/m2; 83% of total) than did seagrass habitats (0.93 fish/m2). We identified three distinct fish assemblages in each habitat: winter−spring, summer, and fall. Pinfish (Lagodon rhomboides), pigfish (Orthopristis chrysoptera), and syngnathids characterized seagrass assemblages, whereas spot (Leiostomus xanthurus), bay anchovy (Anchoa mitchilli), silversides (Menidia spp.), mojarras (Eucinostomus spp.), and fundulids characterized tidal-creek habitats. Important recreational and commercial species such as striped mullet (Mugil cephalus) and red drum (Sciaenops ocellatus) were found primarily in tidal creeks and were among the top 13 taxa in the fish assemblages found in the tidal-creek habitats. Tidal-creek and seagrass habitats in the Suwannee River estuary were found to support diverse fish assemblages. Seasonal patterns in occurrence, which were found to be associated with recruitment of early-life-history stages, were observed for many of the fish species.