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

Southern Flounder

The South Carolina Department of Natural Resources published guides to many threatened animals living in the state. This guide gives information about the Southern flounder , including description, status, habitat, conservation challenges & recommendations, and measures of success

Reproductive dynamics of female spotted seatrout (Cynoscion nebulosus) in South Carolina

We describe reproductive dynamics of female spotted sea-trout (Cynoscion nebulosus) in South Carolina (SC). Batch fecundity (BF), spawning frequency (SF), relative fecundity (RF), and annual fecundity (AF) for age classes 1−3 were estimated during the spawning seasons of 1998, 1999, and 2000. Based on histological evidence, spawning of spotted seatrout in SC was determined to take place from late April through early September. Size at first maturity was 248 mm total length (TL); 50% and 100% maturity occurred at 268 mm and 301 mm TL, respectively. Batch fecundity estimates from counts of oocytes in final maturation varied significantly among year classes. One-year-old spotted seatrout spawned an average of 145,452 oocytes per batch, whereas fish aged 2 and 3 had a mean BF of 291,123 and 529,976 oocytes, respectively. We determined monthly SF from the inverse of the proportion of ovaries with postovulatory follicles (POF) less than 24 hours old among mature and developing females. Overall, spotted seatrout spawned every 4.4 days, an average of 28 times during the season. A chronology of POF atresia for water temperature >25°C is presented. Length, weight (ovary-free), and age explained 67%, 65%, and 58% of the variability in BF, respectively. Neither RF (number of oocytes/g ovary-free weight) nor oocyte diameter varied significantly with age. However, RF was significantly greater and oocyte diameter was smaller at the end of the spawning season. Annual fecundity estimates were approximately 3.2, 9.5, and 17.6 million oocytes for each age class, respectively. Spotted seatrout ages 1−3 contributed an average of 29%, 39%, and 21% to the overall reproductive effort according to the relative abundance of each age class. Ages 4 and 5 contributed 7% and 4%, respectively, according to predicted AF values

Contributions to the life history of Black Sea Bass, Centropristis striata, off the southeastern United States

Ages of black sea bass. Cenropristis striata, from the South Atlantic Bight were determined from otoliths. Analysis of marginal increments showed that annulus formation occurred in April and May. The von Bertalanffy growth equation derived from back-calculated mean standard lengths at age was It = 341 (1 - e-O.23f.l9(I+O.3010. where t is age in years and It = standard length at age. The oldest fish was age 10. Centropristi8 striata is a protogynous hermaphrodite that undergoes sex succession at ages 1 through 8. The process of sex succession is described from histological examination of the gonads. The major spawning period is from March to May, and a minor spawn occurs in September-October. Mature males and females were encountered at age 1. Fecundity estimates ranged from 17,000 in a 108 mm SL female to 1,050.000 in a 438 mm SL fish, and were significantly related to length, weight, and age. The instantaneous rate of total mortality of C. striata from catch curve analysis, ranged from 0.721 in 1978 to 1.320 in 1981 for commercial fish traps and 0.726 in 1979 to 1.430 in 1981 for hook-and-Iine gear. Petersen mark-recapture techniques were used to determine the population size of C. striata. on two shallow-water patch reefs. Conversions of these estimates to densities gave 14-125 individuals per hectare

Biology of the Whitebone Porgy, Calamus Leucosteus, in the South Atlantic bight

Whitebone porgy, Calamus leucosteus, were taken in trawl surveys over reef and non reef habitats in the South Atlantic Bight in depths of 11 to 88 m. Larger individuals were taken in greater depths. Twelve age groups can be identified with sectioned otoliths and nine using scales. Annulus formation for otoliths and scales occurs between June and July. Von Bertalanffy growth equations of Lt = 331 [1 - e-O.173' ,..,.6390IJ from otoliths and Lt = 362 [ 1- e-O.261111.0.3973] from scales suggest that attainment of maximum size for this species is similar to reports for other reef species. The fork length-weight relationship for C. leucosteus can be described by W= 0~00004 FL'·90? The whitebone porgy is a protogynous hermaphrodite; younger, smaller fish are predominately females, and older, large fish are mostly males. Sexual transition most commonly occurs between ages II-IV and fork lengths 18-25 em. Peak spawning occurs in May with total fecundity ranging from 30,400 to 1,587,400 eggs. The fecundity-weight relationship can be described by F = 10.29438 WI.6562. Regional landings data are not available for C. leucosteus; however, it was the third and fourth most abundant species by weight from trawler landings in South Carolina during 1979 and 1980

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

Staging ovaries of Haddock (Melanogrammus aeglefinus): implications for maturity indices and field sampling practices

We build on recent efforts to standardize maturation staging methods through the development of a field-proof macroscopic ovarian maturity index for Haddock (Melanogrammus aeglefinus) for studies on diel spawning periodicity. A comparison of field and histological observations helped us to improve the field index and methods, and provided useful insight into the reproductive biology of Haddock and other boreal determinate fecundity species. We found reasonable agreement between field and histological methods, except for the regressing and regenerating stages (however, differentiation of these 2 stages is the least important distinction for determination of maturity or reproductive dynamics). The staging of developing ovaries was problematic for both methods partly because of asynchronous oocyte hydration during the early stage of oocyte maturation. Although staging on the basis of histology in a laboratory is generally more accurate than macroscopic staging methods in the field, we found that field observations can uncover errors in laboratory staging that result from bias in sampling unrepresentative portions of ovaries. For 2 specimens, immature ovaries observed during histological examination were incorrectly assigned as regenerating during macroscopic staging. This type of error can lead to miscalculation of length at maturity and of spawning stock biomass, metrics that are used to characterize the state of a fish population. The revised field index includes 3 new macroscopic stages that represent final oocyte maturation in a batch of oocytes and were found to be reliable for staging spawning readiness in the field. The index was found to be suitable for studies of diel spawning periodicity and conforms to recent standardization guidelines

Contribution to the life history and reproductive biology of gag, mycteroperca microlepis (serrandidae), in the South Atlantic bight

The gag, Myceteroperca microlepis, is a demersal serranid found along the southeastern coast of the States and in the Gulf of Mexico. Throughout its range the gag is of both commercial and recreational importance. Because of its relatively slow growth rate and desirability, overfishing is of wide concern. The gag is a protogynous hermaphrodite, and suggested that sexual transformation occurs during the 10th or 11th year. Spawning occurs from January to March off the west coast of Florida , and the maximum reported age is 13 years in both the Gulf of Mexico and the South Atlantic Bight 1978 J. Microscopic examination of the gonads is necessary for definite sexual identification, but gonad morphology has not been specifically described. The purpose of this study is to provide new information on the age, growth. and reproductive biology of this important species, including a description of the morphology of gag ovaries and testes