Reproductive seasonality, fecundity, and spawning frequency of tautog (Tautoga onitis) in the lower Chesapeake Bay and coastal waters of Virginia

The tautog, Tautoga onitis (Linnaeus), ranges from Nova Scotia to South Carolina and has become a popular target for recreational and commercial fisheries. Although tautog are a multiple spawning species, reproductive potential, measured as annual fecundity, has not been estimated previously with methods (batch fecundity, spawning frequency) necessary for a species with indeterminate annual fecundity. A total of 960 tautog were collected from the mouth of the Rappahannock River in the lower Chesapeake Bay to 45 km offshore of Virginia’s coastline to investigate tautog reproductive biology in the southern portion of the species range. Tautog did not exhibit a 1:1 sex ratio; 56% were females. Male tautog reached 50% maturity at 218 mm TL, females at 224 mm TL. Tautog spawned from 7 April 1995 to 15 June 1995, at locations from the York River to 45 km offshore. Batch fecundity estimates ranged from 2800 to 181,200 eggs per spawning for female tautog age 3–9, total length 259– 516 mm. Mean batch fecundity ±SEM for female tautog ages 4–6 was 54,243 ±2472 eggs and 106,256 ±3837 eggs for females ages 7–9. Spawning frequency was estimated at 1.2 days, resulting in 58 spawning days per female in 1995. Estimates of potential annual fecundity for tautog ages 3–9 ranged from 160,000 to 10,510,000 eggs.

Reproductive biology of the blue swimmer crab (Portunus pelagicus, Decapoda: Portunidae) in five bodies of water on the west coast of Australia

Portunus pelagicus was collected at regular intervals from two marine embayments and two estuaries on the lower west coast of Australia and from a large embayment located approximately 800 km farther north. The samples were used to obtain data on the reproductive biology of this species in three very different environments. Unlike females, the males show a loosening of the attachment of the abdominal flap to the cephalothorax at a prepubertal rather than a pubertal molt. Males become gonadally mature (spermatophores and seminal fluid present in the medial region of the vas deferentia) at a very similar carapace width (CW) to that at which they achieve morphometric maturity, as reflected by a change in the relative size of the largest cheliped. Logistic curves, derived from the prevalence of mature male P. pelagicus, generally had wider confidence limits with morphometric than with gonadal data. This presumably reflects the fact that the morphometric (allometric) method of classifying a male P. pelagicus as mature employs probabilities and is thus indirect, whereas gonadal structure allows a mature male to be readily identified. However, the very close correspondence between the CW50’s derived for P. pelagicus by the two methods implies that either method can be used for management purposes. Portunus pelagicus attained maturity at a significantly greater size in the large embayment than in the four more southern bodies of water, where water temperatures were lower and the densities of crabs and fishing pressure were greater. As a result of the emigration of mature female P. pelagicus from estuaries, the CW50’s derived by using the prevalence of mature females in estuaries represent overestimates for those populations as a whole. Estimates of the number of egg batches produced in a spawning season ranged from one in small crabs to three in large crabs. These data, together with the batch fecundities of different size crabs, indicate that the estimated number of eggs produced by P. pelagicus during the spawning season ranges from about 78,000 in small crabs (CW=80 mm) to about 1,000,000 in large crabs (CW=180 mm).

Age and size composition, growth rate, reproductive biology, and habitats of the West Australian dhufish (Glaucosoma hebraicum) and their relevance to the management of this species

Samples of the commercially and recreationally important West Australian dhufish (Glaucosoma hebraicum) were obtained from the lower west coast of Australia by a variety of methods. Fish <300 mm TL were caught over flat, hard substrata and low-lying limestone reefs, whereas larger fish were caught over larger limestone and coral reef formations. Maximum total lengths, weights, and ages were 981 mm, 15.3 kg, and 39 years, respectively, for females and 1120 mm, 23.2 kg, and 41 years, respectively, for males. The von Bertalanffy growth curves for females and males were significantly different. The values for L∞, k, and t0 in the von Bertalanffy growth equations were 929 mm, 0.111/year, and –0.141 years, respectively, for females, and 1025 mm, 0.111/year, and –0.052 years, respectively, for males. Preliminary estimates of total mortality indicated that G. hebraicum is now subjected to a level of fishing pressure that must be of concern to fishery managers. Glaucosoma hebraicum, which spawns between November and April and predominantly between December and March, breeds at a wide range of depths and is a multiple spawner. The L50’s for females and males at first maturity, i.e. 301 and 320 mm, respectively, were attained by about the end of the third year of life and are well below the minimum legal length (MLL) of 500 mm. Because females and males did not reach the MLL until the end of their seventh and sixth years of life, respectively, they would have had, on average, the opportunity of spawning during four and three spawning seasons, respectively, before they reached the MLL. However, because G. hebraicum caught in water depths >40 m typically die upon release, a MLL is of limited use for conserving this species. Alternative approaches, such as restricting fishing activity in highly fished areas, reducing daily bag limits for recreational fishermen, introducing quotas or revising specific details of certain commercial hand-line licences (or doing both) are more likely to provide effective conservation measures.

The reproductive biology of the porbeage shark (Lamna nasus) in the western North Atlantic Ocean

Reproductive organs from 393 male and 382 female porbeagles (Lamna nasus), caught in the western North Atlantic Ocean, were examined to determine size at maturity and reproductive cycle. Males ranged in size from 86 to 246 cm fork length (FL) and females ranged from 94 to 288 cm FL. Maturity in males was best described by an inflection in the relationship of clasper length to fork length when combined with clasper calcification. Males matured between 162 and 185 cm FL and 50% were mature at 174 cm FL. In females, all reproductive organ measurements related to body length showed a strong inflection around the size of maturity. Females matured between 210 and 230 cm FL and 50% were mature at 218 cm FL. After a protracted fall mating period (September–November), females give birth to an average of 4.0 young in spring (April−June). As in other lamnids, young are nourished through oophagy. Evidence from this study indicated a one-year reproductive cycle and gestation period lasting 8–9 months.

Reproductive engineering in crustacean aquaculture

Crustacean aquaculture industry in India suffers greatly from lack of technological developments. A major constraint in this enterprise is the limitation of seed stock availability. A critical appraisal is made of the techniques used in the manipulation of reproductive processes in order to augment year-round production of seeds. A new possibility of induced ovarian maturation in crustaceans is by administering steroid hormones of vertebrate source. Environmental factors are known to govern the gametogenic cycle of marine crustaceans. Cryopreservation of male gametes and artificial insemination by way of spermatophore transfer could solve some of the problems of mating under laboratory conditions.

Reproductive biology of Parapenaeopsis stylifera

Controversy exists regarding the incidence and reproductive habits of Parapenaeopsis stylifera along the coast of Kerala, India. Results are reported of a detailed study on the different aspects of the reproductive biology based on the trawl catches landed at Neendakara Coast for a period of one year. This species breeds throughout the year with peak breeding activity in May and November. The monsoon catches consist of juveniles. Life span of the species is 2.5 years and total length at first maturity is 75 mm. Measures for the effective management of the species in the area are discussed.

Some aspects of reproductive biology of two sciaenids, Otolithes cuvieri Trewavas and Johnius elongatus Mohan: maturation, spawning, sex ratio and fecundity

The gonads of Otolithes cuvieri and Johnius elongatus are described in seven maturity stages. O. Cuvieri spawns once a year from April to September as evidence by ova diameter frequency distribution and GSI values. 50% maturity is attained at 210mm TL in males and 200mm TL in females. Fecundity ranged from 2387 to 104379 with a mean value of 33502. Log-Log relationship between fecundity and total lenght, body weight and ovary weight were determined. An overall sex ratio of 1.54:1.00 was unequal in favour of males. Johnius elongatus spawns twice a year from January-February to Aprile-May and from August to October as evidence by ova diameter frequency distribution and GSI values. 50% maturity is attained at 140-143mm TL in both sexes. Fecundity ranged from 4238 to 167669 with a mean value of 42818. Log-Log relationship between fecundity and total lenght, body weign and ovary weight were determined. An overall sex ratio of 1.00:1.20 was unequal in favour of females.

A study of the male reproductive organs of nine species of penaeid prawns (Crustacea: Penaeinae)

This paper deals with the male reproductive organs of nine species of penaeid prawns; Penaeus penicillatus Alcock, P. merguiensis De Man, P. semisulcatus De Haan, Metapenaeus affinis (H.Milne Edwards), M. monoceros (Fabricius), M. stebbingi Nobili, Parapenaeopsis hardwickii (Miers), P. sculptilis (Heller) and P. stylifera (H. Milne Edwards). The male reproductive organs exhibited structural variations, which were more pronounced at generic level. These variations are mainly due to the type of spermatophore they possess. One species of each genus, that is, P. merguiensis, M. affinis and P. sculptilis were also studied histologically to examine the internal structure of the male reproductive organs. Spermatophores of the six species belonging to the genera Penaeus and Parapenaeopsis are also described and illustrated.

Reproductive biology of the blue spot mullet Valamugil seheli (Forskal) from Mangalore Region, southwest coast of India

The blue spot mullet Valamugil seheli spawns once a year between August and February with peak spawning during October - November. Males attain maturity at 250.5 mm and females at 256.5 mm total length. Males outnumbered females in the commercial catches, although the sex-ratio (M:F=1:0.90) in the population showed no significant deviation. The fecundity of this species varied from 108378 to 910350 eggs with an average of 327944. Linear relationships were found between fish length, gonad weight and fecundity; and between fish length, fish weight and ovary weight.

Reproductive biology of Otolithes cuvieri (Trewavas, 1974) from Mumbai waters

The reproductive biology of Otolithes cuvieri (Trewavas, 1974) is reported in the present communication. The size at first maturity for the females was estimated to be 275 mm. The spawning activity was observed throughout the year with two peaks occurring in April and June. Two prominent peaks of gonadosomatic index (April and June) also support the view of two major spawning. Relative fecundity ranged from 71,574 to 79,680 eggs per 100g of body weight. Relationship of fecundity with fish length, fish weight and ovary weight of the species has been established as F = -132971 + 1447.441 x L, F = 124195 + 468.798 x W and F = 250517.5 + 3369.029 x OW, respectively. Study of sex ratio by random sampling of the catches indicated the dominance of females in commercial catches of Mumbai coast.