Age and growth of sailfish (Istiophorus platypterus) in waters off eastern Taiwan

Age and growth of sailfish (Istiophorus platypterus) in waters off eastern Taiwan were examined from counts of growth rings on cross sections of the fourth spine of the first dorsal fin. Length and weight data and the dorsal fin spines were collected monthly at the fishing port of Shinkang (southeast of Taiwan) from July 1998 to August 1999. In total, 1166 dorsal fins were collected, of which 1135 (97%) (699 males and 436 females) were aged successfully. Trends in the monthly mean marginal increment ratio indicated that growth rings are formed once a year. Two methods were used to back-calculate the length of presumed ages, and growth was described by using the standard von Bertalanffy growth function and the Richards function. The most reasonable and conservative description of growth assumes that length-at-age follows the Richards function and that the relationship between spine radius and lower jaw fork length (LJFL) follows a power function. Growth differed significantly between the sexes; females grew faster and reached larger sizes than did males. The maximum sizes in our sample were 232 cm LJFL for female and 221 cm LJFL for male.

Multidirectional movements of sportfish species between an estuarine no-take zone and surrounding waters of the Indian River Lagoon, Florida

We examined movement patterns of sportfish that were tagged in the northern Indian River Lagoon, Florida, between 1990 and 1999 to assess the degree of fish exchange between an estuarine no-take zone (NTZ) and surrounding waters. The tagged f ish were from seven species: red drum (Sciaenops ocellatus); black drum (Pogonias cromis); sheepshead (Archosargus probatocephalus); common snook (Centropomus undecimalis); spotted seatrout (Cynoscion nebulosus); bull shark (Carcharhinus leucas); and crevalle jack (Caranx hippos). A total of 403 tagged fish were recaptured during the study period, including 65 individuals that emigrated from the NTZ and 16 individuals that immigrated into the NTZ from surrounding waters of the lagoon. Migration distances between the original tagging location and the sites where emigrating fish were recaptured were from 0 to 150 km, and these migration distances appeared to be influenced by the proximity of the NTZ to spawning areas or other habitats that are important to specific life-history stages of individual species. Fish that immigrated into the NTZ moved distances ranging from approximately 10 to 75 km. Recapture rates for sportfish species that migrated across the NTZ boundary suggested that more individuals may move into the protected habitats than move out. These data demonstrated that although this estuarine no-take reserve can protect species from fishing, it may also serve to extract exploitable individuals from surrounding fisheries; therefore, if the no-take reserve does function to replenish surrounding fisheries, then increased egg production and larval export may be more important mechanisms of replenishment than the spillover of excess adults from the reserve into fishable areas.

Larval development of the southern sea garfish (Hyporhamphus melanochir) and the river garfish (H. regularis) (Beloniformes: Hemiramphidae) from South Australian waters

Larval development of the southern sea garfish (Hyporhamphus melanochir) and the river garfish (H. regularis) is described from specimens from South Australian waters. Larvae of H. melanochir and H. regularis have completed notochord flexion at hatching and are characterized by an elongate body with distinct rows of melanophores along the dorsal, lateral, and ventral surfaces; a small to moderate head; a heavily pigmented and long straight gut; a persistent pre-anal finfold; and an extended lower jaw. Fin formation occurs in the following sequence: caudal, dorsal and anal (almost simultaneously), pectoral, and pelvic. Despite the similarities between both species and among hemiramphid larvae in general, H. melanochir larvae are distinguishable from H. regularis by 1) having 58–61 vertebrae (vs. 51–54 for H. regularis); 2) having 12–15 melanophore pairs in longitudinal rows along the dorsal margin between the head and origin of the dorsal fin (vs. 19–22 for H. regularis); and 3) the absence of a large ventral pigment blotch anteriorly on the gut and isthmus (present in H. regularis). Both species can be distinguished from similar larvae of southern Australia (other hemiramphids and a scomberosocid) by differences in meristic counts and pigmentation.

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.

Age, growth, and reproduction of permit (Trachinotus falcatus) in Florida waters

We examined 536 permit (Trachinotus falcatus, 65–916 mm FL) collected from the waters of Florida Keys and from the Tampa Bay area on Florida’s Gulf coast to describe their growth and reproduction.Among permit that we sexed, females ranged from 266 to 916 mm in length (mean=617) and males ranged from 274 to 855 mm (mean=601). Ages of 297 permit ranging from 102 to 900 mm FL were estimated from thin-sectioned otoliths (sagittae). The large proportion of otoliths with an annulus on the margin and an otolith from an OTC-injected fish suggested that a single annulus was formed each year during late spring or early summer.Permit reach a maximum age of at least 23 years.Permit grew rapidly until an age of about five years, and then growth slowed considerably. Male and female von Bertalanffy growth models were not significantly different, and the sexes-combined growth model was FL=753.1(1–e –0.348(Age+0.585)). Gonad development was seasonal, and spawning occurred during late spring and summer over artificial and natural reefs at depths of 10–30 m. Ovaries that contained oocytes in the final stages of oocyte maturation or postovulatory follicles were found during May–July. We estimated that 50% of the females in the population had reached sexual maturity by 547 mm and an age of 3.1 years and that 50% of the males in the population had reached sexual maturity by 486 mm and an age of 2.3 years. Because Florida regulations restrict the maximum size of permit caught in recreational and commercial fisheries to 20-inch (508-mm), most fish harvested are sexually immature. With the current size selectivity of the fishery, the spawning stock biomass of permit could decrease quickly in response to moderate levels of fishing mortality; thus, the regulations in place in Florida to restrict harvest levels appear to be justified.

Reproduction of blacknose shark (Carcharhinus acronotus) in coastal waters off northeastern Brazil

The blacknose shark, Carcharhinus acronotus, is a relatively small carcharinid, typically inhabiting continental shelf areas in the western Atlantic Ocean, from North Carolina throughout the Gulf of Mexico (Bigelow and Schroeder, 1948) and along the South American coast to Rio de Janeiro (Compagno, 1984). The abundance of this shark in nearshore areas throughout its distribution makes it accessible to commercial fishing, mainly from inshore hook-and-line and gill-net fisheries (Trent et al., 1997; Mattos and Hazin1).

Age, growth, mortality, and distribution of pinfish (Lagodon rhomboides) in Tampa Bay and adjacent Gulf of Mexico waters

Life-history dynamics of pinfish (Lagodon rhomboides) were examined from data derived from random station surveys conducted in Tampa Bay and adjacent Gulf of Mexico waters during 1993–97. In addition, patterns in spatial distribution and abundance in Gulf of Mexico waters were investigated. Ages determined from whole otoliths ranged from 0 to 7 years, and von Bertalanffy growth models for males and females were not significantly different. Von Bertalanffy growth model parameters were L∞=219.9 mm SL, k =0.33/yr, and t0 =–1.10 years for all fish combined. High gonadosomatic indices during October–December indicated that some spawning may occur in Tampa Bay. Estimated lengths at 50% maturity were 132 mm SL for males and 131 mm SL for females. Total instantaneous mortality rates derived from the Chapman-Robson estimator ranged from 0.88 to 1.08/yr, and natural mortality was estimated to be 0.78/yr. In Gulf of Mexico waters, pinfish catch rates declined with increasing depth, and most pinfish were caught in <17 m of water. Length distributions showed that pinfish segregate by size with increasing depth.

Age and growth of the swordfish (Xiphias gladius L.) in the waters around Taiwan determined from anal-fin rays

Age and growth of the swordfish (Xiphias gladius) in Taiwan waters was studied from counts of growth bands on cross sections of the second ray of the first anal fin. Data on lower jaw fork length and weight, and samples of the anal fin of male and female swordfish were collected from three offshore and coastal tuna longline fishing ports on a monthly basis between September 1997 and March 1999. In total, 685 anal fins were collected and 627 of them (293 males and 334 females) were aged successfully. The lower jaw fork lengths of the aged individuals ranged from 83.4 to 246.6 cm for the females and from 83.3 to 206 cm for the males. The radii of the fin rays and growth bands on the cross sections were measured under a dissecting microscope equipped with an image analysis system. Trends in the monthly marginal increment ratio indicated that growth bands formed once a year. Thus, the age of each fish was deter-mined from the number of visible growth bands. Two methods were used to estimate and compare the standard and the generalized von Bertalanffy growth parameters for both males and females. The nonlinear least square estimates of the generalized von Bertalanffy growth parameters in method II, in which a power function was used to describe the relationship between ray radius and LJFL, were recommended as most acceptable. There were significant differences in growth parameters between males and females. The growth parameters estimated for females were the following: asymptotic length (L∞) = 300.66 cm, growth coefficient (K) = 0.040/yr, age at zero length (t0) = –0.75 yr, and the fitted fourth parameter (m) = –0.785. The growth parameters estimated for males were the following: asymptotic length (L∞) = 213.05 cm, growth coefficient (K) = 0.086/yr, age at zero length (t0) = –0.626 yr, and the fitted fourth parameter (m) = –0.768.

Studies on the occurrence of coliforms and streptococci in coastal waters of Bombay

The distribution of coliforms and streptococci in Bombay coastal waters was investigated in order to determine the state of pollution in the area. Findings show the incidence of pollution to be of a recurring nature, primarily due to discharge of raw or improperly treated sewage; thus regular monitoring of the incidence of coliforms and streptococci is of importance in determining the public health safety of the beaches and coastal waters.