Biology of two commercially important carcharhinid sharks from northern Australia

1986 ◽  
Vol 37 (6) ◽  
pp. 671 ◽  
Author(s):  
JD Stevens ◽  
PD Wiley
Keyword(s):  
Stomach Contents ◽  
Size At Maturity ◽  
Northern Australia ◽  
Gill Net ◽  
Average Litter Size ◽  
Commercially Important ◽  
Mature Fish ◽  
Reproductive Cycles ◽  
Size At Birth ◽  
Pelvic Fin

Sharks represent 78% of the total catch by weight of a Taiwanese surface gill-net fishery off northern Australia. Two carcharhinids, Carcharhrnus tilstoni (previously described as C. limbatus) and C. sorrah, together comprise 83% of this shark catch by number. C. tilstoni is distinguished from C. limbatus by differences in enzyme systems, vertebral counts, size data and pelvic fin coloration. Of the specimens of C. tilstoni and C. sorrah caught in the Arafura and Timor Seas from 1981 to 1983, 43% and 47%, respectively, were female; at birth these proportions were 46% and 50%, respectively. In both species, females tended to be relatively more abundant in catches of mature fish, except around March, when males predominated. In northern Australia, the usual size at maturity for C. tilstoni is 110 cm for males and 115 cm for females; for C. sorrah, it is 90 cm and 95 cm, respectively. Both species exhibit placental viviparity and have almost identical restricted reproductive cycles. Mating occurs in February-March, ovulation in March-April and the main parturition period is in January. The gestation period is 10 months and individual fish breed each year. The average litter size for both species is three. The size at birth is about 60 cm for C. tilstoni and 50 cm for C. sorrah. Stomach contents indicate that teleost fish are an important component of the diet of both species and there is some indication of a change in feeding depth with shark size.

Biology of three hammerhead sharks (Eusphyra blochii, Sphyrna mokarran and S. lewini) from Northern Australia

1989 ◽  
Vol 40 (2) ◽  
pp. 129 ◽  
Author(s):  
JD Stevens ◽  
JM Lyle
Keyword(s):  
Litter Size ◽  
Adult Female ◽  
Seasonal Cycle ◽  
Size At Maturity ◽  
Northern Australia ◽  
Gill Net ◽  
Form Part ◽  
Incidental Catch ◽  
Hammerhead Sharks ◽  
Size At Birth

The hammerhead sharks Eusphyra blochii, Sphyrna mokarran and S. lewini form part of the incidental catch of a commercial gill-net fishery off northern Australia. Of the specimens sampled between June 1980 and December 1986, 46% of S. mokarran, 41% of E. blochii and 31% of S. lewini were females. Few adult female S. lewini were caught and it is suggested that these occur offshore of the study area. In northern Australia, the usual size at maturity of male E. blochii, S. lewini and S. mokarran is 108, 150 and 225 cm total length (TL), ,and of females is 120, 200 and 210 cm TL, respectively. S. mokarran and E. blochii gave birth in January and February/March, respectively, after a gestation period of 10-11 months. S. Iewini appears to have a more extended seasonal cycle: the young are born between October and January after 9-10 months gestation. Size at birth is about 45-50 cm TL in E. blochii and S. lewini, and 65 cm TL in S. mokarran. Mean litter size is 12 in E. blochii, 15 in S. mokarran and 17 in S. lewini. Individual E. blochii females breed every year, whereas S. mokarran females probably breed every other year. Fish are an important component of the diet of all three species as, to a lesser extent, are cephalopods for S. lewini and crustaceans for S. mokarran and E. blochii.

Gill-net mesh selectivities for two species of commercial carcharhinid shark taken in northern Australia

1994 ◽  
Vol 45 (4) ◽  
pp. 521 ◽  
Author(s):  
KJ McLoughlin ◽  
JD Stevens
Keyword(s):  
Gamma Distribution ◽  
Distribution Model ◽  
Northern Australia ◽  
Gill Net ◽  
Commercially Important

Experiments designed to estimate gill-net mesh selectivities for two species of commercially important sharks in northern Australia were carried out between 1983 and 1984. A gamma distribution model was used to obtain length-specific selectivities for Carcharhinus tilstoni and C. sorrah caught in nets with stretched-mesh sizes of 10, 15, 20 and 25 cm. Captured sharks were categorized as gilled or rolled (tangled) in the nets. The model provided a better fit to the data for C. sorrah than for C. tilstoni.

Movements, recapture patterns, and factors affecting the return rate of carcharhinid and other sharks tagged off northern Australia

2000 ◽  
Vol 51 (2) ◽  
pp. 127 ◽  
Author(s):  
J. D. Stevens ◽  
G. J. West ◽  
K. J. McLoughlin
Keyword(s):  
Fishing Effort ◽  
Return Rate ◽  
Maximum Distance ◽  
Northern Australia ◽  
Factors Affecting ◽  
Gill Net ◽  
Commercially Important ◽  
Inshore Waters ◽  
Made In ◽  
Tag Shedding

Between February 1983 and May 1985, ~10 500 sharks of 23 species were fin-tagged off northern Australia. Tagging concentrated on the commercially important Carcharhinus tilstoni and C. sorrah. Most recaptures were made in 1984 and 1985, but returns continued until May 1997. In all, 579 tags (5.5%) were recovered. Tag shedding was estimated to be low (0.025 year –1 for C. tilstoni) and tagging mortality was significantly lower for sharks caught by hand-line than by gill-net. Australian gill-netters, Taiwanese gill-netters (fishing in the Australian Fishing Zone) and Australian prawn trawlers accounted for most of the returns. The maximum distance between the release and recapture positions was >1100 km, but most returns were made within 50 km of the tagging site. Nearly all the releases were in inshore waters fished by Australian vessels. Although many recaptures were made by the offshore Taiwanese fishery, the Taiwanese fishing effort was much higher than for the inshore Australian fishery, so that relative to fishing effort, relatively few sharks moved from inshore to offshore waters.

Diet of three commercially important shark species from Western Australian waters

2001 ◽  
Vol 52 (7) ◽  
pp. 975 ◽  
Author(s):  
Colin A. Simpfendorfer ◽  
Adrian Goodreid ◽  
Rory B. McAuley
Keyword(s):  
Stomach Contents ◽  
Shark Species ◽  
Rock Lobster ◽  
Gill Net ◽  
Wide Range ◽  
Carcharhinus Obscurus ◽  
Commercially Important ◽  
Specialized Diet ◽  
Western Australian ◽  
Benthic Prey

The diets of dusky (Carcharhinus obscurus), whiskery (Furgaleus macki) and gummy (Mustelus antarcticus) sharks from south-western Western Australia were examined by analysis of stomach contents. The majority of samples were obtained from catches of commercial gill-net fishers. Carcharhinus obscurus had a diverse diet dominated by pelagic teleosts and cephalopods. A wide range of demersal and benthic prey were also consumed, but represented only a small portion of the diet. As body size increased, importance of elasmobranchs in the diet of C. obscurus increased, while most other groups remained at similar levels. Furgaleus macki had a specialized diet, feeding almost exclusively on octopus and other cephalopods. The diet of M. antarcticus was dominated by benthic and epibenthic prey, including crabs, lobsters, tetraodontid fishes and octopus. As M. antarcticus increased in size there was an increase in the occurrence of rock lobster and a decrease in the occurrence of crabs in the diet. Differences in the diet were also noted between male and female M. antarcticus, but were confounded with differences between size classes.

Pollen treatment for mutation induction in Eucalyptus globulus ssp. globulus (Myrtaceae)

2006 ◽  
Vol 54 (1) ◽  
pp. 65 ◽  
Author(s):  
L. J. McManus ◽  
J. Sasse ◽  
C. K. Blomstedt ◽  
G. Bossinger
Keyword(s):  
Tree Species ◽  
Eucalyptus Globulus ◽  
Frost Tolerance ◽  
Mutation Induction ◽  
Crop Species ◽  
Integral Role ◽  
Fruit Abortion ◽  
Commercially Important ◽  
Reproductive Cycles ◽  
Short Time

Mutation induction has played an integral role in the improvement of most commercially important crop species but has not been successfully applied to tree species because of their long reproductive cycles which hinder the use of the traditional seed-treatment approaches. Treatment of pollen with a chemical mutagen prior to pollination will, theoretically, allow stable, heterozygous mutant trees to be produced in a relatively short time and might facilitate mutagenesis of tree species. As the first step in testing this hypothesis, a controlled-pollination trial with chemically treated pollen was conducted in Eucalyptus globulus ssp. globulus (Labill.). Assessment of fruit, seed and seedlings from more than 500 pollinations associated mutagenic treatment of pollen with a significant reduction in seed set. Non-significant increases in capsule (fruit) abortion, the inhibition of seed germination and the incidence of aberration in seedlings were also noted. We argue that pollen treatment may be a useful means of producing Eucalyptus mutants with variation in flowering time, salinity and frost tolerance, lignification and other traits of scientific and economic importance.

scholarly journals Stomach Content of Tillapia zilli and Oreochromis nilocticus from Wanzun River, Lavun Local Government, Niger State Nigeria

2021 ◽  
pp. 15-20
Author(s):  
Y. M. Mohammed ◽  
M. D. Abubakar ◽  
A. M. Muhammad ◽  
A. S. Muhammad ◽  
B. L. Umar ◽  
...  
Keyword(s):  
Fish Species ◽  
Stomach Content ◽  
Stomach Contents ◽  
Empty Stomach ◽  
Plant Materials ◽  
Individual Fish ◽  
Fish Samples ◽  
Commercially Important ◽  
Fish Remains ◽  
The One

This study was conducted to investigate the stomach contents of two commercially important fish species (Tilapia zilli and Oreochromis nilocticus)  from Wanzun River, Northcentral Nigeria using frequency of occurrence and volumetric methods between January to April 2019. Fish samples were collected monthly with help of Fishermen using various fishing nets and traps. One hundred (100) individual fish of each species were collected and their stomach contents were examined. The results obtained expressed in mean percentage indicated that out of the one hundred (100) individual fish of each species examined,Twelve (12%) fish had an empty stomach contents in Tilapia zilli, and out of the 100 samples examined, Seventeen (17%) fish had an empty stomach content in Oreochromis nilocticus. The stomach contents of both Tilapia zilli and Oreochromis nilocticus consist of detritus, insects, fish remains. Algae/protozoans plant materials and molluscs. Both fish species are omnivorous feeders and occupy the same ecological niche.The study reveals the importance of algae, fish, insects and plant materials as food for fishes and they form important part in the diet of the species examined.

scholarly journals Food Habits and Diet Relationship in the Redbelly Tilapia (Tilapia zillii) and Guenther’s Mouthbrooder (Chromidotilapia guntheri) from an Abandoned Gold Mine Reservoir, Southwestern Nigeria

2018 ◽  
Vol 10 (2) ◽  
pp. 148-155
Author(s):  
Olusola Olaniyi KOMOLAFE ◽  
Timothy Olalekan AMOO ◽  
Michael Olufemi AWODIRAN
Keyword(s):  
Feeding Habits ◽  
Stomach Contents ◽  
Food Sources ◽  
Gold Mine ◽  
Southwestern Nigeria ◽  
Food Items ◽  
Tilapia Zillii ◽  
Gill Net ◽  
Food And Feeding ◽  
Index Value

The food and feeding habits of the redbelly Tilapia (Tilapia zillii) and Guenther’s mouthbrooder (Chromidotilapia guntheri) were investigated in an abandoned gold mine reservoir at Igun from June 2013 to May 2014. Using a cast net and gill-net fishing gears, 370 fish individuals were caught and their stomach contents were analysed by using the frequency of occurrence and numerical methods. Tilapia zillii comprised 53.78% (199 individuals), while Chromidotilapia guntheri covered up the remaining percentage (46.22%) which is made up of 171 individuals. Food items in the stomachs of T. zillii individuals predominantly consisted of detritus, mud and algae (77.97%), while those in C. guntheri individuals mostly consisted fish remains, detritus and algae (81.67%). T. zillii exploited more food items (23 of 27) as compared to C. guntheri (17 of 27). The Schoener’s index value for the species was 0.65. The study showed that T. zillii and C. guntheri exhibited benthopelagic exploitation and are mainly herbivorous and omnivorous respectively based on the food items observed in the stomach contents of these species. The fish species fed on related food items as confirmed by Schoener’s overlap index (0.65), suggesting that there was overlap in the dietary requirements of the two species. This index value, however, was probably not an indication of competition for food between these two species because they exploited abundant food sources.

scholarly journals Catch assessment of artisanal marine fishing gears in Cox’s Bazar and Teknaf of Bangladesh

2016 ◽  
Vol 27 (2) ◽  
pp. 228-234
Author(s):  
SK Ghosh ◽  
MK Ahsan ◽  
MK Ahmmed ◽  
SI Ahmed ◽  
MM Hasan ◽  
...  
Keyword(s):  
Fish Species ◽  
Fishing Gear ◽  
Catch Per Unit Effort ◽  
Beach Seine ◽  
Gill Net ◽  
Fishing Gears ◽  
Dominant Fish ◽  
Commercially Important ◽  
Marine Fishing ◽  
Harpadon Nehereus

Studies were conducted on catch assessment of some artisanal marine fishing gears operated in Cox’s Bazar and Teknaf areas from April 2014 to April 2015. Sixteen types of fishing gears were identified, of which gill net, beach seine net, estuarine set bag net, marine set bag net and trammel net occupy major fishing activities. Although estuarine set bag net (ESBN) is a legally restricted fishing gear recorded the highest catch per unit effort (CPUE) (110 kg/gear/day) in July followed by marine set bag net (MSBN) (105 kg/gear/day) in Cox’s Bazar and the highest CPUE was recorded 100 kg/gear/day by ESBN in June followed by MSBN (90 kg/gear/day) in Teknaf. Out of 52 species of fishes, the major fish species abundantly caught by these gears were Poa (Otolithoides argenteus), Churi (Trichiurus haumela), Loittya (Harpadon nehereus), Ranga choukha (Lutjanus johni), Lal poa (Johnius argentatus), Olua (Coilia dussumieri), Rup chanda (Stromateus chinensis), (Stromateus argenteus) and Ilish (Tenualosa ilisha). Besides these fish species, 10 commercially important shrimp species and 3 important crab species were also recorded during the study period. The peak season of availability of most fish species was June and July while lean season was December and January. This study indicated that Otolithoides argenteus) was the dominant fish species followed by Trichiurus haumela, Harpadon nehereus and Coilia dussumieri.Progressive Agriculture 27 (2): 228-234, 2016

Distribution, size and sex composition, reproductive biology and diet of sharks from Northern Australia

1991 ◽  
Vol 42 (2) ◽  
pp. 151 ◽  
Author(s):  
JD Stevens ◽  
KJ McLoughlin
Keyword(s):  
Sex Ratio ◽  
Reproductive Biology ◽  
Annual Cycle ◽  
Post Partum ◽  
Austral Summer ◽  
Size Composition ◽  
Maximum Size ◽  
Northern Australia ◽  
Average Size ◽  
Size At Birth

The distribution, size composition, sex ratio, reproductive biology and diet of 17 species of shark from the families Triakidae, Hemigaleidae and Carcharhinidae from northern Australia were examined. In most of these species the sex ratio of the embryos is 1 : 1, whereas in the post-partum populations there were significantly more males than females. The results indicate four broad reproductive strategies among these sharks. In most species reproduction was distinctly seasonal with individual females giving birth each Austral summer (annual cycle) after a gestation period of 9-12 months. A second group had a very similar cycle except that individual females gave birth every second year (biennial cycle). A third group had an annual cycle but breeding was continuous throughout the year, these were mostly small bottom-associated sharks. One species had a seasonal cycle but gave birth twice each year (biannual cycle) after a 6-month gestation. The average size at birth varied from 27 to 75 cm and the average litter size varied from 2 to 34. The size at birth was about 40% of the size at maturity, which in turn was about 70% of the maximum size. Diets ranged from omnivorous to highly selective. Fish was an important component of the diet in all but one species. There was evidence of partitioning of food resources among sympatric, morphologically similar, sharks.

Reproductive characteristics and per-recruit analyses of blue warehou (Seriolella brama): implications for the South East Fishery of Australia

2001 ◽  
Vol 52 (4) ◽  
pp. 575 ◽  
Author(s):  
Ian A. Knuckey ◽  
K. P. Sivakumaran
Keyword(s):  
Egg Production ◽  
East Coast ◽  
Gonadosomatic Index ◽  
Fork Length ◽  
Size At Maturity ◽  
Current Management ◽  
Spawning Period ◽  
Gill Net ◽  
Trawl Fishing

Monthly samples of commercial catches of S. brama were collected between May 1996 and December 1997 in three regions of the fishery:off the east coast of Victoria; eastern Tasmania; and western Bass Strait. Sex ratio, gonadosomatic index, macroscopic and histological development, size at maturity and fecundity were estimated and combined with data on growth and mortality to perform per-recruit analyses. The main spawning period was during winter–spring and there was evidence of spawning in each of the three regions. Blue warehou reach maturity at 30–40 cm fork length. They have a determinate annual fecundity and spawn around three batches of eggs during a season. Eggs-per-recruit analyses revealed maximum egg production at ~40 cm (4–5 years) in an unfished population. Gill-net fishing, which targets fish >45 cm, was less likely to affect the relative eggs-per-recruit in a population than trawl fishing, which catches a wider range of smaller fish. These results are discussed in light of the current management arrangements in the fishery and will be used in models to assess the effect of fishing on the long-term sustainability of the blue warehou.

Sign in / Sign up

Export Citation Format

Share Document