Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Reproductive biology of horse mackerel Trachurus capensis and Trachurus trecae in Namibia and Angola

Reproductive biology of horse mackerel Trachurus capensis and Trachurus trecae in Namibia and Angola Harvest control measures for Namibia and Angola are defined using reference points for spawning biomass, which requires knowledge of spawning potential and dynamics of fishery stocks. The reproductive biology of two species of horse mackerel, Trachurus capensis and Trachurus trecae, in these waters was investigated for spawning distribution in time and space. Samples were collected during two scientific cruises conducted in February and July/August 2007 off the coast of Namibia and Angola. A total of 396 fish ovaries was examined to determine the spawning dynamics of the two species. The ovaries were histologically analysed and their oocyte distributions mapped. The length (TL)–weight relationships of the two species differed significantly. The observed development of oocyte recruitment and absence of a hiatus in the oocyte distribution indicated that these species are indeterminate spawners. Analyses of the data from the NatMIRC database (2001–2004) indicated annual changes in gonadosomatic index (GSI) for T. capensis at different latitudes, but these changes were small. GSI also fluctuated between years and areas, but there were no clear spatial or temporal trends, with averages ≤4.0% at all stations. The GSI of both species was not indicative of the histologically determined development of gonad maturity. Oocyte maturation for T. capensis indicated that smaller and younger fish spawn first. Batch fecundity (F) for T. trecae was best described by F = 4 986 TL (cm) – 99 645 (r 2 = 0.83). This study provided the first analyses of oocyte development in time and space for the two species in the region. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png African Journal of Marine Science Taylor & Francis

Reproductive biology of horse mackerel Trachurus capensis and Trachurus trecae in Namibia and Angola

Download PDF

Reproductive biology of horse mackerel Trachurus capensis and Trachurus trecae in Namibia and Angola

Abstract

Harvest control measures for Namibia and Angola are defined using reference points for spawning biomass, which requires knowledge of spawning potential and dynamics of fishery stocks. The reproductive biology of two species of horse mackerel, Trachurus capensis and Trachurus trecae, in these waters was investigated for spawning distribution in time and space. Samples were collected during two scientific cruises conducted in February and July/August 2007 off the coast of Namibia and Angola. A...
Loading next page...
 
/lp/taylor-francis/reproductive-biology-of-horse-mackerel-trachurus-capensis-and-kmNG6oK1wr
Publisher
Taylor & Francis
Copyright
Copyright NISC (Pty) Ltd
ISSN
1814-2338
eISSN
1814-232X
DOI
10.2989/1814232X.2013.805595
Publisher site
See Article on Publisher Site

Abstract

Harvest control measures for Namibia and Angola are defined using reference points for spawning biomass, which requires knowledge of spawning potential and dynamics of fishery stocks. The reproductive biology of two species of horse mackerel, Trachurus capensis and Trachurus trecae, in these waters was investigated for spawning distribution in time and space. Samples were collected during two scientific cruises conducted in February and July/August 2007 off the coast of Namibia and Angola. A total of 396 fish ovaries was examined to determine the spawning dynamics of the two species. The ovaries were histologically analysed and their oocyte distributions mapped. The length (TL)–weight relationships of the two species differed significantly. The observed development of oocyte recruitment and absence of a hiatus in the oocyte distribution indicated that these species are indeterminate spawners. Analyses of the data from the NatMIRC database (2001–2004) indicated annual changes in gonadosomatic index (GSI) for T. capensis at different latitudes, but these changes were small. GSI also fluctuated between years and areas, but there were no clear spatial or temporal trends, with averages ≤4.0% at all stations. The GSI of both species was not indicative of the histologically determined development of gonad maturity. Oocyte maturation for T. capensis indicated that smaller and younger fish spawn first. Batch fecundity (F) for T. trecae was best described by F = 4 986 TL (cm) – 99 645 (r 2 = 0.83). This study provided the first analyses of oocyte development in time and space for the two species in the region.

Journal

African Journal of Marine Science – Taylor & Francis

Published: Aug 1, 2013

Keywords: batch fecundity; gonadosomatic index; indeterminate spawner; oocyte diameter; spawning area; spawning time

References

  • Horse mackerel survey methodology 07–19 October 1998. Cruise Reports Dr Fridtjof Nansen
  • Cruise Reports Dr Fridtjof Nansen
  • Horse mackerel survey of the northern Benguela (16°30′S–25°00′S) 4–27 February 2003
  • Scientific report on horse mackerel (Trachurus trachurus capensis) for 2004
  • Horse mackerel Trachurus capensis TAC Report
  • Batch fecundity in multiple spawning fishes
  • Measurements of spawning frequency in multiple spawning fishes
  • A summary of the fishery and biology of Cape horse mackerel in Namibian waters
  • Investigations into some important fish larvae in the South East Atlantic in relation to the hydrological environment
  • A transboundary study of the pelagic fish stocks of southern Angola and northern Namibia