Free Standard AU & NZ Shipping For All Book Orders Over $80!
Register      Login
Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences
Shopping Cart: ( empty )
You are here: Home > Journals > MF > MF08221
RESEARCH ARTICLE
Contents Vol 60(8)

Reducing impacts of trawling on protected sea snakes: by-catch reduction devices improve escapement and survival

David A. Milton A B , Gary C. Fry A and Quinton Dell A
+ Author Affiliations
- Author Affiliations

A Wealth from Oceans Flagship, CSIRO Marine and Atmospheric Research, PO Box 120, Cleveland, Qld 4163, Australia.

B Corresponding author. Email: david.milton@csiro.au

Marine and Freshwater Research 60(8) 824-832 https://doi.org/10.1071/MF08221
Submitted: 29 July 2008  Accepted: 20 February 2009   Published: 27 August 2009

Abstract

Sea snakes (Hydrophidae) are by-catch of prawn trawling throughout the tropical Indo-western Pacific. We tested the effectiveness of three by-catch reduction device (BRD) types set at different distances from the codend in Australia’s Northern Prawn Fishery (NPF). Trained crew-member observers compared the numbers of sea snakes caught in paired Control and Treatment nets in 1365 trawls. Catches of sea snakes were reduced by 43% on those vessels where a Fisheye BRD was positioned less than 70 meshes from the codend. A separate study with a scientific observer undertook trials with a ‘popeye’ Fishbox BRD. This BRD reduced sea snake catch by 85% and small fish by-catch by 48%. Catches of target prawn were similar for all nets in both studies (difference <2%). Adoption of the more effective BRDs (‘popeye’ Fishbox or Fisheye BRDs) by the NPF and locating them within 70 meshes of the codend can potentially reduce sea snake catch and thus their mortality from ~7000 in the 2007 fishing season to as few as 1500 snakes. Our study shows that the use of BRDs in tropical coastal demersal fisheries and positioning them closer to the codend will greatly reduce the catch of vulnerable sea snakes.

Additional keywords: management, mitigation, prawn trawling, survival.


Acknowledgements

We thank all the crew member observers who participated in the program. We especially thank Jim Yarrow for his innovation to develop and trial new BRDs during his commercial fishing. We thank Don Heales and Ted Wassenberg and two anonymous referees for constructive comments on earlier versions of the manuscript. The project was jointly funded by the Fisheries Research and Development Corporation (Project 2005/051) and CSIRO.


References

Brewer, D. , Rawlinson, N. , Eayres, S. , and Burridge, C. (1998). An assessment of bycatch reduction devices in a tropical Australian prawn trawl fishery. Fisheries Research 36, 195–215.
| Crossref | GoogleScholarGoogle Scholar | Brewer D. T., Griffiths S., Heales D. S., Zhou S., Tonks M., et al. (2007). Design, trial and implementation of an integrated, long-term bycatch monitoring program, road tested in the Northern Prawn Fishery. FRDC Project 2002/035 Final Report, CSIRO, Cleveland.

Broadhurst, M. K. (2000). Modifications to reduce bycatch in prawn trawls: a review and framework for development. Reviews in Fish Biology and Fisheries 10, 27–60.
| Crossref | GoogleScholarGoogle Scholar | Chambers J. M., and Hastie T. J. (Eds) (1992). ‘Statistical Models.’ (S. Wadsworth & Brooks/Cole Advanced Books Software: Pacific Grove, CA.)

Courtney A. J., Haddy J. A., Campbell M. J., Roy D. P., Tonks M. L. et al. (2007). Bycatch weight, composition and preliminary estimates of the impact of bycatch reduction devices in Queensland’s trawl fishery. FRDC 2000/170 Final Report.

Frid, A. , Baker, G. G. , and Dill, L. M. (2008). Do shark declines create fear-released systems? Oikos 117, 191–201.
| Crossref | GoogleScholarGoogle Scholar | Heatwole H. (1975). Sea snakes of the Gulf of Carpentaria. In ‘Biology of Sea Snakes’. (Ed. W. A. Dunson.) pp. 145–149. (University Park Press: Baltimore, MD.)

Heatwole, H. (1978). Adaptations of marine snakes. American Scientist 66, 594–604.
|  CAS | PubMed | Heatwole H. (1999). ‘Sea Snakes’. (Krieger Publishing: Malabar, FL.)

Madsen, N. , Skeide, R. , Breen, M. , Krag, L. A. , and Huse, I. , et al. (2008). Selectivity in a trawl codend during haul-back operations – an overlooked phenomenon. Fisheries Research 91, 168–174.
| Crossref | GoogleScholarGoogle Scholar | Milton D. A., Zhou S., Fry G., and Dell Q. (2008). Risk assessment and mitigation for sea snakes caught in the Northern Prawn Fishery. FRDC Project 2005/051 Final Report.

Minton S. A. (1975). Geographic distributions of sea snakes. In ‘The Biology of Sea Snakes’. (Ed. W. A. Dunson.) pp. 21–31. (University Park Press: Baltimore, MD.)

Raudzens E. (2006). At sea testing of ‘Popeye’s Fishbox’ bycatch reduction device onboard the FV Adelaide Pearl for approval in Australia’s Northern prawn Fishery. Australian Fisheries Management Authority: Canberra. Available at http://www.afma.gov.au/fisheries/northern_trawl/northern_prawn/publications/docs/other/popeyebrdreport.pdf [Accessed 9 January 2009].

Roberts, C. M. , and Hawkins, J. P. (1999). Extinction risk in the sea. Trends in Ecology & Evolution 14, 241–246.
| Crossref | GoogleScholarGoogle Scholar | Walpole R. E. (1974). ‘Introduction to Statistics.’ 2nd edn. (Macmillan: New York.)

Ward, T. M. (1996). Sea snake bycatch of prawn trawlers on the northern Australian continental shelf. Marine and Freshwater Research 47, 631–635.
| Crossref | GoogleScholarGoogle Scholar |

Ward, T. M. (2000). Factors affecting the catch rates and relative abundance of sea snakes in the by-catch of trawlers targeting tiger and endeavour prawns on the northern Australian continental shelf. Marine and Freshwater Research 51, 155–164.
| Crossref | GoogleScholarGoogle Scholar |

Wassenberg, T. J. , Milton, D. A. , and Burridge, C. Y. (2001). Survival rates of sea snakes caught by demersal trawlers in northern and eastern Australia. Biological Conservation 100, 271–280.
| Crossref | GoogleScholarGoogle Scholar |

Wassenberg, T. J. , Salini, J. P. , Heatwole, H. , and Kerr, J. D. (1994). Incidental capture of sea snakes (Hydrophiidae) by prawn trawlers in the Gulf of Carpentaria, Australia. Australian Journal of Marine and Freshwater Research 45, 429–443.
| Crossref | GoogleScholarGoogle Scholar |

Zhou, S. , and Griffiths, S. P. (2008). Sustainability Assessment for Fishing Effects (SAFE): a new quantitative ecological risk assessment method and its application to elasmobranch bycatch in an Australian trawl fishery. Fisheries Research 91, 56–68.
| Crossref | GoogleScholarGoogle Scholar |