Reducing interactions with marine mammals in the Gulf of Carpentaria Gillnet Fishery using acoustic alarms and pingers

Photo: Dennis Ballam, OWA’s Queensland SeaNet Officer with the “pinger” on the left and the Marine Mammal Early Warning System device on the right.

The Gulf of Carpentaria Commercial Fishermen’s Association (GoCCFA) is maintaining it’s proactive approach to utilise all available procedures to prevent negative interactions with marine mammals. Accordingly they are engaged in a Northern Gulf NRM sponsored collaborative project with OWA’s Queensland SeaNet officer Denis Ballam, the Qld Department of Primary Industries and Fisheries (DPI&F), ECOfish and James Cook University Electrical Engineering to develop an integrated package of techniques for industry operators to meet biodiversity targets under the EPBC Act.

The project follows on from a previous NHT funded project on pingers in Gulf fisheries that incorporated the observed reactions of wild animals to acoustic alarms in Queensland and captive animals in Indonesia.  Industry volunteers in the Gulf use the devices to reduce entanglements of dolphins and dugongs when they are detected at fishing grounds.  This project intends to improve the fishing industries’ capability to do this.

Low frequency acoustic alarms attached to nets are designed to warn whales and dugong of the presence of the nets.  High frequency acoustic pingers provide the same function while focussing more on the high frequency hearing capability of dolphins.  Industry will be provided with a combined acoustic alarm and pinger designed and built in a collaborative effort with FNQ industries to help minimise entanglements of marine mammals.

Pingers to reduce dolphin entanglement are now obligatory in European fisheries that use gillnets.  The UK RSPCA assists by showing fishermen how to deploy them. An internationally accepted pinger output has been selected and incorporated into an electronics package in the pingers for the GoCCFA. OWA’s SeaNet Officer will be showing the fishers how to deploy them in the Gulf gillnet fishery.

A recent publication in the world’s foremost acoustical science journal, the Journal of the Acoustical Society of America, demonstrated how Japanese researchers in Thailand monitored, and tracked dugong using acoustical methods.  The researchers warned of the errors involved using conventional daylight only visual techniques conducted at a time when fishing does not occur and dugong behaviour is totally unlike their night time behaviour.

The research described the vocalisations of dugong during the day as being negligible, escalating rapidly during the hours of darkness when the main sense available to them would be sound reception. The time of sound production coinciding with normal Queensland gillnet fishing times. 

The frequency of the dugongs’ sound production in Thailand, and other areas where it has been described, provided further confirmation that healthy animals can hear the acoustic alarms developed for this study.

The project has drawn from the collective experience of the fishing industry with dugong clearly demonstrating that the species moves at night, as confirmed by the Japanese work. Moving animals vocalise far more at night than they do during the day and as such, are far more responsive to noise, namely their own calls or noises from anchored vessels or gillnets with acoustic alarms in their swimming path.

To assist fishing operations to avoid entanglements with marine mammals, vessels will be provided with a commercial quality hydrophone intended to detect dolphin and dugong sounds.  Gillnet operators in attendance with their nets will be able to detect the presence of marine mammals in the vicinity of their nets during the hours of darkness and make fishing decisions to avoid entanglement. 

Larger vessels will be equipped with a project designed Marine Mammal Early Warning System based on multiple hydrophones utilising on-board computers and localisation systems, developed in association with a recent Fisheries Research and Development Corporation study on toothed whales in the Coral Sea.

Construction of the acoustic devices is underway at the Northern Fisheries Centre in Cairns and roll out to the GoCCFA gillnet fishers should begin in October 2006.