Seabird-warp interactions

Interactions between seabirds and trawl gear have been recorded as part of the SADSTIA observer program since June 2013. Data were collected during daylight hours by observers who counted the number of birds that interacted (touched or collided) with the warps during a 35 minute period.

Collisions (or other interactions) with the warps were considered as high, medium or low impact, with a possible outcome of dead, possibly dead, injured or uninjured. For example, a high impact collision could result in the bird being injured or if the bird was subsequently dragged under water for longer than ca. 30 seconds it was assumed dead or possibly dead. Medium impact collisions that resulted in a deviation in a bird’s flight path could be assumed to result in injury or being uninjured. Low impact collisions occur when the bird touches the warp and is uninjured. Birds that were brought (hauled) onboard at any stage of the trip were also recorded with respect to where they were caught in the net (wings, belly or codend) and the outcome (dead, injured or uninjured). Dead birds were labelled, bagged and frozen for research purposes to be undertaken at BirdLife South Africa.

Observations took place in the vicinity of the warps where most seabird activity occurred. This usually occurred near the warp closest to on where the majority of offal was discarded. In addition to bird observations, the following data were collected; position, sea surface temperature, cloud cover, depth and wind speed and direction. The amount and a description of offal/discards were also recorded as well as tori line information such as their presence/absence, when they were deployed and the percentage of the warps covered by the tori lines.

To date a total of 89 hours has been spent observing seabird warp interactions during 188 trawls since observations started in June 2013. The large majority of interactions recorded (99%) were LOW impacts and the birds were UNINJURED. On four occasions the impact was rated HIGH: in these instances the bird survived but was considered INJURED. There were no observations of any Endangered, Threatened and Protected (ETP) species, such as the black-browed albatross (Thalassarche melanophris) and the shy albatross (Thalassarche cauta), being involved in interactions during this period.

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