Management of offal discharge

Seabirds
 
This description relies upon Birdlife International (2014) and ACAP (2021).
 
Birds are attracted to fishing vessels to feed on processing waste and discarded fish. Removing this source of food can greatly reduce the number of birds associating with fishing vessels. Until recently, most longliners were designed in such a way that offal discharge occurred adjacent to the hauling hatch. This resulted in large numbers of birds feeding amongst hooks that were being hauled aboard. Now, a minimum requirement in many fisheries is to position the scupper, through which waste is discharged, on the port side of the vessel (opposite to the hauling hatch). This helps to divert the birds’ attention away from the area where hooks return to the surface. However, strategic discharge during line setting can increase interactions. Where practical, the discharge of offal should be eliminated or restricted to periods when not setting or hauling, though offal retention and/or incineration may be impractical on small vessels.
 

In summary, ACAP (2021) describe strategic offal discharge as good practice, a supplementary rather than a primary mitigation measure, and recommend that:

  • offal and discards should not be discharged during line setting;
  • during line hauling, offal and used baits should preferably be retained or discharged on the opposite side of the vessel from that on which the line is hauled; and
  • all hooks should be removed and retained on board before discards are discharged from the vessel.

 

Sharks

With regard to sharks, offal management includes the practices of chumming during setting or discarding of offal during hauling. However, little is known of the impact upon shark catch rates of these practices.

A recent (2007, 2008) study of 12 pelagic longline fisheries from eight countries found very few fishers who believed that refraining from chumming during the set and refraining from discarding offal and spent bait during the haul would affect shark interactions. It was found that chumming during setting was not a common practice and that offal and spent bait were typically discarded during hauling operations. Many of those interviewed explained that it would be impractical to retain spent bait and offal to discard at the end of hauling due to limited space on the vessels.

Effect on Other Bycatch Species

None.

Compliance
Seabirds
Requires offal discharge practices and events to be monitored by fisheries observers or video surveillance. However, strategic offal management can be inconvenient during operational processes and generally has low compliance. Even with strict regulations and 100% observer coverage to monitor these measures, 100% compliance is not easy to achieve. Greater awareness is needed among fishermen of the long-term implications for birds that are hooked on hauling, as even those released alive face reduced likelihood of long-term survival.
 
Further Research

Further information needed on opportunities and constraints for the application of offal management in pelagic fisheries (short and long term).

References
  1. ACAP. 2011. AC5 Annex 7 - Summary advice statement for reducing impact of pelagic longline gear on seabirds. Fourth Meeting of the Seabird Working Group, Guayaquil, Ecuador. SBWG-4 Doc 12.
  2. Birdlife International (2014) Bycatch Mitigation Fact-Sheet 12. Demersal and Pelagic Longline: Haul mitigation. English, Japanese, Korean, Portuguese, Simplified & Traditional Chinese.
  3. Gilman, E., Clarke, S., Brothers, N., Alfaro-Shigueto, J., Mandelman, J., Mangel, J.,  Petersen, S., Piovano, S., Thomson, N.,  Dalzell, P.,  Donoso, M., Goren, M. and Werner, T. 2007. Shark depredation and unwanted bycatch in pelagic longline fisheries: Industry practices and attitudes, and shark avoidance strategies. Western Pacific Regional Fishery Management Council, Honolulu, USA.
  4. Gilman, E., Clarke, S., Brothers, N., Alfaro-Shigueto, J., Mandelman, J., Mangel, J.,  Petersen, S., Piovano, S., Thomson, N.,  Dalzell, P.,  Donoso, M., Goren, M. and Werner, T. 2008. Shark interactions in pelagic longline fisheries. Marine Policy 32(1): 1-18.
  5. ACAP. 2021. ACAP Review of mitigation measures and Best Practice Advice for Reducing the Impact of Pelagic Longline Fisheries on Seabirds. In: ACAP - Twelth Meeting of the Advisory Committee. Online