1.6.2 Marine

• Globally, commercial fisheries have had significant impacts on seabird populations. Long-line, gillnet (or setnet) and trawl fisheries have been notorious for pelagic seabird by-catch and overexploitation of fish stocks. Seabirds are opportunistic foragers and are often drawn to discards and offal from working fishing vessels. Reporting from fisheries shows that most seabirds caught within Pacific island countries EEZs are those that breed elsewhere, however bycatch rates of seabirds breeding within the region are largely unknown.
  • Beyond by-catch, fisheries may impact seabird populations by reducing available prey species, particularly at crucial periods of the breeding cycle where parents are foraging for both themselves and a dependent chick (or chicks). Loss of predatory fish removes their natural action of chasing their favoured prey to the surface and thus having these smaller fish available for seabirds.15 In addition, the large-scale removal of both prey and non-prey species may compound the direct effects that impact seabird populations, where indirect effects result in greater declines.
• Pollution:
  • Marine plastic pollution is a pervasive global issue. Seabirds can ingest plastics mistaken for prey at sea and fed to chicks. Plastics cause internal blockages or perforations or result in gradual starvation by filling the digestive tract in place of food, preventing birds from fledging.
  • Birds can also become entangled in marine debris including abandoned, lost and discarded fishing gear (ALDFG).
  • Oil spills can be caused by vessels wrecking on shorelines or reefs, fouling and killing seabirds foraging in the slicks. There is also an unquantified risk of oil pollution from sunken World War II wrecks in the Pacific, such as at Truk Lagoon. Oil at sea is a threat to seabirds because it forms a thin layer on the water surface where many seabirds spend most of their time. Likewise, other marine life, including prey species for seabirds can be affected. Oil discharges from vessels can be caused by malfunctioning equipment, negligence, or wilful illegal actions including tank washings, dirty ballast, and bilge pumping.
• Deep-sea mining may irreparably harm ocean ecosystems before we have a chance to understand the extent of its impacts, including to seabirds.
• Climate change:
  • Greater storm intensity and frequency will increase the turbidity of coastal waters, which may impact foraging success in visual foragers such as boobies, noddies and terns. It can also have severe impacts on the breeding colonies themselves as noted above.
  • Certain prey species may decline or shift in their distribution, confounding their pulse timing relative to seabird breeding cycles. This could have serious knock-on effects for reproductive success and even make large areas of current breeding distribution no longer suitable for seabirds in the future (particularly species with short foraging ranges). It is possible that other prey species may take their place, potentially ameliorating the loss of one resource with another. The implications of this will depend on whether the replacement is a suitable replacement (similar energy content by foraging effort) to the original prey source, and how this may impact reproductive success and long-term survival. For seabirds that disperse following breeding reduction in available food resources in nonbreeding areas could lead to reduction in breeding fitness.