Vessels maiming sea species
SHEREE BEGA
WHALES, dolphins, sharks, sea otters, seals, dugongs, penguins and sea turtles are among the 75 different marine species affected by ship collisions.
And it’s not just large commercial vessels that are responsible, said Claire Patterson-abrolat of the Endangered Wildlife Trust, but small recreational vessels too.
Injury to the animals can be “pretty horrific”, she said, ranging from minor injuries to deep lacerations, fractures, haemorrhaging, amputated body parts such as fins or tails or even death.
Injuries may also lead to reduced fitness which in turn lowers reproduction rates.
Patterson-abrolat’s research findings – together with researchers Dr Renee Schoeman and Dr Stephanie Plön, both of the Nelson Mandela University – A Global Review of Vessel Collisions With Marine Animals, were published in a review in Frontiers of Marine Science.
Their research showed that collisions between marine animals and ships occur far more regularly than previously thought.
Long-lived species, which take longer to reach sexual maturity and give birth to just one or two young at a time, are the most affected,
Concern about the effects of maritime vessel collisions with marine animals is increasing worldwide, the researchers say, with the finding that “collisions with marine life may comprise a much larger problem than initially thought”.
“However, for most smaller species, we know little about the extent of collision incidences. Collision reports for smaller marine species are generally scarce, likely due, at least in part, to a reporting bias rather than collisions with smaller species being less frequent.
“We know that collisions between large vessels and whales may not be reported because vessel crew are not aware of the collision. In addition, fatal collisions with most cetaceans, whale sharks and sea turtles likely go unnoticed because carcasses sink quickly.”
Even if carcasses float, they may be consumed by scavengers or decompose before they reach the shore.
Vessels too may incur damage such as cracked hulls or broken propellers.
“In a few cases, the ship’s crew can also be injured, with extreme cases resulting in being knocked overboard and loss of life,” said Patterson-abrolat.
Temporary rerouting of ships during breeding seasons could reduce the risk of collisions, but this is often directed only for whales; many other vulnerable species often receive little or no attention.
Establishing communication channels with reporting and early warning systems could give both the ships and the animals more time to take avoidance procedures.
Having a trained observer on board can also increase the detection of an animal in the water allowing the ship to alter course or warn the animal of its presence.
A range of deterrent devices has been found effective on species such as the North Atlantic right whale but were not effective on gray whales.
A manatee alert device has proved successful in alerting that species. Propeller guards have also been found to be successful for species such as loggerhead turtles.
A centralised database of all collisions noted in the oceans should be developed “to allow the identification of potential hotspot areas”.
Research should be conducted to determine whether injured species have a reduced breeding success rate and how this impacts on populations.
Enforcement should be stepped up where necessary to ensure adherence to speed reduction zones, and education and awareness materials should be made available to ship crews, and recreational skippers, the researchers say.