Deep-sea sharks: Poorly known, poorly managed
Author: Allison Perry
Date: May 7, 2014
The intriguing species that live in the deep-sea, hundreds of metres below the ocean’s surface, are some of the least suitable fish in the world for supporting commercial fisheries. Physiologically, they have adapted to life in a cold, dark environment where resources are patchy and in scarce supply. As a result, biological processes happen on a much slower timescale for many deep-sea fish than for species that live in shallow waters; they grow slowly, they begin to reproduce at a late age, and can live for many years. For example, the black cardinalfish (Epigonus telescopus), a species found on soft bottoms in the depths of the Atlantic, Indian, and Pacific Oceans, can reach 104 years of age.
Because they live at such great depths, it is much more difficult and expensive to observe and study deep-sea species than those that live in shallower waters. As a result, our knowledge about the majority of species in deep waters is very limited. Many are known only from incidental captures, among the many species that are taken as by-catch and discarded (dead) from commercial fishing operations. This lack of knowledge about their populations, combined with weak EU management measures in place since 2002, has led to a dire but unsurprising situation: out of roughly 100 species captured in deep-sea fisheries in the North-East Atlantic, only three species have one or more stocks that seem to be in good condition.
The most vulnerable and poorly known species include the deep-sea sharks. These fascinating animals are typically dark-skinned creatures with huge, iridescent green eyes that allow them to capture as much light as possible in dark waters. Among deep-sea fish, the sharks are particularly long-lived and slow to recover from overfishing. Their populations increase at rates that are among the slowest known for any fishes, with species such as the birdbeak dogfish (Deania calcea) taking half a century to double its population size under natural conditions without fishing pressure.
In the EU, the status of deep-sea sharks is an issue of serious concern. Some species have been heavily overfished as a result of fisheries that have targeted them for their large livers, rich in oils that are used for cosmetics, dietary supplements, and even vaccines. As a result, 17 species of deep-sea sharks have been prohibited for directed fisheries, retention, or landing since 2012, because they have already been depleted or because there are concerns about their future depletion.
This measure was a positive and necessary step, but it is not sufficient. It helps to prevent further directed fisheries for these vulnerable species, but it does nothing to prevent them from being accidentally captured – and killed – in deep-sea fisheries. Nor does it include all of the deep-sea sharks that are caught in the North-East Atlantic.
One striking example concerns gulper sharks (Centrophorus spp.), which have been heavily targeted for the trade in shark liver oil, causing significant declines in some species. Until recently, EU management measures have only applied to two species (C. granulosus and C. squamosus) while at least two others (C. lusitanicus and C. niaukang) were left unmanaged. In 2013, the International Council for the Exploration of the Sea (ICES) recommended that all gulper sharks should be managed, because of their high vulnerability to overexploitation and the fact that different species of gulpers are very similar in appearance, which creates potential loopholes for enforcement if management measures only apply to some, but not all, species. As a result of the ICES advice, all gulper sharks have now been prohibited for retention or landing until the end of 2014. However, the current (2002) regulation on deep-sea fisheries in the North-East Atlantic still only covers two species. It is important that all of the gulper sharks also be included under a revised deep-sea regulation, in order to guarantee that all relevant management measures are applied to this vulnerable group of sharks.
This example is just one of many that highlights why the EU regulation on deep-sea fisheries in the North-East Atlantic is in need of a serious overhaul, and why we ask that the new regulation, which is currently being discussed in the EU Council of Ministers, apply equally to all deep-sea species.
Sign our joint NGO petition calling on the Spain to lead and support strong EU measures for deep-sea fisheries management – to ensure sustainable deep-sea fisheries and protect vulnerable deep-sea habitats such as coldwater corals and sponges.