Emptying Oceans

The status of marine vertebrates can be considered the unsung conservation crisis of our time with little be advertised on all media types about population declines or highlighting vulnerability. Such publicised conservation efforts are reserved for other terrestrial animals such Amur leopards, Giant Pandas or global ecosystems such as the amazon rainforest. In part this can be contributed to our empathy towards are fellow terrestrial organisms but ultimately it come down to what we can actually see, and in this case what is happening below the surface largely goes unnoticed. Some of this lack of public knowledge could be associated with the save the whale conservation actions of the mid 70's where there was public outcry over Japanese and worldwide whaling activities, though it seems that the public has considered this problem “Resolved” and cetaceans no longer under threat due to strict controls on whaling or the lack of participating countries. Or the belief the ocean inhabitants are capable of buffering against our harvesting techniques. This is not the case with the large percentages of marine vertebrates classed within higher levels of vulnerability according to IUCN, or even larger percentages of species classed as data deficient due to the inability to monitor them or the lack of funding opportunities due their lack of commercial value. 

Referring back to status of marine vertebrates, marine mammals in particular it has been estimated that ¼ of all marine mammals are classed as vulnerable with an even greater number classed as data deficient 35% to be exact. This severity of vulnerability is large associated with our negative impacts upon the oceans such as increased nautical activities such as shipping and large unknown effects of sonar, but the biggest threat of all is that of fisheries bycatch. An example of species decline ads a result of past human exploitation is that of the Northern Right whale, who's populations are believed to be as fewer than 300 individuals and was classed as nearly reproductively extinct in the wild in 2008 IUCN Red List publication (Fujiwara & Caswell,2001). In contrast the Amur leopard population is said to be just a handful of individuals though this receives global funding and coverage? Following that of marine mammals which have greatest source of empathy than any other, is a taxon containing some of the most important apex predators of the seas, this being sharks and rays elasmobranchs.

Squat-Headed Hammerhead Shark, Endangered,
 Decreasing Population.

The severity and general vulnerability to this species is severe with 47% data deficient with a further 17% threatened and 13% near threatened.  The greatest risk that elasmobranchs are faced with is that of bycatch and over fishing. With large number of sharks annually being harvest for finning to sustain an increasing unsustainable demand in the Far East. Such is illustrated within all 7 sawfish species which are classed as critically endangered as a result of fishing pressures for their desirable saw “noses”.  This vulnerability of sharks is even greater within a regional scale with large pelagic predators nearly extinct from certain parts of the world. One of the most documented shark populations is that of the North West Atlantic, though this in itself is a result of its intense lone line fisheries but has allowed population changes to be estimated since 1986 (Baum et al.,2010). Within the North Western Atlantic species have declined 50% overall within an 8-15 year period, with certain species suffering the brunt. This is illustrated in the hammerhead shark suffering a decline of 89% since 86’, followed by Great white sharks populations decline 79% since 89’ though this is twinned with a greater decline in catch encounter of 80% indicating that the population decline could In fact be significantly more severe .  Though such a study only illustrates a single corner of the globe, its high intensity fisheries could be extrapolated worldwide to similar intensity areas or scaled down to fit less fishery intense areas, allowing global population declines to be estimated.

Hong Kong Grouper, Endangered,
Decreasing population.

Following elasmobranchs is that of bony fish, the second largest taxon on earth second to that of invertebrate life and potentially the most understudies and most commercially exploited. The severity of the exploitation is illustrated with the figure of only 6% out of 15,500 fish species assessed under the IUCN Red List, with the documented decline of 83% on those species that are commercially exploited over the last 2-3 decades (Reynolds et al., 2005). Though the lack of study can be contributed to the difficulty of studying these highly pelagic and migratory species therefore the feasibility is greatly reduced, meaning regional studies have greater influence. Such regional examples include the great mass extinction and exploitation of North Atlantic Cod in Cape Cod, resulting in the collapse of the fisheries and closure of fishing grounds. Subsequent closure was used to allow populations to recover; recent scientific long lining resulted in the capture of just 2 Juvenile cod in 10,000 hooks following a period of 20 years of fishing restrictions. Similarly studies within Flamborough head Cod populations were estimated to sustain number of 3.1million individuals, but forecasted populations only accounted for 121 individuals (Reynolds et al., 2005). Further highlighting the plight of commercially fished species is that of the grouper. Groupers are high desirable and significantly over fished to reach growing Asian demands. Annually 250,000 tons of grouper is fished, across all its life stages due to the demand and the capabilities of captive maturation, reaching demand imposed by the Asian live reef fish food trade. This over exploitation has ultimately results in 12.4% of the 161 grouper specie being classed as threatened and 30% classed as data deficient (IUCN, 2008).

Supporting large numbers of species and a potential keystone in marine ecosystems is that of coral reefs. These are high sensitive species suffering from numerous anthropogenic threats such as ocean acidification, over harvesting or climate change. This has resulted in 27% of 845 skeletal forming corals to be classed as threatened with a further 17% data deficient (IUCN, 2008). In hand with Corals is the decline of worldwide Marine Turtle populations with 6 out of 7 species being classed as threatened with one the Australian endemic Flatback Turtle classed as data deficient. Issues surrounding that of marine turtles are that of whether population should be subjected to global endangered statuses or regional ones, as many populations are isolated and rarely interact with one another. Once such example can be that of the Green and Loggerhead Turtle populations in the Mediterranean.

Amsterdam Albatross, Critically Endangered,
Decreasing Population.

Lastly is the status of Seabirds. Seabirds are one of the most heavily studies groups of all marine vertebrates resulting in only 1% classed as data deficient. Though these species are intensely studied it suffers greatly from a number of threats due to split between aquatic and terrestrial life stages, resulting in 27.5% classed as threatened. Though this number is high certain species are more threatened than other due to differing life history traits, one such example are the captivating albatross species. Albatrosses can be considered the most threatened of all bird species with 89% (19 species) listed at critically endangered with further estimated population declines of 80% over the next 3 generations.







References:

• Baum JK., Myers RA.,Kehler DG., Worm B., Harley SJ., Doherty PA. 2003.Collaspe and Conservation of Shark Popiltaions in the Northwest Atlantic. Science, 299, 389-391.

• Fujiwara M., Caswell H., 2001. Demography of the endangered North Atlantic right whale, Nature, 414,537-540.

• Reynolds JD., Dulvy NK., Goodwin NB. Hutchings JA., 2005. Biology of extinction risk in marine fishes. Proceedings of the Royal Society Biology,272,2337-2344.

• Polidoro, B.A., Livingstone, S.R., Carpenter, K.E., Hutchinson, B., Mast, R.B., Pilcher, N., Sadovy de Mitcheson, Y.and Valenti, S. 2008. Status of the world’s marine species. In: J.-C. Vié, C., Hilton-Taylor, and S.N. Stuart (eds.).The 2008 Review of The IUCN Red List of Threatened Species. IUCN, Gland. Switzerland.