How empty is the ocean?

For millennia, the human race has been exploiting the oceans' riches without too much concern about their condition at the time or in the future. It is not so long ago that working the seas was almost exclusively the business of seafarers and fishermen. With the advent of improved technology, global population growth and the boom in consumer demand, the 20th century saw an accelerating extraction of mineral and living resources from the oceans. This has been accompanied by modern farming, industrial and urban settlements along the ocean's coastlines.

Willy-nilly, the fishing industry found itself sharing the sea with other stakeholders: longshore developers and the resulting population, under-sea oil prospectors and the whole oil-extracting industry, with military navies with their powerful technologies that affect the ecosystem in various way and of course multitudes of recreational fishermen. Nor must we forget the public at large, represented by various authorities and, more recently, by various environmental groups and lobbies.

The developing 'industrialisation' of the sea has been accompanied by increased pollution from both coastal and marine sources. Somewhere in there we must also take into account natural and perhaps man-made climatic variations.

The empty ocean

Some of the world oceans' ecosystems began to show signs of distress, one of them being depletion of various marine populations.

A recent offering, which attempts to analyse the state of affairs, comes from the pen of Richard Ellis of the New York Museum of Natural History, an experienced author of 14 other books, many of which are about marine life and the environment. Called 'The Empty Ocean'*, he looks at the depletion of mainly commercial fish, marine birds and mammals. The book's alarmist title is a misnomer, for although its narrative is about an array of threatened marine animals, Ellis' ocean is far from being 'empty'. Evidently, alarmist titles sell better nowadays.

Unfortunately, as many authors on the environment are wont to do, Ellis, in his second chapter, devoted to 'Decline of the fisheries', only examines those species and fisheries that have been subject to depletion or even stock collapse and only the negative effects of fishing operations on the environment. While it is fairly truthful, well-referenced and informative the book almost totally ignores upstream, coastal and marine pollution and the role of climatic variations in the upward and downward fluctuations of fish populations. Such biased focusing on fishing, as virtually the only factor affecting the health of the marine environment, may be politically and commercially functional, but it creates a distorted public perception of what is really happening in the ocean.

In 15 chapters he deals with fisheries, sea turtles, marine birds, all sorts of seals, sea lions and elephants, whales, dolphins and porpoises, coral reefs and biological invaders. For those who have not examined this area 'The empty Ocean' does brings home the plight of many endangered, depleted and already exterminated marine species. Of particular historical interest is the description of the abolition of the 'tuna-on-dolphin' purse seine fishery off California.

The story of the massive collapse, following the invasion of comb jelly, and recovery of the Black Sea's ecosystem, is of a major ecological interest, for it involves pollution, invasion by an exotic species, destruction of fish stocks, collapse by implosion of the enormous biomass of the invading predator and, finally, the recovery of the ecosystem.

Oil and gas

A much more specific aspect of industrialisation of the sea comes in a roundup conference report on oil and gas impacts in the Gulf of Mexico in 'Fisheries, Reefs and Offshore Development'. The title is perhaps somewhat aspirational since this book deals principally with the state of marine environment in relation to fishery (mainly of red snapper) and oil and gas prospecting and extracting industry in the Gulf of Mexico (GoM). Since 1947, in the northern GOM, offshore oilrigs have influenced marine organisms and their exploitation. There are now thousands of installations worldwide so the implications for fisheries are an issue worth examining.

This brings together 28 authors contributing to 14 chapters and hence represents decades of research on the impact of oilrigs on the abundance and distribution of fish. The debate about the effect of fixed oilrigs on the environment has various elements. There is the role of platforms as artificial reefs which enhance life in their vicinity. On the other hand there are spills during the production phase, pollution oozing from abandoned rigs and the effects of these elements on the marine habitat. The jury is still out on the 'rigs-to-reefs' concept, by which redundant installations are sunk at sea to serve as artificial reefs. While the North Sea is examined in this context in chapter 1, all other chapters focus on the Gulf of Mexico which may have the world's largest and unique assemblage of such artificial reefs.

Artificial desert reefs?

This author searched for some concrete conclusions relevant to fishery management but only found a few in a paper on site fidelity and dispersion of red snapper associated with artificial reefs. Written by W.F.Patterson and J.H.Cowan of Alabama, USA. Their results, obtained by tagging some 3,000 red snappers, do not seem to support the view that artificial reefs have increased red snapper production.

Their artificial reefs seem to attract mainly fishes with low and only opportunistic dependency on the reefs, and hence their site fidelity is also low. The authors call for incorporation of site fidelity and dispersion rates in the models used by proponents of marine protected areas when assessing their efficacy.

Alas, one must conclude the bulk of the conference book report has little to do with

'Fisheries and Offshore Development'.

*Island Press/Shearwater Books, Wash. D.C., www.islandpress.org, 2003, 367p.

**Edited by David Stanley and Ann Scarborough-Bull and published in 2003 by the American Fisheries Society (afspubs@pbd.com), it represents proceedings of the 2000 workshop "Gulf of Mexico Fish and Fisheries: Bringing Together New and Recent Research".