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A Guide to Science, Design, and Use
By Jack Sobel, Craig Dahlgren
ISLAND PRESSCopyright © 2004 The Ocean Conservancy
All rights reserved.
Our Oceans in Trouble
People who know the sea well know something is wrong. Children visit the sea and listen in disbelief to stories about the good old days. Then they grow up, have their own kids, tell their own stories, and understand something's missing, that their kids are being deprived of something that once brought them great pleasure. Sophisticated media coverage also increasingly highlights and documents these changes for us, but with each generation, the clock is reset and we forget what came before, minimizing the perceived change. Yet, one need only look at a map of the coast or walk around a coastal community to find names of places like Sheepshead Bay, where no one's caught a sheepshead in a generation; Halibut Cove, where no one may ever catch a halibut again; Jewfish Creek, where no one remembers the last jewfish; or Salmon Run, where the last run occurred before anyone alive today was born. In a very real way, we are losing our natural marine heritage and our biodiversity, and it matters.
Over a century ago, scientists first noted rapid changes occurring along the east coast of North America. According to the U.S. Commission of Fish and Fisheries, halibut from coastal New England had been nearly extirpated by 1878 (see the following quote). Dwindling cod stocks triggered a decline in landings from their historic peak in 1887, followed by other targeted groundfish species in the ensuing decades (Fig. 1.1; NMFS 1990). Natural oyster reef habitat had been virtually eliminated throughout the Chesapeake Bay and northeastern United States (Brooks 1996). Similar changes had already been observed in Europe. The following summary vividly encapsulates the changing sea state at that time.
Wherever ... man plants his foot and the "civilization" is begun, the inhabitants of the air, the land, and the water, begin to disappear.... The fish, overwhelmingly numerous at first, ... feel the fatal influence in even less time than the [terrestrial] classes.... The halibut, one of the best of our fishes, was so common along the New England coast as not to be considered worthy of capture.... It is only within [the last] few years that our people have come to learn their excellence and value, but they have already disappeared almost entirely from the inshores of New England, and have become exterminated in nearly all waters of less than five hundred feet in depth. (United States Commission of Fish and Fisheries 1880, p. xlv)
But this report represented a minority view. A century ago, the prevailing scientific and public views of the ocean's living resources remained closer to this Thomas Huxley (1883) vision presented in his inaugural address to the 1883 Fisheries Exhibition in London: "Probably all the great sea fisheries are inexhaustible." Despite this oft-quoted proclamation, Huxley did acknowledge in his address that some fisheries, even some sea fisheries, were in fact exhaustible. The scientist within him could not ignore the empirical evidence that some of the fisheries he researched, notably the European oyster and certain salmon fisheries, had already been largely depleted.
But this did not change the conventional wisdom, that (1) little threat of endangerment, extirpation, or extinction existed for most marine species or ecosystems; (2) the well-documented vulnerability of a few notable exceptions, including some marine mammals, sea turtles, sea birds, estuaries, and coral reefs, extended to little else, especially most marine fish and invertebrates; and (3) the main targets of the world's great fisheries, which still retained a cloak of inexorable, and even magical, invincibility, were somehow immune to such outcomes.
For most of the past century, this dogmatic view remained dominant. Although in recent decades, minority voices within and outside the scientific community started to question it, the assumption of many was that managers could protect any individual species through tools like catch limits, gear restrictions, and other traditional tools. Without compelling evidence to the contrary, sustainable fisheries management was seen as achievable and just around the corner, using these tools, though perhaps needing better information and more political will.
To be fair, for much of human history, the oceans did seem relatively resistant and resilient to our actions, capable of both maintaining themselves and supplying a continued stream of fish, shellfish, and other valuable commodities. Areas undiscovered by fishermen or too far from port, too deep, or too difficult to fish for other reasons, served as "natural refuges" from fishing and protected intact marine communities. This helped maintain healthy marine ecosystems, protect biodiversity, and support fisheries. However, new and improved gear and technology, increased capacity, shifting targets, and rising market prices have enabled exploitation of both previously unfished natural reserves and formerly nontargeted species. As a result, these natural reserves have largely disappeared; their ability to help protect biodiversity, maintain healthy ecosystems, and replenish other fished areas is greatly reduced; and both the magnitude and geographic scope of fishing impacts have been greatly increased.
Slowly, the tide of scientific and public opinion is turning. Within the past ten years it has accelerated, approaching bore velocity, and the prevailing views on this may now be amid a phase shift. A few years ago, we still lacked a strong article in a prestigious journal or a consensus statement from a respected independent group of prominent scientists on the true scope of marine endangerment. We now have several (e.g., Jackson et al. 2001).
RISING TIDE OF MARINE ENDANGERMENT
While some questions related to the degree of extinction risk for marine fish and invertebrates remain lively topics, the same questions for marine mammals, sea birds, and sea turtles should have been resolved long ago. Human exploitation including fishing and other impacts clearly puts these animals at risk for extinction; the empirical evidence for their susceptibility is really beyond serious debate. Though less well known than their terrestrial counterparts, the rapid disappearance of Steller's sea cow (Hydrodamalis gigas), the Caribbean monk seal (Monachus tropicalis), and the great auk (Pinguinis impennis) (Roberts and Hawkins 1999) following brief contact with mobile human hunters in very different and geographically distinct ecosystems provides three of the most striking illustrations of their susceptibility. Steller's sea cow disappeared within just a few decades of contact with North Pacific whalers once seagoing whaling boats and technology arrived there. The Caribbean monk seal and great auk took slightly longer to succumb, but were still gone within a century or so of similar contact. The sea mink (Mustela macrodon) similarly disappeared from North Atlantic coastal waters by the close of the nineteenth century (COSEWIC 2002).
All of the great whales and sea turtles have teetered on the brink of extinction, but miraculously, none have thus far toppled from the precipice. Some have withstood extirpations, to which we lost the Atlantic gray whale (Eschrichtius robustus) (Mead and Mitchell 1984), along with the Atlantic walrus (Odobenus rosmarus rosmarus) (COSEWIC 2002). Others have seen dramatic declines such as those described for Caribbean sea turtles (Jackson 1997). All remain endangered or threatened and none have yet escaped extinction. Most have been given a respite through a complete or partial cessation of intentional, directed killing, but not all. Even some of those now fully protected from such directed take remain highly endangered. The northern right whale (Balaena g. glacialis) herd has been reduced to several hundred and continues to face threats from vessel strikes, entanglement in fishing gear, and minimum viable population size. Steller's sea lion (Eumetopias jubatus) likewise is still facing a suite of interlocking threats in the North Pacific.
Documented marine fish and invertebrate extinctions resulting from human impact are relatively few and less dramatic. Until recently, little attention has been paid to them. They remain more likely to go unnoticed, and threats to them are often more difficult to prove. However, there is a rapidly increasing suite of such organisms approaching the brink and a number that may already be extinct (Fig. 1.4). These include a diverse array of finfish, shellfish, and other invertebrates with a variety of life histories and distributions from around the globe. Perhaps most remarkable, the Canadian government recently listed two populations of the Atlantic cod, once seemingly ubiquitous across the North Atlantic, as endangered and threatened. Within the last three decades, the Newfoundland and Labrador cod population declined roughly 97 percent and the species virtually disappeared from some offshore areas (COSEWIC 2003).
The striking case of California's white abalone, Haliotis sorenseni, provides a clear and present example of the extinction risk posed to at least some marine species from targeted fisheries. This abalone occupied a relatively narrow depth range and small geographic range, but was fairly abundant in waters between 25 and 65 meters deep around California's Channel Islands until the early 1970s. At this time, a short-lived commercial fishery targeted this species, employing a handful of fishers for less than a decade. Within the span of just a few years, the fishery itself was extinct and the species was on the brink (Fig. 1.2). Commercial landings peaked at 65 tons in 1972, but plummeted to 0.15 tons in just four years. In the early 1990s, intensive searches in known habitats that once harbored densities of up to 10,000 abalone/hectare yielded only a few dozen. Abalone require minimum densities for successful fertilization and recruitment. There is no evidence of significant recruitment or landings in the last several decades. The white abalone appears to be approaching extinction, even though the brief, but intense, fishery that caused its initial collapse ended decades ago. Efforts are now being made to concentrate some of the few remaining adults in an attempt to facilitate successful reproduction, but it may be too late (Davis et al. 1996; Tegner et al. 1996).
The Nassau grouper (Epinephelus striatus), a large, long-lived species, formerly common throughout the Caribbean, provides another striking example of vulnerability to exploitation and associated extinction risk. Once an important apex predator, the dominant grouper on many Wider Caribbean coral reefs, and a species of considerable commercial importance, it is today absent or rare across much of the region. Where it still exists, it is much smaller and less numerous than it previously was. Despite its relatively broad distribution and once large numbers, it is exceptionally vulnerable to fishing. The Nassau grouper fears little, aggressively attacks baits, approaches divers, and eagerly enters traps. But the mating habits of the Nassau grouper may ultimately be its downfall. It is a protogynous (female first), hermaphroditic (sex-changing), group spawner that aggregates in large numbers to spawn at specific sites for a short predictable time each year. These reproductive habits are a double whammy. First, the targeting of larger, older fish by fishermen means that the big males with greatest reproductive capacity are largely removed from the population. Nassau grouper are also very vulnerable to fishing while aggregating at their spawning sites, and fishers frequently target known spawning sites. Such aggregations once numbered in the tens of thousands of fish. At least a third of these once huge aggregations no longer exist. Despite closures to both spawning sites and targeted fishing, some aggregations and populations have not shown signs of recovery, possibly because measures came too late or because of continued bycatch. The Nassau grouper is currently listed as endangered on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List and a candidate species for the U.S. Endangered Species Act (ESA) (Coleman et al. 2000; Sadovy and Eklund 1999).
Australia's unusual spotted handfish (Brachionichthys hirsutus) provides a third striking example of a marine fish recently brought perilously close to and now teetering on the brink of extinction. So named because of its somewhat peculiar habit of walking on its fins rather than swimming, this fascinating species was one of the first Australian fish discovered and could be among the world's first lost due to human activity. The handfish is restricted to a narrow range within a single Australian estuary and is capable of only limited movement. It lays a small number of benthic eggs that remain on the bottom and have limited dispersal capacity. The primary threat to its continued existence is predation on its benthic eggs by the exotic northern Pacific sea star. This alien sea star, likely introduced via ship ballast water, is not a natural predator of handfish eggs. Trawling, dredging, pollution, modification of freshwater flow, and other activities that could disturb its estuarine habitat are also potential threats, as is any targeted collecting that may result from its rarity or value (Pogonoski et al. 2002).
Despite the increased recognition of extinction risk for fish, a proliferation of petitions to list fish under the U.S. ESA, and a growing list of additions to its candidate species list, until recently there remained no exclusively marine domestic fish listed on it. Prior to 2003, the only marine fish listed under the U.S. ESA were anadromous species that spawn in fresh or estuarine water, with the possible exception of the totoaba (Totoaba macdonaldi), a species that spawns only in the northern Sea of Cortez near the mouth of the Colorado River in Mexico. However, the eventual listing of a domestic truly marine fish under the U.S. ESA was only a question of when and which species.
On April 1, 2003, the listing of the smalltooth sawfish (Pristis pectinata) as endangered under the U.S. ESA answered these questions. This majestic and charismatic species may grow to 25 feet (7 meters) in length and bears a large sawlike snout responsible for its name (Fig. 1.3). Once common in the United States from North Carolina to Texas, dramatic reductions in range and numbers now largely restrict it to the extreme southern tip of the Florida peninsula and a population size less than 1 percent of its historical abundance. The current distribution is focused around Everglades National Park and Florida Bay, where it was once abundant enough to be the target of a recreational bow and arrow fishery. Commercial fisheries landings and incidental take were primarily responsible for reducing this species and bringing it to the brink of extinction, but typical of many endangered species, a multitude of factors, including habitat loss, pollution, modified water flow, and continued bycatch now conspire to keep it there or finish it off (NMFS 2003). Perhaps it was foolish to wait so long.
Prior to the sawfish listing, the totoaba was likely the most marine fish listed under the U.S. ESA. It provides another excellent and interesting example of how human activities, often acting in concert, can rapidly endanger a marine fish. The largest member of the drum or croaker family (Scianidae), the totoaba was endemic to and abundant in the Sea of Cortez (Baja California), where it aggregated to spawn in the lower reaches of the Colorado River. The common names of this family stem from sounds produced by vibrating their swim bladders. Mexican fishers initially targeted this species in the 1920s, primarily for their swim bladders and the high price they fetched in Asian seafood markets. Nonetheless, the catch peaked by 1942 at close to 5 million pounds and declined precipitously thereafter. Although the directed catch was clearly responsible for the initial decline of this species, damming of the Colorado River and bycatch from an intensive shrimp fishery subsequently furthered its decline and continue to endanger it (Norse 1993).
Excerpted from Marine Reserves by Jack Sobel, Craig Dahlgren. Copyright © 2004 The Ocean Conservancy. Excerpted by permission of ISLAND PRESS.
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