The first image of fish in the context of human endeavor is fish as a source of food and other commodities (e.g. fertilizer). These are dominant, but there are also some negative impacts.
At least 1000 species are implicated as causing illness or death when eaten. The most wide-spread type of poisoning is ciguatera (a particular icthyosarcotoxin - a toxin found in fish flesh and not due to bacterial action). Reports of ciguatera date back to the 7th century AD in China and the 17th century in Europe. Captain James Cook apparently suffered from ciguatera on his 1774 voyage. 400 species are known to cause ciguatera. Many are tropical.
Another common source of poisoning is from fishes not being properly stored. These are generally grouped under scombroid poisoning, but examples are found in at least seven families and 45 species. Tetrodotoxin poisoning is caused by eating the viscera of tetraodontiform fishes, mostly Takifugu (= Fugu), common table fare in Japan. Lampreys and hagfish have been implicated in what is called cyclostome poisoning. Several families of sharks have toxic livers or flesh. Some oily fish cause diarrhea. Hagfishes, lampreys, morays, soapfishes, puffers and their near relatives secrete toxins when disturbed. Many fish are toxic due to the bioaccumulation of pollutants, including mercury, DDT, ketone, PCBs etc. In 1989, 37 states had advisories of some kind.
A number of fish can inflict painful stings that combine mechanical injury with release of venom. The stingrays, as their name suggests are probably the best known. opercular spine.
Electrogenic fishes potentially injurious to people include electric rays, electric eels, and electric catfish. The rostrum billfishes and sawfishes, and needlefish can do considerable damage. The candiru (Vandellia) is reputed to be attracted by urine ... Biting fish include barracuda, sharks, morays, piranhas. Bluefish are reputed to bite the hands and feet of swimmers. There are occasional reports from the Great Lakes of muskellunge biting swimmers.
Most parasites carried by fishes are nematodes, cestodes and trematodes, and usually infect humans as a result of eating raw or insufficiently processed freshwater fish. Some parasites are transmitted to humans from marine fishes. Eating raw minnows has lead to problems of perforation of the intestinal wall by larvae of nematodes of the genus Eustrongyloides. The tape-worm Diphyllobothrium latum, is found in the Great Lakes area.
Fish out of place are becoming increasingly common due to the nature of international human commerce, and sometimes deliberate introductions. Nearly 50 exotics have been introduced into the US and Canada. Some fish have been deliberately introduced for anticipated beneficial uses, e.g. brown trout, carp, grass carp.
Fish in Art
Can you name this piece of art, and the painter?
Gambusia affinis, a poeciliid mosquitofish is used control mosquito larvae. Some cichlids and black carp of Asia eat snails that are intermediate hosts of human parasites. The grass carp is used for weed control species in small isolated lakes and ponds.
Dogfish (Squalus acanthias) and perch (Perca flavescens) are standard dissection examples in labs. Many others are used in bioassays and physiological experiments. The zebra danio is proving an important species for genetic engineering studies.
Humans not only exploit fish, but are directly competing with fish for water, space, and food. The future of humans is closely linked to that of the rest of the globe’s biota, including fish.
Freshwaters are islands and ribbon of water surrounded by a sea of humans! Extinction of endemic species is becoming increasingly common and tolerant, aggressive species are invading the degraded ecosystems. Streams and rivers are the ultimate recipients of the by-products of human activity from sewage to sediment.
The majority of recognized endangered species are FW. Endangered species are most prevalent in regions with one or more of the following characteristics: highly developed economies, small isolated bodies of water, high endemism, arid or Mediterranean climate, big rivers, and big lakes. In the US, 40 species of fishes (in about 1200) are extinct, and 364 need protection - about a third of the native fishes are in trouble.
Most estuaries are highly altered ecosystems and are experiencing declines in population numbers, affecting fisheries. However, few species are listed as endangered. The fauna may be quite resilient, as suggested by the striped bass in Chesapeake Bay. However, there is little hope for the Baltic Sea.
Marine
Fish are concentrated on the continental shelves where the impact of human activity flowing from the land is greatest. Fisheries are collapsing around the world as a result of overfishing. An additional problem with fisheries is the by-catch, the harvest of fish which are undersized and/or with not commercial value.
The aquatic environment is not static. It is dynamic, constantly changing, and always has. Fish have been dealing with global change for over 400 million years. As such, pressures from human populations are nothing new. Human impacts are severe because they add to natural variation, which has its greatest impact when populations are low. Such populations are then easily pushed over the edge into extinction. Based on the study of fossils, speciation events occur roughly every 5 to 12 million years. Natural extinction rates are slower.
Humans see the resilience, adaptability of living systems, and the way so many persist in spite of anthropogenic impacts. This resiliency is reflects the many levels at which fish systems have evolved to regulate functions and persist as habitats change. However, it is well known that sustained stress gradually degrades the ability of organisms to continue to absorb such stress. The result is typically a sudden, unexpected catastrophic failure that is irreversible.
The sustainable world catch has been estimated at 90 to 100 million metric tons per annum, a figure which was reached briefly, before declining to present catches of about 80 million metric tons per annum. The catch is continuing to decrease. Most destruction of fish stocks is for luxury trade rather than critical nutritional needs. Fish fill only 16% of global protein needs.
Effects of exploitation are often exacerbated by the models used in fisheries management. These tend to greatly overestimate catch by ignoring effects of stochastic events, and ignoring swings in population numbers over time.
It is not known if effects are reversible.
The largest accidental problems are occurring in inland waters, largely through the discharge of ballast water by ships. pollution facilitated invasion by alewife, smelt etc.
Exotic predators can cause very rapid changes in a fish fauna. Competition is implicated in declines of many native faunas. Exotics also tend to introduce new pathogens. When more competitive exotics can breed with native species, the native genotypes gradually come to resemble the introduced species.
Habitat alteration is probably the single largest cause of faunal change in freshwaters, and increasingly in the marine environment (includes effects of fishing gear). Factors are: modification of bottom type, channelization, dams, watershed perturbation, competition for water use, global climate change, and commercial exploitation of fishes. Freshwater Habitat alterations include damming, logging, grazing and other agricultural diversions and uses, filling wetlands, channelization etc.
Shipwrecks and other human debris are creating new reefs, and many are now created deliberately to increase local fish abundance.
Pollution is really a type of habitat alteration, but its scope and often subtle effects warrant its consideration as a separate human stressor.
Wild and stocked fishes living in public waters are normally considered the property of the general public. Farmed resources (aquaculture) may be privately owned but many hatcheries are run by agencies for the public good). Therefore, many conservation (and management) programs do not manage the fisheries resources directly but rather the manner in which people interact with the fisheries resource. Funds for the support of programs usually come from the general tax base and specific taxes on fishing gear and from fishing licenses.
Restoration/management practices may include the following: controlling the nature and extent of the harvest, providing advice to agencies on land- and water use issues, rearing and stocking fish to enhance depleted fish populations or to establish fishable populations, and manipulating fish communities of aquatic habitat to provide greater availability of fish species judged important by users.
Social and economic considerations may constrain the types of conservation programs that are feasible.
Family and community traditions are major factors among commercial fishers. Cultural ties are often important.
Most conservation programs focus on: 1) allocation of resources to user groups with the limit of the maximum sustainable yield and 2) protection of resources affected by land- and water-use activities. These are often in potential conflict, as well as their being conflicts among user groups in each category.
The following steps are required to conserve and begin restoring aquatic habitat and fishes in particular:
Economics Values
Most economic models give precedence to short-term economic gains over long-term sustainable use. There is much interest in using other systems based on ecosystem values, existence values, and intergenerational values.
Conservative valuations estimate ecosystems provide $33 trillion of services annually. This is $8 trillion greater that the GNP of all global economies. Coastal systems, such as estuaries, tidal marshes, mangroves, sea-grass beds, coral reefs, and the Great Lakes are valued at $8,000 t0 $9,000 per acre.year. These make up about 6.3% of the earth’s surface but represent about 43% of global services. These are also the most endangered of all ecosystems.
Some economists seek to put a monetary value - amenity values - based on recreational and esthetic value of natural habitat to humans. Many who will never visit various habitats value the fact that they exist.
A major problem with most economic theory is the assumption (implicit) that resources are treated as the property of the present generation, the current owners. As such they can, and should be, spent to produce immediate wealth, until gone. The alternative is to emphasize sustainability, and the equitable distribution of resources across generations.
Approaches to protect intergenerational values is to think in terms of:
Traditional market-oriented economists often do not accept as valid the ideas of safe minimum standards and natural capital, or any non-monetary valuation. An alternative is to waive economic argument. Instead, esthetic, scientific, cultural, teaching etc. values are sufficient for conservation and restoration.
Laws will not be sufficient to provide protection of biodiversity. Policy that sets the environment and private property at odds cannot endure. A system is necessary that values diversity. Holding multinational actors accountable for international and regional trans-boundary biodiversity standards may be the greatest challenge presently facing the global legal system.
The courts have, and will continue to have, difficulties in recognizing the ecosystem as a guiding principle for environmental law. The burden of proof for plaintiffs is too severe. The complexity of ecosystems, their fragility and slow rate of change confuse the legal system. Courts need dead animals, sick children, toxic pollution etc.!
