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Fish

Fish remains are readily identifiable components of garbage worldwide, if for no other reason than their smell, yet the contribution they make to the amount of garbage that accumulates is difficult to calculate. Fish bones are relatively delicate compared to those of land animals and do not stand up as well to post-depositional chemical and mechanical processes.

If one were to excavate, for example, a five-year-old garbage dump and tally up the number of fish bones recovered, they would be underrepresentative of the original number. In addition, an unknown—but large—percentage of fish never make it to land but are dumped dead back into the waters from which they were caught. Likewise, fish are often processed on or near the water, with the by-products never reaching land.

Calculating Waste

Perhaps the only method available for calculating the contribution of fish remains to garbage is to use catch figures as a baseline and then examine those figures against known or suspected patterns of human consumption. Annual worldwide fish production, including wild capture and aquaculture (farm) production (excluding shellfish) averages around 140–150 million tons. This figure is susceptible to the vagaries of any number of variables, including price and ecosystem disruptions, especially climate anomalies such as El Niño. Although precise production figures from China are unreliable, that country accounts for approximately 30 percent of the world's fish production, followed distantly by Peru, the United States, and Japan. Of the total tonnage of fish processed each year, 70–75 percent are for human consumption and 25–30 percent are for reduction into fishmeal and fish oil. Fishmeal, which is a coarsely ground powder made from cooked fish, was once important as a fertilizer but is used primarily in pet food in the 21st century. Peru is the leader in fishmeal production, using the Peruvian anchoveta, which is the leading fish caught in the world in terms of tonnage.

Worldwide, annual per capita fish consumption is about 35–40 pounds. In some Asian and African countries, where fish provide 50 percent or more of the animal protein, annual per capita consumption can run as high as 45–50 pounds. In some small island states, such as Seychelles, the annual per capita consumption can exceed 165 pounds. In other countries, especially meat-exporting countries such as the United States and Argentina, annual per capita consumption of fish is under 20 pounds. Based on these figures, one can roughly estimate that annual per capita fish waste worldwide is about 10 pounds.

Fish Smell and Its Effects on Garbage

Rotting fish produce one of the most noxious smells imaginable, in large part a result of adaptations that fish have made to aquatic environments over millions of years—adaptations that are vastly different than those made by land-living animals. Fish contain an odorless chemical called trimethylamine oxide (C3H9NO). Once a fish dies, bacteria in the body begin breaking down the compound into two foul-smelling compounds, putrescine (C4H12N2) and cadaverine (C5H14N2). The meat of land animals contains far less trimethylamine oxide than that of fish and hence does not smell as putrid when decaying. There is considerable variation in trimethylamine oxide levels even in fish, with cold-water species, especially those that feed near the surface, having the highest levels.

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