Fish Farming Essay

Fish have been a protein source throughout history. Early fishing primarily involved individuals capturing fish near their communities for consumption or trade. Ships gave fishers access to ocean-based fisheries. Commercial fishing became industrialized by the late nineteenth century, as technological innovations helped locate, catch, and process fish. In addition to fish living in natural freshwater or saltwater fisheries, fish cultivated in fish farms’ ponds or tanks represented approximately one-fourth of the fish eaten in the world. Countries benefited economically with domestic trade and by exporting valuable fish.

In the early twenty-first century, fisheries generated billions of dollars globally with approximately 42 million people employed to catch fish and several hundred millions more working in related industries. Fisheries reinforced food security when climate changes caused shortages of other agricultural products.

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For centuries, fishers realized that weather affected fish populations, but they lacked the scholarly resources to investigate their observations. During the nineteenth century, fishery researchers began applying scientific methodology to study diverse factors affecting fish health, reproduction, and habitats.

They contemplated reasons for decreased fish populations besides overfishing. U.S. Environmental Protection Agency representatives voiced concerns that climate deviations affected the quantity and quality of fisheries to the U.S. Congress in 1988. The American Fisheries Society promoted research examining how climate change might affect fisheries. Scientists consulted ships’ logs and records documenting fish-catch statistics and meteorological patterns to evaluate hypotheses about the climate’s possible role in fish population losses. Researchers used computer simulations to consider future climatic factors that could potentially harm fish.

Fish are exceptionally vulnerable to habitat changes. The World Wildlife Federation emphasizes that temperature increases of 2° Celsius or more are dangerous for fish. Healthy water temperatures differ according to species. Scientists link increased water temperatures to global warming, because water absorbs heat trapped by greenhouse gases (GHGs). The Intergovernmental Panel on Climate Change (IPCC) states that abnormally high ocean temperatures have occurred as deep as 3,000 meters below sea level. Water-temperature increases can interfere with fishes’ oxygen supply and the physiological processes associated with maturation, digestion, and spawning. High temperatures also weaken fishes’ resistance to toxic substances and pathogens that invade their habitats. Scientists evaluate fish otoliths (ear bones), which indicate growth, to study how temperatures at varying depths influence development.

Researchers have correlated temperature deviations in oceans with fish displacement due to reduced growth of food sources, such as plankton. Melting glaciers caused by global warming raise water levels and dilute the oceans, decreasing salinity. This surplus water disrupts currents crucial for transporting food and removing pollutants, including from such human sources as fishing vessels and fish-factory emissions. Fish migrate to waters with more compatible temperatures and ample food supplies, but they often fail to thrive if they are unable to adapt. Since the late 1980’s, Massachusetts fishermen reported an 80 percent decline in cod catches. Fisheries managers aware of areas where wild fish have relocated can adapt management practices to minimize additional climate change damage and to replenish fisheries.

Temperature increases of almost 3° Celsius in some locations have caused freshwater in streams, rivers, and lakes to evaporate, reducing habitat size and stressing fisheries, particularly trout and salmon species in the western United States. In Montana, grayling fish in the Big Hole River decreased from ninety-six fish per kilometer of river in the 1990’s to as few as eight in the early twenty-first century because of temperature changes. Some hardier species, such as smallmouth bass, sought warmer habitats, competing for resources and displacing indigenous fish. Scientists warned that loss of diverse fish genetic material diminishes fisheries and some species will become extinct. Fishery experts estimated reductions of approximately 90 percent of bull trout and 40 percent of salmon populations by 2050 if extreme heat and arid climate conditions persist.

Climate changes alter fish ecosystems in lakes, resulting in fishery populations being reduced by as much as 30 percent, as has been reported in Africa’s Lake Tanganyika. In addition to temperature and precipitation deviations, climate changes slow wind velocities needed to stir nutrients from deeper lake water to the surface. Changing climates might force fish farmers to relocate stock from ponds to protected sites where hot temperatures do not threaten fish health.

Oceans become more acidic when water absorbs carbon dioxide (CO2) in the atmosphere, bleaching coral reefs, which many fish need for habitats and nurseries. A January 16, 2009, Science article reported researchers’ discovery that calcium carbonate in fish fecal material can control some ocean acidity.CO2 circulating in fish blood stimulates production of calcium carbonate. Ironically, as GHG emissions increase, the amount of fish-produced calcium carbonate might too, helping counter climate change’s impact on fisheries.

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