Fishing industry and global warming

Definition

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.

Significance for Climate Change

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. US Environmental Protection Agency representatives voiced concerns that climate deviations affected the quantity and quality of fisheries to the US 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 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 1980s, Massachusetts fishers 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 1990s 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 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 in the atmosphere, bleaching coral reefs, which many fish need for habitats and nurseries. According to a study published in PLOS Climate in 2023, ocean acidification may prevent growth in juvenile Atlantic sea scallops, a $670 million market in 2021. However, a January 16, 2009, Science article reported researchers’ discovery that in fish fecal material can control some ocean acidity. CO₂ circulating in fish blood stimulates the 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. The World Bank supported a different approach in an article in 2024. Scientists there believed that strong fishery management was key to combating global warming. They argued that preventing overfishing was key to

battling climate change. Ensuring healthy populations of fish species would provide a buffer against those lost because of high water temperatures. They also recommended keeping ecosystems healthy and expanding marine protected areas and fish nursing grounds.

Bibliography

Marine Resources Service, Fishery Resources Division, FAO Fisheries Department. Review of the State of World Marine Fishery Resources. Rome, Italy: Food and Agriculture Organization of the United Nations, 2005.

Kaczan, David, Fegi Nurhabni, and William Chang. "How Water Rising: Climate Change's Impact on Fisheries (and What to Do About It)." World Bank, 29 Apr. 2024, blogs.worldbank.org/en/climatechange/hot-water-rising-climate-changes-impact-fisheries-and-what-do-about-it. Accessed 17 Dec. 2024.

Nelleman, Christian, Stefan Hain, and Jackie Alder, eds. In Dead Water: Merging of Climate Change with Pollution, Over-Harvest, and Infestations in the World’s Fishing Grounds. Arendal, Norway: United Nations Environment Programme, GRID-Arendal, 2008.

Pousse, Emilien, et al. "Juvenile Atlantic Sea Scallop, Placopecten magellanicus, Energetic Response to Increased Carbon Dioxide and Temperature Changes." PLOS Climate, 22 Feb. 2023, doi.org/10.1371/journal.pclm.0000142. Accessed 17 Dec. 2024.

Robbins, Jim. “As Fight for Water Heats Up, Prized Fish Suffer.” The New York Times, April 1, 2008, p. F4.

Sharp, Gary D. Future Climate Change and Regional Fisheries: A Collaborative Analysis. Rome, Italy: Food and Agriculture Organization of the United Nations, 2003.

Wilson, R. W., et al. “Contribution of Fish to the Marine Inorganic Carbon Cycle.” Science 323, no. 5912 (January 16, 2009): 359-362.