El Niño is a natural climate phenomenon marked by warmer-than-average sea surface temperatures in the central and eastern equatorial Pacific Ocean. These oceanic changes significantly impact marine ecosystems, especially in the Pacific, and subsequently affect fishing activities. Understanding these shifts is important for communities and industries reliant on marine resources.
How El Niño Alters Ocean Conditions
El Niño significantly alters ocean conditions, starting with widespread sea surface temperature (SST) anomalies. The central and eastern equatorial Pacific experiences warmer SSTs, often exceeding 0.5 degrees Celsius above average, which can extend to other regions. This warming influences heat distribution and water movement.
A primary change is the suppression of upwelling, where cold, nutrient-rich deep ocean waters rise to the surface. Normally, this process supports abundant marine life, especially along the coasts of Peru and Ecuador. El Niño weakens or halts upwelling, reducing the supply of nutrients to surface waters.
El Niño also alters major ocean currents. The normal westward-flowing trade winds weaken, allowing warm surface waters to spread eastward. This shift redistributes heat and affects marine species’ pathways.
Disruption to Marine Life and Fish Populations
Altered ocean conditions during El Niño directly disrupt marine ecosystems and fish stocks, mainly by impacting the marine food web. Suppressed upwelling reduces essential nutrients, decreasing phytoplankton abundance. Since these microscopic plants form the food web’s base, their decline impacts zooplankton and the fish that feed on them.
Many fish species, sensitive to temperature or reliant on specific food, exhibit significant migration and distribution shifts. Cold-water species may move into deeper or northward waters for cooler temperatures and more food. Some warm-water species extend their ranges.
This leads to a scarcity of traditionally fished species in certain regions as their usual habitats become less suitable. For example, Peruvian anchovy moves to deeper, cooler waters during El Niño.
Warmer waters also stress fish, impacting their reproductive cycles and increasing mortality rates. Species adapted to cooler environments are vulnerable to thermal stress. Some fish populations experience reduced growth, reproduction, and survival rates during El Niño.
Direct Impacts on Fishing Practices
The scarcity of fish populations during El Niño directly reduces catch rates for commercial and artisanal fishers. When fish migrate or their numbers decline, boats return with smaller hauls, impacting livelihoods. For example, Peru’s industrial landings saw a 50 percent reduction in 2023 compared to 2022 due to El Niño.
Reduced catches lead to economic losses for fishing communities and the broader industry. Countries reliant on fisheries, like Peru, face billions of dollars in losses, affecting income, employment, and export revenues. The 2023 anchovy fishing season in Peru was described as the “worst in the last 25 years” due to El Niño.
Fishers often change their target species, focusing on those still abundant or shifted into their grounds. This adaptation can disrupt markets as traditional species dwindle and new ones become prevalent. Shifting target species also introduces processing and marketing challenges.
Operational challenges also emerge. Fishers may need to travel farther to locate viable fish stocks, increasing fuel costs and eroding profit margins. Adapting fishing gear for different species or conditions can incur further expenses.