Anchovies on the market are getting smaller in size. Climate change and upwelling challenge ecosystems, fisheries and consumption
Photo: Spondylolithesis / Getty Images
Objective climate change continues to produce new negative and very worrying effects. The new case that emerges in the Mediterranean is that of anchovies, which are getting smaller and smaller, and are forced to move offshore in search of cooler waters, because the progressive reduction of sea currents cuts off their nourishment. These changes cause serious damage not only to these fish but also to tuna, sardines, and marine ecosystems in general. It is one of the effects of rising temperatures that threatens the biological engine of the Mediterranean, leading to a decrease in upwelling, or the emergence of the more nutrient-rich deep waters.
This is a fundamental naturalistic process: currents that bring deep, cold, nutrient-rich water to the surface. A true natural fertilizer that feeds phytoplankton, the basis of every marine food chain. Launching the new alarm is Confcooperative-Fedagripesca. “By 2050 there is a risk of a 20 percent reduction in upwelling phenomena,” warns Paolo Tiozzo, vice president of the trade association, "which will be less frequent, intense and effective than in the past, with cascading effects on fish, ecosystems and coastal communities dependent on fishing. Indeed, water stratification due to higher temperatures reduces the efficiency of upwelling of deep currents. Globally, upwelling areas cover only 1 percent of the oceans but provide up to 50 percent of the world's catch. In the Mediterranean, albeit less intensely, “the phenomenon is concentrated in specific areas that constitute real hotspots of marine productivity: these include the Strait of Messina, Carloforte in Sardinia, the eastern Adriatic coast and the Sicilian Channel.” Triggered by coastal winds, upwelling feeds phytoplankton and supports species such as anchovies, sardines and tuna. In the Adriatic alone, Fedagripesca points out, “this dynamic supports 40-60 percent of fish stocks.”
“When currents decrease,” Fedagripesca experts explain, "there are forced migrations such as those of anchovies, but also an increase in alien species from warmer waters and a drastic decrease in native species.
Why are anchovies, among the mainstays of the Italian pelagic fishery, getting smaller and progressively declining? These are objective facts that worry marine biologists, fishermen and environmental observers. What are the causes? Francesco Tiralongo, a marine biologist at the University of Catania and an authoritative expert on marine biodiversity and alien species, explains: “The reduction in the average size of the anchovy Engraulis encrasicolus is a well-documented phenomenon and is the result of a number of concomitant causes, among which the reduction in the extent of upwelling phenomena and overfishing stand out.”
Areas subject to upwelling are among the most productive for fisheries, both in the Mediterranean and in marine waters around the world. Upwelling, aided by warming seas, can severely affect ecosystem balances. Nutrient scarcity affects anchovies as well as other small pelagic planktivorous fish and limits their survival and growth. As a result, the entire population structure is affected, with smaller and less abundant adult anchovies. Also worsening the picture is fishing pressure, which acts selectively. Indeed, there is evidence that when individuals in a population are systematically and intensively fished, the stock shifts to smaller sizes over time. This is a classic overfishing effect.
We are dealing with cascading phenomena, involving the entire marine ecological network. The sea is a complex, nonlinear system: when a balance is altered, the consequences can be widespread and often unpredictable.
