SEVENSEAS Marine Conservation & Travel Issue 17, October 2016 - Page 33

consumption would not be in the form of fish. In Pauly’s original scenario, future humans would inevitably be eating plankton soup and the aforementioned jellyfish sandwiches as our oceans’ ecosystems and species populations are drained, all due to our desire for affordable seafood.

Pauly’s original paper came out almost 20 years ago and, thankfully, jellyfish sandwiches have not yet come to fruition. There still remains a spirited debate whether “fishing down”, as Pauly originally conceptualized it, is occurring at all; after all, many of the world’s largest fisheries have always targeted valuable invertebrate species. In the Gulf of Thailand, for example, fisheries commonly seek out the most accessible marine species first since they are easiest to catch. These species are usually ones closest to shore, and mainly consist of mussels, shrimp, and smaller fish. Only once those resources are exhausted would many fisheries in the Gulf of Thailand begin to fish for larger species higher up the food web, creating an opposite “fishing up” effect in that region. Additionally, some top species, such as oceanic white tip sharks, are not targeted by fishers but are commonly taken as by-catch from other fishing efforts. In the Gulf of Mexico, ironically, oceanic white tips are usually ensnared in shrimp trawls; there, the targeting of invertebrates actually leads to a fishing down effect! Other factors such as climate change, technological innovation, and economic incentives also certainly play a part in which marine species fisheries target.

Nevertheless, there is real evidence of fishing down the food web in many important fishing regions, and this holds enormous implications for our oceans’ invertebrate species. Formerly-common top predators like the Atlantic cod have been fished out of existence in many regions like the U.S. and Canada. According to the California Department of Fish & Wildlife, recorded invertebrate landings in the Eastern Pacific have increased by over 400% since 1950 while finfish landings have lagged behind or declined. As an example, California’s fishing industry has always relied on invertebrate species like Dungeness crab, market squid, and the sought-after California spiny lobster to constitute a substantial portion of its overall landings and revenue. What has happened to these industries in the past few decades, however, is telling; these three species have quickly become the three most valuable fishing stocks in the entire state, and it’s not even close. Since 1980, the total value of finfish in Southern California fisheries has declined from 80% to just 6%, while invertebrate value has increased from 4% to almost half. Fishing down the food web has contributed to an overall dramatic increase in invertebrate fishing in California, and a dramatic decrease in traditional finfish captures.

The thought of eating more Dungeness crab and spiny lobster may not seem so bad at first glance, but at the end of the day, when will the fishing down effect cease? What will prevent us from fishing these invertebrate populations out of existence as well? Eventually, this trend may very well lead us to something resembling jellyfish sandwiches. More importantly, the complex relationship between species in the food web means that any change in these populations has many chain reactions that affect the entire ecosystem. Invertebrates in any ecosystem may be impacted by the removal or addition of predator species, food species, or competitors, and these changes can lead to population explosions or collapses. Our oceans’ valuable ecosystems are fragile, and how we maintain them will determine the viability of invertebrate populations as fishing pressures increase.

SEVENSEAS - 33