Have you ever wondered about who eats who out in the open ocean? We know there are some epic fights outside of the ocean – Rocky Balboa vs. Apollo Creed, cats vs. dogs, white vs. wheat bread – but are there any between fish?
Teams of scientists around the world are devoted to answering this very question. The ‘who eats who’ of the ocean is called its trophic structure (commonly referred to as a web). Studying trophic webs allows scientists to better understand the roles each animal plays in the larger marine ecosystem.
On the West Coast, lingcod and rockfish are two species noted for their ecological importance, as well as their importance to commercial and recreational fisheries. Noted for their flavorful meat, in recent years populations of both fish have declined due to overfishing.
To combat this decline, managers have established fishing restrictions for both species and created rockfish conservation areas (RCAs) where no fishing is permitted. These conservation measures have helped lingcod populations rebound back to healthy levels.
Unfortunately, rockfish populations have not experienced similar success. Scientists believe that this may be due to their slower growth rate.
A recent study by researchers at the University of Washington, in collaboration with The Nature Conservancy and local fishermen, examined the role of lingcod in the recovery of overfished rockfish.
The bad news. This study identified a combination of three factors contributing to the delayed recovery of rockfish:
- It turns out that lingcod preferentially feed on young rockfish
- Commercial fishing vessels still target rockfish, but at much lower rates set by fishery managers
- Rockfish have a very slow growth rate (as mentioned previously)
It is the combination of these three factors that has left rockfish unable to fully recover. The study also suggested that lingcod predation on rockfish is exaggerated within RCAs because there is no fishing controlling predator populations.
The very areas meant to serve as a safe haven for rockfish are now quite the opposite. They’ve become battle grounds for lingcod and rockfish. And unfortunately, the rockfish are losing.
The good news. Now that the trophic relationship between lingcod and rockfish is understood, fisheries scientists and managers are able to keep a close eye on it. In fact, this study demonstrated that fishing for lingcod within an RCA can actually be beneficial for rockfish.
By fishing with selective gear, lingcod may be targeted without harming rockfish populations. Not to mention, allowing limited and controlled fishing for lingcod within these RCAs would also benefit fishermen and consumers – fishermen can access healthy lingcod stocks and consumers can buy this tasty lingcod at market.
Moral of the story. By examining trophic relationships and ecosystem dynamics, scientists and managers are employing ecosystem-based fisheries management (EBFM). EBFM is aimed at maintaining ecosystems in a healthy, productive, and resilient condition that benefits all species – including humans – using the resource.
Watch for our upcoming post on EBFM. We’ll discuss the framework, as well as its strengths and weaknesses in much greater detail in a future post.
Next time you find yourself daydreaming about fish tacos, remember that there’s an entire ecosystem out there made up of fish engaging in epic battles under the water. And the fish that’s on your taco? Well, it may have been the Rocky Balboa of the ocean in order to make its way to your plate!