Overfishing and destructive fishing practices

By QAMAR SCHUYLER
Special to the Saipan Tribune

You may recall that a couple of weeks ago we ran an article summarizing the 10 most severe threats to the coral reefs. We promised to provide more information on each in upcoming pages. Here, then, is installment two of the threats to our reefs: Overfishing and destructive fishing practices.

Look up overfishing on the web, and you will get a range of definitions of the term. Some are stated in terms of the effects upon the natural environment, while others are more anthropocentric, and focus on how changes in the natural environment affect humans and how we manage “our” resources. Either way, overfishing refers to the practice of removing or harvesting too many fish, leading to the inability of the species to sustain itself.

You might be asking yourself how overfishing, or taking too many fish, could possibly have an effect on those rock-like corals. Well, all of the animals on a reef are part of an intricate web of life, referred to as an ecosystem. Just as in a spider web, if you disturb one strand (or take out one species), the integrity of the entire system comes into question. On an undisturbed coral reef, herbivorous fishes keep algal growth in check, so that the alga does not smother corals. Simultaneously, predatory fish feed on invertebrates, keeping the process of bioerosion under control. The term bioerosion refers to the gradual wearing away of the underlying coral reef structure by biological elements, such as boring worms and sponges. If the rate of bioerosion is too great, the corals become weaker and more likely to be damaged by storms or other physical impacts. Therefore, removing substantial numbers of fish from the system leaves corals vulnerable to a variety of threats. A recent article in Science magazine, compiling paleological, archeological, historical, and ecological data, shows that overfishing has severely affected coastal marine ecosystems worldwide, and pinpoints overfishing as the main cause of the decline of reefs.

So how are we doing here in the CNMI? Based strictly on the definition of overfishing used by the Division of Fish and Wildlife, there is no data showing that CNMI’s reefs are overfished at “a rate or level of fishing mortality that jeopardizes the capacity of a stock or stock complex to produce the MSY (Maximum Sustainable Yield) on a continuing basis.” How, then, can you account for those anecdotal accounts that you may have heard from fishermen, stating that the fish are smaller and harder to catch than they used to be? (for regular readers of this page, that’s another example of the shifting baselines phenomenon – www.shiftingbaselines.org). According to DFW scientists, there may be “local depletion” of certain species, meaning that in some specific areas, particular species might be in decline. Also, the scientists say, these anecdotal accounts go both ways. Some fishermen have reported that in the past few years, some of the fish they target have been getting larger and larger. In addition, DFW staff observed fishermen catching E’e’(juvenile Jacks) and Atulai (Scad), longer periods of time, rather than only in one particular season. The scientists credit the recent ban on net fishing, and the CNMI-wide ban on the use of scuba/hookah spear for this reported increase in numbers of fish for the Saipan lagoon.

Other data indicating potential depletion of resources are also not cut-and-dried. DFW scientists have documented increased imports beginning in the 1990s of fish from other islands such as Palau. This increase might be because stocks have declined enough that fishermen are unable to catch the fish they need live on. DFW believes that the gear ban that took effect in 2002 is a significant management step that addresses the local depletion of fish species, along with the CNMI-wide ban on scuba/hookah spear fishing, and the use of chemical and explosives for fishing.

However, the problem is that additional work needs to be performed specifically for nearshore fisheries in order to determine whether or not overfishing is happening for the island of Saipan. It is extremely difficult to collect the type of data required to prove that a single species is declining, let alone a whole ecosystem worth of species. Scientists are undertaking a number of studies that will hopefully provide that information. The interagency Marine Monitoring Team recently carried out a survey of the fish in the Saipan lagoon. Once the data have been analyzed, they can be compared to studies that DFW does within the no-take zones of the Marine Protected areas (such as Managaha). This will allow a comparison of fished and non-fished areas, providing another indication of the levels of depletion. In addition, DFW is about to hire 3 new staff to implement an inshore creel survey for Saipan Lagoon. This survey would poll fishermen about their catch and the amount of effort they put in, as well as collected species specific data on length and weight. The results of this survey, repeated over time, will also provide an indication of the stress on the resources. This topic is very complicated as there are a variety of ways to determine if a stock or stock complex are in need of more restrictive management measures.

DESTRUCTIVE FISHING

The phenomenon of destructive fishing, like overfishing, also has an enormous impact on reef systems in some parts of the world. In some areas, the practice of cyanide and dynamite fishing is demolishing reef resources. Like the name implies, cyanide fishers use the deadly substance to poison reef fish, forcing them to flee their hiding places deep within the crevices of the reef, right into the fishermens’ waiting nets. The cyanide not only stuns and confuses the fish, but also poisons the corals, ultimately leading to the decline of the ecosystem. Dynamite fishing is even more devastating. Fishermen create homemade bombs made from fertilizer, diesel fuel, and an empty beer bottle, and detonate them on the shallow parts of the reef. This technique also stuns the fish, some of which come floating to the surface of the water, and are easily harvested. In the process, it also flattens corals, destroying the crevices that juvenile fish hide in. It is also quite wasteful, as many of the fish killed are deep within the reef, inaccessible to the fishermen. Fortunately, these practices are not common within the CNMI.

Overfishing and destructive fishing, then, are one more human-induced threat to reefs worldwide. We must be careful to continue to collect scientific data and manage our valuable resources as best as we can. That is why it is essential to have the participation of all individuals who view, catch, market or utilize fishery resources for consumptive and non-consumptive purposes.

Schuyler is a Coral Outreach Specialist for the Coral Reef Management/Division of Environmental Quality/Division of Fish and Wildlife.