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What Are Forage Fish?

The importance of forage fish both to marine eco-systems and the various industries - fish oil and meal, Omega 3 supplements, etc. - is one of the issues IFCNR is currently following with growing concern. The increasing demand for products based on forage fish raises questions about the effect forage fisheries have on the marine food chain and those species dependent upon them.

The following article published by The Fish Project of the Oregon Institute of Marine Biology is reprinted to provide an excellent backdrop against which IFCNR can begin to discussion of this topic.

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Forage fish are pelagic, planktonic feeding fish which provide a main food source for many marine animals. Examples of forage fish include sardines, anchovies, herring, menhaden, squid, krill and smelt (species specific information on these fish). Forage fish are important both for humans and for the ecosystem which they are a part of. These small, abundant fish are harvested for use as bait, fertilizer, feed for aquaculture, and human consumption. In the ocean, forage fish play a vital role in marine ecosystems. They serve as a momentous link between lower and higher trophic levels. Many birds, fish and marine mammals rely on forage fish as their main source of prey. Because of their small size and susceptibility to predation, these fish often form schools, by which some predators have evolved to create intricate strategies for “surrounding” or “cornering” these schools of fish. Predators, such as salmon, are important to humans and society. Knowing how to sustain forage fish populations is valuable to sustaining the populations of their predators.

The harvest of forage fish can be dated as far back as 3000 years. Throughout history, populations of forage fish have been unscathed due to the abundance of fish, the limited amount of fishing vessels, and modest fishing techniques. During the mid-20th century, some major fisheries in the world showed a marked decline. With the combination of this abatement and the recent advancement in fishing techniques, we began "fishing down the food web" (Pauly et al., 1998). In other words, we shifted our focus from large, apex predators to species lower in the food chain which were, at the time, quite abundant. If we continue to exploit forage fish at our current rate, recovery of larger fish will be problematic in that their main food source will be depleted. In this page I will further discuss the uses/importance of forage fish, their fisheries, and the predicaments faced with proper management.

Forage fish are critical in marine food webs. They provide the necessary transfer of energy from primary and secondary producers to large, apex predators at the top of the food chain. Most marine species directly or indirectly depend on healthy forage fish populations. The marine food web including forage fish is often referred to as a "wasp-waist" ecosystem, defined by a large number of species in the lower trophic levels (plankton), a large number of predatory species (e.g. salmon, marine mammals, seabirds, etc), and a critical mid-trophic level (plankton-feeding) occupied by one to several species (Bakun et al., 2010). Unlike many terrestrial ecosystems, wasp-waist ecosystems exhibit neither top-down or bottom-up control but instead top and bottom control from the middle (Bakun et al., 2010). This means forage fish dynamics can have cascading influences above and below their level in the food chain.

Forage fish are essential in marine food webs and are economically important. Harvested forage fish are processed for a number of uses including bait, fertilizer, human and domestic animal food, fish oil, and fish feed. In recent decades many economically important fisheries have collapsed due to overfishing, including the Atlantic cod (Bakun et al., 2009). Many of these fisheries are geared towards fish which feed at or near the apex level, fish which rely on forage fish. To compensate for the loss of big fish fisheries, a growing interest in aquaculture has arose. Aquaculture is the farming of aquatic animals in natural or artificial settings. Fish such as salmon and tuna are being artificially bred across the globe to support a growing human population and a high demand for seafood. With an increased interest in aquaculture there is a higher demand for forage fish as a source for feed. A large portion of forage fish catches are used in aquaculture, much of the rest is used as feed for terrestrial farm animals such as pigs and chickens. When examining efficiencies of farmed fish production, researchers often use a conversion ratio which compares the amount of wild fish used for feed (input) versus the total harvested farmed fish (output). This ratio has fallen by more than one-third since 1995 (Naylor et al., 2009), but is still high enough that forage fish populations are being depleted in order to accommodate for the growing aquaculture industry.

With the depletion of large fisheries and the increasing need for forage fish for aquaculture feed, we have begun to concentrate fishing efforts on forage fish. Since forage fish are pelagic and swim in schools, they are very susceptible to modern fishing techniques. These techniques include purse seines and mid-water trawls, which trap these schools in excessive numbers. For more information on these fishing techniques you can visit the Monterey Bay Aquarium website for descriptions and animations of purse seining and trawling nets- Fishing Methods.

Forage fish have contributed anywhere from 50-64% (1950-1994) to the total marine catch (Cury et al., 2000), and this percentage has since increased. In past times there was not much economic incentive to fish for forage fish, but when larger fish are fished out and there is demand from aquaculture,forage fish fisheries now dominate the commercial fishing market. If we were harvesting forage fish solely for human consumption, the harvested catch would probably be a sustainable amount. But the amount of forage species caught for human consumption is relatively small compared to the amount harvested for other uses. The life cycles and ecological significance of forage fish is just recently gaining researcher's interest. Researchers are now realizing the importance of these fish for marine ecosystems. Currently, forage fish are being over-exploited, if their populations are to be saved we must start implementing strict and intelligent management policies.

Alternating Dominance

Regions are often occupied by one to a few species of forage fish. Because the life spans of these fish are so short, they often exhibit boom and bust populations where population sizes will oscillate substantially. Species of forage fish exhibit alternating dominance over “multi-annual time scales” (Bakun et al., 2009). For example, in Peru, anchoveta nearly disappeared around 1975, and around this time sardines became quite abundant. As was later noted, this was in part caused by an El Nino event. The causation of this alternating dominance can be attributed to a combination of climatic events, populations dynamics and in some cases, overfishing. This phenomenon may effect what species is targeted by fishermen (graphically exemplified above). Understanding of this alternating dominance is crucial in creating catch limits and fishing regulations for forage fish and their predators. With natural population fluctuations, sardine numbers may be substantially low one year, and if that is combined with intensive fishing pressure, the results may be drastic. It is imperative that we call for what is known as ecosystem-based management when regulating forage fish fisheries. Ecosystem-based management rejects our often adopted “tunnel-vision” where management only focuses on the target species when setting up fisheries management. Instead, a holistic vision needs to be utilized by looking at the ecosystem as a whole, its connectedness and heterogeneity, as well as other abiotic and biotic factors such as climate and habitat change.

Management

There are numerous factors currently threatening forage species, many of them are influenced by human activity. Climate change, fishing pressure, ocean acidification, and pollution all modify forage fish populations. The majority of our forage fish fisheries are over-exploited or recovering from over-exploitation (Naylor et al., 2009). While forage fish exhibit natural oscillations in their range and population size, humans are creating substantial changes as well. The current level of management for forage fish is inadequate, management plans have been created for a few economically important species but policies have neglected other species which have lower economic values and whose ecological influence is not known. From a federal perspective, The National Marine Fisheries Service (NMFS) is the main agency responsible for marine resource stewardship. The Pacific Fishery Management Council (PFMC) works closely with advising the NMFS on US West Coast fisheries management. Their management plans cover target and non-target species. For example, NOAA banned krill (krill is not exactly a forage fish but was defined as one so it could be included in forage fishery management plans) fishing in 2009 after a recommendation from the PFMC and NMFS who recognized the necessity for krill as an important prey species for many marine animals including salmon and blue whales. Though there are adequate management plans being implemented, there is a lack of management for many other important forage species. The main implication with forage fish fishery management is the uncertainty in abundance estimations and the lack of buffers in management plans (OCEANA, 2011).

On the East Coast, fisheries are managed by the Atlantic States Marine Fisheries Commission (ASMFC). The commission was formed in 1942 and consists of 15 Atlantic Coast states, the Commission operates on a one-state, one-vote system. Their mission is to better utilize and manage their marine resources, as a Commission their ideology is that collectively they can accomplish more than an individual state can.

The ASMFC regulates near shore fishery resources including shellfish, marine and anadromous fish. As far as forage species go, the ASMFC is currently managing the Atlantic menhaden, Atlantic herring, Spanish mackerel, shad, and river herring. Some of these fish exist in state and federal waters, in these cases the ASMFC works with the East Coast Regional Fishery Management Councils and the NMFS to develop fisheries management plans.

Overall, current management is insufficient. While there is growing acknowledgement about the importance of forage fish to the ocean's ecosystems, fisheries are still in full force. So many marine animals rely on forage fish as a main food source and they are now facing another competitor, humans. The federal government, the PFMC, and the ASMFC are taking a step in the right direction and should further their efforts to implement more management policies. In a report by OCEANA, they addressed the importance of forage fish for the oceans ecosystems and came up with a set of solutions for forage fish conservation; (1) No new fisheries for forage fish, (2) Set conservative limits for forage fish fisheries and save 10 percent for climate impacts, (3) Protect breeding hotspots, (4) Prioritize uses for forage fish-- place ecosystem needs first (2009). To do this we need to either lessen our dependency on aquaculture or find an alternative source of feed for farmed fish. Aquaculture is pushing the limits on how much pressure we can put on these critical populations.

The Pacific sardine fishery was the largest fishery in the world during the 1930s and 1940s with an annual landing of 600,000 metric tons (MacCall, pg. 48). Strict regulations were put into effect by the California Department of Fish and Game (CDFG) in the late 1940s in lieu of a drastic collapse in the fishery. Subsequently, members including Scripps Institution of Oceanography (SIO), the federal governments Fish and Wildlife Service (FWS), and the CDFG, formed the California Cooperative Oceanic Fisheries Investigation (CalCOFI). Their mission was to find the cause of the collapse. Within members of the CalCOFI there was much debate as to what stimulated the collapse of the Pacific sardine, and focused actions failed to be implemented. As seen in the graph, sardines were not caught at all in the 1952/1953 season. The debate continued until 1957-59 when a strong El Nino occurred and suddenly sardines reappeared in California. This re-occurrence led scientists to believe that environmental conditions were a major influence on the fishery, though others did not. In 1974 sardine populations were down again and California’s sardine fishery was closed. Scientists continued working to resolve the mystery to this phenomenon. Not until the 1980s was it observed that variance in sardine populations occurred in unison around the world, when sardine fisheries reappeared simultaneously around the world (MacCall, pg. 52). This observation gave scientists confidence in finding the underlying cause of sardine population fluctuations.

By the 1980s sardine populations were steadily increasing and reaching a “healthy” level. The California Pacific sardine fishery was reopened in 1985 with strict regulations and close monitoring. With the Pacific sardines increasing in abundance as well as other sardines reappearing around the world, scientists tried to make connections with climate fluctuations. By the 1990s it was clear that El Nino patterns (which affected water temperatures) had some influence on sardine/anchovy populations. During this time studies were conducted with Japanese and Pacific sardine which gave conclusions that recruitment (reproductive success) was highest in warm water conditions and lower in colder conditions. Utilizing this crucial information, a California fishery management plan was created in 1998 which combined catch limits with environmental factors. First, there was a set minimum reserve of 150,000 metric tons (mt), this means sardine populations could not go below this set number. The plan stated that during warm ideal conditions 15% of the biomass in excess of 150,000 mt was allowed to be harvested and only 5% allowed during cold conditions.

In conclusion, the collapse of sardines in the 1950s cannot be attributed to one cause. It is believed by many that the collapse was due to a number of causes including overfishing and environmental conditions. This is a major lesson in fisheries management, that there is always more than one, sometimes several, factors affecting fish populations. These factors include overfishing, environmental changes, pollution, population dynamics of predators/prey, and habitat loss. Ecosystem-based management is meant to include all of these factors when constructing management policies.

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