October 2008, Issue No. 20
By Cammy Mills, Hood Canal Shore Stewards Coordinator. Additional content and editing by Doris Small, Washington Department of Fish and Wildlife.
A silvery Chinook salmon dancing at the end of a fisherman’s line or a brightly colored Sockeye making its epic journey up the river where it hatched, to spawn; when we think fish in the Puget Sound, these may be the kinds of images we first think of. But there is another kind of fish that we should think of too. While forage fish may not be as glamorous as some of our other local fauna, they fill a critically important niche in our local ecosystem.
Forage fish get their name, not because of their own foraging behavior, but because they are forage for other fish, birds, and marine mammals. Washington’s waters are home to six different species of forage fish (Pacific sardines, surf smelt, northern anchovies, eulachon, Pacific sand lance and Pacific herring). Of these species, three rely on nearshore waters of the Puget Sound for their survival. Surf smelt and sand lance rely on the upper beach habitat exclusively as spawning grounds, and Pacific herring spawn in subtidal eelgrass and macroalgae beds.
Because healthy forage fish populations are so vital to the stability of salmon populations (and other species) the Department of Fish and Wildlife has a “no net loss” policy for forage fish spawning habitat.
A critical link in the food chain
Most of you are probably familiar with the idea of a food chain, wherein smaller species become food for progressively larger species. If we use this food chain idea, then forage fish can be thought of as a vulnerable link in the chain. At the bottom of the food chain in Puget Sound, are phytoplankton (microscopic plants), tiny zooplankton (microscopic animals) and small invertebrates. These are then consumed by forage fish, which in turn, become food for various other fish-consuming animals, or piscivores (see diagram below). It’s important to note how few species are at the middle level of our chain, especially in comparison to the relatively large number of species that rely on the middle level of the chain for food. It’s also important to note that if the population levels in the middle of the chain are insufficient to support all the piscivores (fish eaters) at the top, the piscivores can not “choose” to feed on the species at the bottom of the food chain.
Figure 1. Simplified food web of piscivores in Puget Sound. Source: Forage Fish Management Plan: A plan for managing the forage fish resources and fisheries of Washington.
In food chains such as this, population size is not controlled from the top up, or the bottom down, but rather from the middle out. That is to say, if there is an abundance of organisms at the mid level (in this case, forage fish), then there will be an expansion in the population size at the upper level (because there is more food for them) and a decrease in population size at the bottom of the food chain (because they’re being eaten by the forage fish). Conversely, a shortage of organisms at the mid level will mean a population decrease at the top level and increase at the bottom level.
Much study has been devoted to the Pacific Herring and it is known that Pacific herring comprise a large percentage of the diet for many marine species, including Chinook, Coho, Pacific cod, whiting, lingcod, halibut and harbor seals. Other species including California sea lions, Stellar sea lions, harbor porpoises, Dall’s porpoises, Minke whales, pelicans, terns gulls and auks all use on forage fish for a significant part of their diet.
Forage fish populations naturally show rapid and wide fluctuations in size. This natural variability means that no management plan the humans devise can create a stable population, but it also means that we must be quite careful to preserve enough high quality habitat so that when there is a population crash, the species can recover. Once a population crash occurs, it may take decades for it to recover.
Forage Fish of Puget Sound
Pacific Herring
Pacific herring can grow to be nine inches long, are bluish to olive green on their back and have silvery sides. Herring spawn on eelgrass and macroalgae beds around Puget Sound. Herring tend to return to spawn in the same area as they were hatched, though their homing is not as precise as that of salmon. Herring originating from different spawning grounds are considered to be from a different stock. They spawn from late January through early April, with the exception of the Cherry Point stock in Whatcom County which spawns from early April through early June. To see a map of known herring spawning grounds in Puget Sound, click here.
Pacific Sand Lance
Sand lance (sometimes called candlefish) can grow to be eight inches long, have a gray to green back and silver sides. Their dorsal fin stretches almost the full length of their back and they have an elongated body. Sand lance feed in the open water during the day time, then bury themselves in the sand at night to avoid being eaten. Sand lance spawn on mixed sand and gravel beaches between the elevation of mean high tide and mean tide. They are obligate intertidal spawners, which means that if their preferred habitat is unavailable, they can not spawn successfully elsewhere. Sand lance spawn from November through February. Sand lance are very small and their eggs are miniscule, so even if you have them spawning on your beach, you may not see them. To see a map of known sand lance spawning grounds in Puget Sound, click here.
Surf Smelt
Surf smelt can grow to be nine inches long and have an olive green back with a silver or yellow band on their side. Surf smelt spawn on mixed sand and gravel beaches in the upper intertidal zone. In fact, both sand lance and surf smelt use the same stretches of beach at the same times of year. However, unlike sand lance, surf smelt have been found to spawn year round on some beaches. Surf smelt also use more of the upper beach than sand lance, spawning from the elevation of mean high tide to mean higher high water (the annual average of every day’s highest tide). Surf smelt eggs develop a small stalk that attaches them to the grains of sand on which they’re laid. This keeps the eggs from being washed away until they’re buried in the sand. This helps protect the eggs from predators. To see a map of known surf smelt spawning grounds in Puget Sound, click here.
What Can You Do
The areas in which our local forage fish spawn, make them especially vulnerable to impacts from shoreline development and there is no known way to replace lost forage fish spawning grounds. Additionally, not all forage fish spawning habitat may be known. Surveys for surf smelt spawning habitat are incomplete, so it is important to protect not only the known spawning beaches, but other beaches as well. Fortunately, there are steps you can take to help prevent degradation of forage fish spawning habitat, and in some cases, you may even be able to improve habitat.
Eelgrass beds can easily be damaged by boats that are anchored or moored in them. Anchors and attached chains can clear large patches of eelgrass when they scrape along the bottom as the boat they’re attached to moves about on the water’s surface. If you must moor or anchor your boat in an area with eelgrass, do so in deeper waters where there is no eelgrass (this has an added benefit as it also prevents the possibility that your boat will become grounded at low tide.)
Eelgrass is a plant and as such, it needs sunlight. Docks and piers can make it too shady for eelgrass to grow. If you are thinking about installing, or replacing such a structure, consider doing so in a way that permits light to pass through. For instance, when the Department of Transportation expanded the Clinton ferry terminal, they used glass bricks in the passenger walkway to permit light to pass through to eelgrass beds below. Installing glass bricks is potentially expensive. Less expensive techniques include using grating or limiting the width of your dock to 4-6 feet. Instead of building a new dock, you might also want to consider sharing a dock with a neighbor.
Poor water quality can also damage eelgrass beds. Runoff contaminated with fertilizer from gardens and farms is detrimental to eelgrass. There are many things you can do to reduce your use of fertilizer including, testing your soil prior to fertilizing to determine how much (if any) fertilizer your plants need, calibrate your spreader to make sure you only put down as much fertilizer as needed, amend your soils with compost to help boost soil health, and use organic or slow-released fertilizer. A buffer of plants between the water’s edge and your lawn or garden will help eliminate nutrients in runoff before it enters the water. Runoff containing pesticides can also damage eelgrass beds. There are many ways to eliminate weeds and pests without having to resort to harmful chemicals. For instance, you can pull weeds by hand and use mulch on garden beds to prevent their return, slug traps work well to eliminate slugs, and a strong spray of water is often enough to eliminate an aphid infestation on a plant. For more ideas on safe pest management, see the links for the Washington Toxics Coalition and the Northwest Coalition for Alternatives to Pesticide in the resources section.
Eelgrass beds also benefit tremendously from shorelines that are left natural. Bulkheads can increase wave energy and change a beach’s substrate so that the habitat is no longer suitable for eelgrass. If you are considering installing or replacing a bulkhead, consider soft armoring techniques instead and make sure that any structures you do build are set back as far as possible from the water’s edge. Not only does minimizing shoreline hardening help eelgrass beds, it also helps preserve the spawning habitat of sand lance and surf smelt. The increased wave energy and subsequent changes to a beach’s substrate and slope can eliminate both the type of substrate sand lance and surf smelt like to use to spawn and the tidal elevation at which they spawn.
One of the easiest things you can do to protect the area where sand lance and surf smelt spawn, is to provide shade on your beach. The eggs of both of these fish are vulnerable to drying out in warm temperatures. Studies have shown that the temperature on a beach is significantly lower where it is shaded by overhanging vegetation and that mortality rates for forage fish eggs on shaded beaches are much lower.
Creating a buffer of vegetation along your beach will help shade the habitat that is so vital for forage fish. Not only is this practice good for our local forage fish and eelgrass beds, it has the added benefit of helping stabilize slopes. Even if you don’t have a natural shoreline, planting a buffer along your bulkhead can help shade your beach.
So the next time you think about fish in Puget Sound, feel free to think of that beautiful silver Chinook, or brightly colored Sockeye, but then think about the forage fish that very likely fed those beautiful salmon, and know that you play a role in keeping those populations healthy.
Resources
Bargman, Greg. 1998. Forage Fish Management Plan: A plan for managing the forage fish resources and fisheries of Washington. Washington Department of Fish and Wildlife. Available at:
http://wdfw.wa.gov/fish/forage/manage/foragman.htm
Northwest Coalition for Alternatives to Pesticide, Pests and Weeds website:
http://www.pesticide.org/factsheets.html#alternatives
Penttila, Dan. 2001. Effects of Shading Upland Vegetation on Egg Survival for Summer-spawning Surf Smelt on Upper Intertidal Beaches in Puget Sound. Washington Department of Fish and Wildlife.
The Seagrass Conservation Working Group, Eelgrass Management Practices website:
http://www.stewardshipcentre.bc.ca/eelgrass/eelgrassrestoration.html
Washington State Department of Ecology, Puget Sound Shorelines Eelgrass website:
http://www.ecy.wa.gov/programs/sea/pugetsound/species/eelgrass.html
Washington State Department of Fish and Wildlife, Forage Fish website:
http://wdfw.wa.gov/fish/forage/forage.htm
Washington State Department of Transportation, Washington State Ferries, Eelgrass Protection Project website:
http://www.wsdot.wa.gov/ferries/your_wsf/corporate_communications/clinton_enviro/
Washington Toxics Coaltion, Healthy Homes and Gardens website:
http://www.watoxics.org/homes-and-gardens
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This product was funded through a grant from Washington State Department of Ecology. While these materials were reviewed for grant consistency, this does not necessarily constitute endorsement by the Department.
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