Monday, December 29, 2008

Forage Fish of Metchosin

Dec 13, 2008

If you take a walk along Taylor Beach you will often see river otters chasing each other through the waves and curious seals stare at you with their velvet painting eyes. Sea birds whirl and alight in the choppy grey sea. These animals provide some visual reference to the surrounding waters but the marine world is not one that is easily accessible to terrestrial creatures such as ourselves.
Just off the beach are large eelgrass beds and seaweed communities that provide crucial nursery habitat for juvenile fish, crabs and octopus. Under our feet as we walk on the beach, Pacific sand lance and (possibly) surf smelts lay their eggs in the high intertidal zone, forgoing their usual aquatic environment during their incubation.
They are known as forage fish, the cornerstone of the nearshore food web that supplies a critical food resource to commercial species such as salmon and cutthroat trout. Seals, sea lions, whales and seabirds, comprise part of the 100 species that are dependant on forage fish for their survival. A 2007 report states that “thirty five percent of the diet of juvenile salmon and sixty percent of the diet of Chinook salmon are comprised of Pacific sand lance”. Because they forage close to the shoreline, coastal cutthroat trout are heavily dependant on sand lance and surf smelts; fifty percent of our endangered humpback whales’ diets are sand lance. Marine birds are also dependant on these fish, there are estimations that seventy five percent of rhinocerous auklet’s food intake and fifty percent of the endangered marbeled murrelet’s diet are comprised of forage fish. Forage fish include Pacific herring, sardines, capelin, eulachon and northern anchovy as well as Pacific sand lance (aka needlefish) and surf smelts.
At night, Pacific sand lance (Ammodytes hexapterus) burrow in the sand as a means of escaping predators, sometimes surprising people walking at low tide along a beach, as they wriggle up from their nighttime “safe houses”. Some people will recognize them from the large, dense schools they form near the surface that are called “bait balls”. They spawn between November and February, more frequently in the late fall. Sand lance use their bodies to form small, shallow pits in sandy beaches, much like salmon redds, in which to deposit their spawn, which will hatch in four to five weeks. Both sand lance and surf smelts spawn during high tides, the upper beach must be covered in shallow water to facilitate egg deposition.
Surf smelt (Hypomesus pretiosus) can spawn at any time of the year, depending on weather, vegetation and probably many factors of which we are not aware. Surf smelt lay their sticky eggs in the high intertidal zone of a sand and gravel beach, just below the log line, usually between the two lines of deposited seaweed that are readily visible. Pea gravel sized stones, intermixed with coarse sand are preferred spawning material. Surf smelts who spawn in the summer make use of beaches with overhanging vegetation or areas with a continual underground movement of water (such as from a blocked stream slowly seeping through sand and gravel beds). These components ensure the smelt eggs will remain moist and viable under the hot summer conditions. Summer incubation and hatching happen within two weeks while cold winter conditions will increase the incubation time to one to two months. Surf smelt eggs can be found in small patches or they might cover miles of beach, depending on beach conditions and surf smelt abundance.
In order to ensure continued habitat for these important fish, it is important to understand how beaches are formed and maintained.
Bluffs and beaches form a type of unwitting partnership. The bluffs are subject to erosion because of their steepness, the type of material from which they are formed (clay, sand, gravel) and the force of wave action and storm events. Waves are powerful forces that continually act on shoreline materials. They pound against a bluff until it is undercut, when it will fall onto the shore, giving short term protection to the bluff. Slowly, wave action will distribute the fallen material, according to tides, currents and topography. The accumulation of these sediments on beaches and in shallow tidal ecosystems, provides habitat for many different species. Stormwater runoff and removal of bluff vegetation (especially to accommodate the desire for views), can dramatically increase the rate of erosion along bluffs.
Other creatures benefit from this eternal process. Under the cobbles of the low intertidal zone, in the area that is exposed only at low tides (visit the western end of Taylor Beach), you will find small squirming black eel-like creatures known as blennies. There are many species of blennies, some of which will lay their eggs under these cobbles. One or both of the parents will often remain to guard their developing young. At low tides, garter snakes and raccoons will descend from their land based territories and forage for blennies and other marine creatures. If you go searching for blennies, please respect their needs; lift the cobbles carefully and return them to their same positions.
It is not only the changes to rivers through logging activities, overharvesting and pollution from industrial and sewage contamination that has affected our declining marine stocks. Developments along shorelines, where we have not realized the cumulative effects of shoreline changes, have impacted heavily on the ability of marine species to survive. The bluffs to the west of Witty’s Lagoon are continually eroding and supplying sand to Witty’s beach. If you were to “harden” this area by erecting a wall to try to protect those slopes, you would eventually lose the beach.
A consequence of hardening shorelines, by building seawalls and other fortifications, is that the waves will now pound the adjacent shorelines with more force, causing a chain reaction of property owners hardening shorelines; the beaches that remain are scoured by the extra forces working on them and lose the soft sand and gravel that provide surf smelt and sand lance spawning habitat. Less spawning habitat = less forage fish = less food for the 100 species that feed on them.
If you have ever strolled the seawall around Stanley Park, or taken a boat cruise around Victoria’s shoreline, you will soon see that the beaches have been heavily impacted. Many of them have disappeared entirely or the high intertidal zones are gone or have been heavily scoured so that no spawning habitat remains. We are fortunate in that Metchosin has retained much of its forty-five kms of shoreline in relatively natural condition.
There are new “soft” techniques that have been developed to protect shoreline properties. Building natural formations such as sand and gravel berms, planting them with native shoreline grasses and trees, the placement of drift logs, all these mimic the natural barriers to erosion and contribute to maintaining our fish and marine bird and mammal populations.
Most of us might never see a forage fish nor would we recognize one if we did, but they are vitally important to maintaining the food web which feeds the more recognizable inhabitants of our marine waters. If you enjoy a meal of wild caught salmon or the sight of basking seals; consider using “soft” armouring techniques to reduce shoreline erosion and bear in mind, on your next walk along a beach, that under your feet could be the developing embryos of these valuable residents of our marine waters.
A group of Metchosin residents, under the guidance of Ramona de Graaf, biologist and BC’s most passionate expert on forage fish, has recently begun sampling along Taylor Beach, to search for evidence of Pacific sand lance eggs (sand lance are known to occur there) and surf smelt spawning. Eventually they hope to expand this initiative along other Metchosin beaches.

References and Resources:
• Coastal Fishes of the Pacific Northwest, 1986. by Lamb and Edgell
• Protecting Nearshore Habitat and Functions in Puget Sound: An Interim Guide

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