Southern Dolly Varden

Salvelinus malma lordi

Native Trout Fly Fishing

A stream resident Southern Dolly Varden from a stream in the Olympic Mountains of Washington State.

Introduction

The southern Dolly Varden subspecies of Dolly Varden are native to coastal watersheds from the Susitna River in Alaska southward to the Puget Sound in Washington. Despite their beauty and quality as a game fish, Dolly Varden are still recovering from a bad and undeserved reputation as ravenous predators of eggs and juvenile salmon. This resulted in Alaska putting a bounty on these fish for a time and ironically led to the extermination of far more rainbow trout and coho salmon than Dollies. Today it is understood that Dollies are indicators of the health of watersheds and that they typically pick of the weak and diseased eggs and fry.

Life History Information

Southern Dolly Varden exhibit four distinct life histories, anadromous, lacustrine, fluvial and stream resident. As general life history characteristics go, most adults generally reach sexual maturity at between the age of three and six years old. Dolly Varden are fall spawning fish and once they reach maturity, they typically spawn on an annual basis. Eggs hatch during the spring and alevin emerge from the gravel from late April to mid-May at around ¾” to 1” (20-25mm) long. Southern Dolly Varden fry primariy utilize small pools and eddies along stream banks where the flow is slower (Blackett 1968). In early summer, they can also be found in very small rivulets with depths of 0.5- 1.5 inches and widths less than 3 feet (Armstrong and Elliott 1972). After their first year of life, juveniles use a variety of habitats, including areas of still or moving water, gravel or muddy substrate, dense vegetation, or even in open water with little or no vegetation (Heiser 1966). Armstrong and Elliot (1972) showed that they appear to prefer undercut bank areas along the stream.

Isolated stream resident populations are relatively common at the southern end of the the Dolly Varden's native range. Fish from these stream resident populations are typically very slow growing and reach sexual maturity after three or four years old at a size of only 4" to 6". Stream resident Dollies tend to feed primarily subsurface on aquatic insects, but will take advantage of other prey items when available. Stream resident fish often remain in a rather short section of stream throughout their entire life, whereas fluvial individuals actively migrate to a larger stream to feed and overwinter. The fluvial fish will generally home back to their natal stream for spawning during the fall.

Due to their diet, most lacustrine Dolly Varden do not attain very larger sizes, and they generally weigh less than 1 lb (Amrstrong and Hermans 2000). The typical lifespan of these fish is around 8 to 10 years. Exceptions are Dolly Varden weighing up to 9 lb in lakes that contain kokanee, these larger fish feed on kokanee and tend to live longer, up to 19 years (Armstrong 1991). The typical diet of lake dwelling Dollies is primarily made up of invertebrates (aquatic insects), but they will prey on salmon fry when available. Some lacustrine populations of Dolly Varden also feed heavily on freshwater snails. This provides an important service as these snails host a parasite that is known to infect the eyes of juvenile coho and sockeye salmon and eventually cause blindness (ADFG 2006). Andrew (1975) showed that in lakes where southern Dolly Varden co-occurred with cutthroat the cutthroat tended to inhabit the surface waters while that Dolly Varden utilized the deeper waters of the lakes. However in lakes containing only Dolly Varden the fish were more of generalist and occupied all depths showing that the cutthroat tend to dominate over the Dollies when the two occupy the same lake.

Anadromous Dolly Varden are slow growing and generally spend three to four years rearing in freshwater before migrating to marine waters for the first time (Smith and Slaney 1980). During this period, before the fish out-migrate, they appear to use a variety of habitats and can be found in most accessible portions of the streams (Armstrong and Morrow 1980). The diet of these pre-smolts may include insects, eggs and salmon fry (generally pink and chum). Most smolt migrations occur during May and June, although some populations in SE Alaska have been shown to out-migrated during the fall (Armstrong 1970). Once in marine waters, Dolly Varden feed on a variety of items including capelin (50-75%), Pacific Sandlance (7-19%), polychaete worms (4-5 %), herring, crustaceans and salmon fry (Lagler and Wright 1962).It is typical for anadromous southern Dolly Varden to overwinter in lakes and Armstrong (1974) showed that fish from watersheds without lakes will often enter several streams while searching for one with a lake. Overwintering in lakes appears increase the survival and longevity of Dollies, as many of these lakes approach 32 degrees (F) during the winter, which means that little if any feeding is required for the fish to survive (Armstrong and Hermans 2000). Returning dollies tend to have rather high homing fidelity and are known to migrate into the uppermost reaches of their natal streams (Armstrong and Hermans 2000; Bryant et al. 2004). It is estimated that 70% of male and 50 to 60% of female sea-run dollies die after spawning and most males do not spawn more than twice, while the females may spawn three times (ADFG 2006).

Status

While southern Dolly Varden are susceptible to declines due to habitat degradation, they are still common and fairly abundant throughout much of their native range. Currently there are no populations of these fish listed on the Endangered Species act. The primary reason for this is that most populations occur in remote areas, leading to lower levels of exploitation This does not mean that Dollies haven’t seen declines as a variety of issues have lead to localized extinctions or population reductions. In British Columbia, Canada southern Dolly Varden are blue-listed, which means that this species is considered vulnerable. They are sensitive to habitat changes, including disruption of migration routes,sedimentation and increasing water temperature. Many populations have declined as a result of urbanization, dam construction, industrial activity, road building or over-fishing (including poaching) (BCMOF 2012). Southern Dolly Varden are especially susceptible to over-harvest, and in the Juneau AK area, over the period of only eight years, the catch rate dropped from more than four Dolly Varden per angler hour to less than 0.2 fish per angler hour (Armstrong 1991). Fortunately this problem can typically be remedied by more restrictive regulations.

Historically Dolly Varden suffered from a bad reputation as voracious predators of eggs and juvenile salmon, which led to a federal bounty being placed on them in Alaska between 1921 and 1939. The aim of this bounty was eradicate them from Alaska’s salmon bearing streams to increase salmon survival. With this bounty the government paid two to five cents per tail, however of the 6 million tails that were turned in, 71% were from coho salmon and 19% were from rainbow trout (Behnke 2002). It is now understood that Dolly Varden “predation” on salmon eggs actually provides an ecosystem service as free drifting salmon eggs die anyways and often become infected with fungi which posses a serious risk to salmon population (ADFG 2006). On top of that yearling coho and cutthroat trout are much more serious predators of juvenile salmon than Dolly Varden.

Habitat degradation may be one of the greatest threats to Dolly Varden across their range and clear-cut logging, stream channelization, and urban development are among the leading problems. The habit of young Dolly Varden to rear in small stream tributaries and even intermittent rivulets puts them at risk from certain types of development, especially logging. Improper logging practices can be extremely damaging, leading to increased sedimentation, stream temperatures and loss of cover. The problem is exacerbated by the extremely wet climate during winter months throughout this region, which increases the chances of landslides and other mass wasting events. Dry summers in the region can lead to elevated stream temperatures and even complete drying of streams that have been cleared of riparian vegetation. In the past it was a relatively common practice to “clean” streams of wood debris following logging events. However Dolloff (1986) showed that his practice led to a decrease in the carrying capacity of young coho and Dolly Varden in these streams. Such removal causes a reduction of pool habitat and an overall increase in the water velocity. Elliot (1986) indicated a substantial decrease in Dolly Varden numbers as well a decrease in body size in streams that had been cleaned of wood debris.

Description

The name Dolly Varden comes from a character in Charles Dicken's novel Barnaby Rudge, who favored brightly colored dresses. With the highly vivid colors that Dolly Varden are known to exhibit, especially as they near spawning, the name seems to fit. Both subspecies of Dolly Varden are often confused with bull trout and arctic char, which also occur across much of their range. In fact the name Dolly Varden was first applied to char from the McCloud River in California, which in actuality were bull trout. To the untrained eye, it often requires genetic analysis to differentiate from these other look-alike char. Despite this confusion, there are subtle differences in appearance that can help to identified Dollies in the field. The first of these would be the length of the jaw, which tends to be much shorter than bull trout’s and typically only extends as far back as the eye. The tail of Dolly Varden is rather squared off as compared to the forked tails of arctic char. The coloration of southern Dolly Varden can very to a great degree, but generally their background color is grayish-blue to green, with a yellow or orange/reddish color along the belly. Spots range from creamy yellow to a pink or red color. Anadromous individuals develop a silvery coloration that may mask their background color and spots.

Stream Resident Form

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Native Trout Fly Fishing
Native Trout Fly Fishing

Anadromous Form

 

 

Native Range

Native Trout Fly Fishing

A map of the original native range of the Soutern Dolly Varden. Data Source: Behnke (2002).