6-14-09

The Smelt and Alewife May be at Low Levels but other Baitfish are Increasing

As was discussed in previous newsletters, the smelt and alewife populations are low but there has been a dramatic increase in a new baitfish, the exotic round goby.  In addition, the MDNR is attempting to reestablish the cisco, which historically was the most common native forage (baitfish) present throughout Lake Huron.  Below is a discussion of each species.

The Round Goby is Becoming Established in Lake Huron

The round goby is a new exotic baitfish in the Great Lakes that is readily eaten by many species of fish including lake trout, brown trout, rainbow trout, whitefish, walleye, yellow perch, smallmouth bass and others.  The round goby is native to the Caspian Sea and was discovered in the St. Clair River in 1990 and within 5 years spread to all of the Great Lakes.  It ranges in size up to 7 inches and can be identified by the fusion of its 2 bottom front fins (pelvic) that form a suction cup that allows it to cling to hard surfaces.  The goby is increasing in numbers but it will not completely fill the habitat occupied by smelt and alewife because goby live mainly on the bottom of the lake while smelt and alewife spend much of their time suspended in the mid waters.  The goby is highly successful and there are several traits that enable it to outcompete native species and quickly increase in numbers.  Spawning occurs over a long period from April until September.  It can spawn many times per season and as often as every 20 days.  Females are mature and ready to spawn at age 1 or 2.  The eggs are large, up to ¼ inch in diameter and are deposited in nests that are aggressively guarded by the males.  Several hundred eggs are produced by each female and most eggs successfully hatch.  Goby eat a variety of food including insects, crustaceans, plankton, eggs, fish fry and mussels.  The explosion of zebra and quagga mussels in the Great Lakes has provided the goby with plenty of food.  The goby is specially equipped with pharyngeal teeth in its throat to crush mussel shells and extract the meat.  A goby can eat up to 70 or more mussels per day.  The goby feeds aggressively around rocks and is known to turn them over to find food.  It is very sensitive to movement of its prey and can effectively feed at night providing it with a feeding advantage over many native species.  The goby has been found during the winter as deep as 450 feet in the Great Lakes but during the warmer months it is found in shallow water near shore.  It prefers warmer water and it is not clear if the goby will be available during the summer months to trout and salmon that live in colder water.  The diet study that is occurring this year in Lake Huron will help determine how significant the goby is as a food source for the larger fish.  It is important that anglers participate in the study because knowing what the trout and salmon are eating will allow for better management of the fishery.

Why Attempt to Rehabilitate the Native Cisco?

The cisco is a small whitefish and is also known as herring.  This same species is a popular sport fish in Burt and Mullet Lakes during the winter.  Adults up to 2 pounds are an excellent recreational fish but the younger cisco is a good food source for larger predators such as salmon and trout.  Cisco was the most abundant native fish in the Great Lakes.  It was not only the main food for lake trout but also was the most abundant fish commercially harvested during the early half of the 20^th century.  The Great Lakes populations started collapsing by 1918 and were nearly gone in all lakes by the 1960s.  Currently, the species has rebounded in Lake Superior but in the other Great Lakes only small numbers are present.  In Lake Huron, local populations are found in the Les Cheneaux Island Area, St Marys River, North Channel and parts of Georgian Bay.  Previously, Thunder Bay and Saginaw Bay were the main spawning grounds for cisco.  A successful pilot study was completed this year by the MDNR and other agencies that showed cisco could be raised in Michigan’s hatcheries.  A final review is being conducted to determine the feasibility of stocking cisco in these bays to build up a wild reproducing population on these historic spawning grounds.

Since cisco is a native species and expanding the population could lead to a more abundant and stable food source for all predators including trout, salmon and walleye.  Non-native populations such as smelt and alewife have a tendency to fluctuate greatly since they are not adapted as well to the environment as natives.  Previously, smelt and alewife were present in huge numbers in the mid-waters of Lake Huron where trout and salmon also live.  Smelt and alewife are at record low levels causing a shortage of baitfish.  Cisco also prefers to live in the mid-waters and have the potential of taking the place of smelt and alewife and becoming the dominant food source for trout and salmon. 

Not only could cisco provide more food for larger fish but also it could provide an efficient buffer to protect stocked fish from being consumed quickly after being planted.  There is evidence that when fish are stocked they stand out and are very vulnerable to being eaten by larger fish and birds.  In the past, the planted fish mixed with large numbers of smelt and alewife and few were consumed.  Today there are often low numbers of baitfish present near shore to distract the predators and mortality of the planted fish has been extremely high since 2003.  For example, one 8 pound lake trout caught in Swan Bay this spring had 35 newly planted Chinook in its stomach and a 7 pound lake trout caught during the same trip had 14 Chinook in its stomach.  Increasing cisco numbers might provide more cover by distracting the predators thus increasing overall survival of planted fish.

If anyone has comments, questions or suggestions please contact me.

Frank Krist

Phone: (989) 734-3100 or (989)351-2053

Email krists@speednetllc.com

Native Cisco









Chinook Salmon Harvest Increases in 2008

The results of the Chinook salmon fishery are completed and the harvest at Rogers City was better in 2008 than the year before.  The table below shows the number of Chinook salmon harvested the past two years. 

Northern Lake Huron

Central Lake Huron

Southern Lake Huron

The harvest in Northern Lake Huron has improved while the Chinook fishery south of Alpena remains low.  In addition to the 2008 results in the table above, 1,637 Chinook were caught at Detour and another 1,378 were caught in St. Marys River.  Apparently, the Chinook are adapting to the new food web in the north.  Besides the good Chinook catches, consistent numbers of lake trout and rainbows were caught along with an occasional coho, Atlantic salmon, brown trout and walleye.  The area in Lake Huron from Alpena to Drummond Island is producing an excellent diversified fishery.  Rogers City stands out as the best salmon fishery on Lake Huron.

All the hatchery raised Chinook are marked with a chemical and tests over the past decade indicate that nearly 90% of the salmon recently caught by anglers in the north are wild fish.  It took almost 30 years for the Chinook to become adapted enough to reproduce naturally in large numbers.  Since the dramatic changes in the food web have occurred only since 2003, which I discussed in the last newsletter, the Chinook have had just a short period to adjust to the new food sources.  There is a good chance that the Chinook salmon will continue to increase as each new generation learns to deal with utilizing the changed environment.

Future of Atlantic Salmon in Lake Huron

Atlantic salmon are one of the most famous and prized sport species.  They are long lived since they do not die after spawning and are known for their good size and sporting qualities.  Approximately 20,000 to 30,000 Atlantic salmon have been planted in the St Marys River each year since 1987 by Lake Superior State University.  The Atlantic salmon provide the best return of all planted trout and salmon species stocked in Lake Huron when considering the numbers planted.  The St. Marys River project and a new program in Lake Ontario are the only efforts to establish Atlantics in the Great Lakes.  The State of Maine has a large successful inland program with over 300 lakes containing Atlantic salmon populations and in 176 lakes it is the principal fishery.  The fish have been stocked in Maine since at least 1868 and during the past several decades, much research resulted in producing one of the most successful Atlantic salmon fisheries anywhere.  This new knowledge from Maine and the research conducted by Lake Superior State University in the St Marys River should increase the chances of successfully expanding the fishery in Lake Huron.

Atlantic salmon are actually native to the Great Lakes and were found in very large numbers in Lake Ontario.  They were so common that large numbers were killed with clubs and pitchforks when they entered the rivers to spawn.  The early commercial fisheries easily made large catches with seines along the shores.  The Atlantic salmon were the dominant predator in Lake Ontario and lake trout occupied a minor role.  Niagara Falls prevented the salmon from migrating into the other Great Lakes. 

The region surrounding Lake Ontario was settled by Europeans very early and by 1898 the Atlantics were gone.  It has been speculated that the salmon were eliminated by cutting the forests and converting the land to farmland.  This resulted in much erosion and sedimentation of the spawning streams that smothered the eggs.  Stream flows became erratic and often much of the best spawning areas were without adequate water.  Dams and water pollution caused by the discharge of sewage and contaminants from manufacturing eliminated vast areas of prime spawning habitat.  Finally, the removal of the forests reduced shade along the streams and the water temperatures became too high for the juvenile fish to survive.

The history of Atlantic salmon shows that they could possibly become an important fish in the Great Lakes again.  Michigan experimented with planting Atlantics during the 1970s and 1980s but the program resulted in limited success.  Since that period, much has been learned about culture techniques and life history of the fish.  The Lake Huron Citizens Fishery Advisory Committee is very interested in establishing a pilot study on Lake Huron that might include stocking the fish in one or two new streams and in one or two harbors.  If the plan is successful, potentially the hatchery production could be shifted from the less successful species to Atlantic salmon.

Atlantic salmon could provide a significant recreational fishery because they appear to be better adapted to the food web changes in the Lake and they spend much of their time near shore.  During the spring, they are often caught in shallow water and usually by May and early June the fish return to the planting sites where they are available to anglers for a long period.  The salmon stop feeding around September and spawn in late October and November.  Unlike the Chinook salmon, Atlantic salmon do not die after spawning and return to the Lake.

A Budget Crisis for Fishing and Hunting

Lake Huron’s Fishery and Food Web from 1800s to 2003

In November, I mentioned that I would discuss in this newsletter the changes in the Lake Huron food web and fishery that occurred since the region was settled by Europeans and how these changes are affecting the current fisheries.  In spite of intense exploitation of Lake Huron from modern society, primary production in the food web (algae and zooplankton) has essentially remained stable until just recently.  Changes that have occurred since 2003 have turned the food web upside down.

Lake Huron and the other Great Lakes evolved food webs that efficiently used both the shallow shoal waters and extensive areas of deeper water.  Fish and other organisms could be found from shore to the center of the lake.  Anglers of course, are concerned with high populations of sport fish but a lake’s ability to produce a good fishery depends on the efficient conversion of sunlight to algae which are microscopic plants that are the primary (initial) food source.  To make a vehicle run we add fuel such as gasoline.  In order for a lake to produce life, sunlight is the fuel that must be absorbed and captured.  Lake Huron averages 195 feet in depth with a maximum depth of 750.  Because the water is very clear, sunlight can penetrate over 100 feet enabling the algae to grow to this depth across the entire lake.  Vast amounts of algae absorb energy from the sun and nutrients from the water enabling them to grow.  These algae provide a rich food source for all other organisms including zooplankton, insects and fish.  

The open water above the bottom is known as the pelagic zone.  Small animals called zooplankton live in this mid water zone and feed on the algae.  The zooplankton range in size from approximately 1/64 to 1 inch long and are a major food for small prey fish like smelt which are eaten by the larger predators such as salmon and trout.  The algae that the fish do not consume die and settle to the bottom and are consumed by insects and other small invertebrates.  The two largest zooplankton, Diporeia and Mysis, feed on the bottom like insects do during the day but migrate into the water column at night where they are easily consumed by prey fish.  So by eating the material on the bottom and migrating to the mid waters, Diporeia and Mysis are constantly cycling food that drifted to the bottom back into the pelagic zone.  This was a very efficient system that produced much algae, zooplankton and large numbers of fish.

During the early 1800s the large predators consisted of lake trout, burbot and wallleye.  The smaller prey species were herring (cisco), 6 species of chubs, sculpins and sticklebacks.  The chubs rarely reached lengths greater than 15 inches and were found at all depths including the deeper sections of the Lake.  The chubs lived on or near the bottom.  Only one of the six chub species, the bloater, is still present in the lake.  The herring was the only prey fish that lived suspended above the bottom in the open mid waters (pelagic zone) like the smelt and alewives do today.  Besides providing a stable food source for large numbers of lake trout, the herring could reach a weight of over 2 pounds and was harvested in great numbers by the commercial fishery.

Lake Huron has supported a significant commercial fishery since the about 1860s.  Some gill net effort has been noted as early as 1835 near Alpena and peak production was reached by 1892.  After that, the catch fluctuated but remained high until 1946 when a dramatic decline in the fishery began.  Lake trout, lake whitefish and herring fisheries collapsed in just a few years.  Experts speculate that these fish succumbed to overfishing and the introduction of sea lamprey.  With the demise of these larger more desirable species fishing effort increased for the small deep water chubs which were less vulnerable to sea lamprey attacks.  The introduction of smelt and alewives which appeared to compete with the chubs and heavy fishing pressure brought the collapse to the chub fishery by 1969.  Harvest of all species remained low until about 1980 when lamprey control measures were having a positive impact and the commercial fishery was tightly regulated.   The lake whitefish began to rebound and a sport fishery for salmon and lake trout was established.

Lake Huron’s Fishery and Food Web from 2004 to 2009

From the 1800s when the fish were first exploited in large numbers until about 2004, the species, size and number of the fish changed but the lower food web (algae and plankton) organisms that the fish fed on essentially remained the same.  After 2004, it was becoming clear that profound changes were occurring to the algae and zooplankton communities in Lake Huron.  Similar changes were also occurring in Lakes Michigan, Ontario and Erie.  Research was showing that zebra and quagga mussels were turning the food web upside down.  During the 1990s, these mussels became established in Lake Huron.  Zebra mussels prefer hard bottoms and require water temperature near 50 ⁰F for successful reproduction.  Because of this temperature limitation, zebra mussels are not usually found in water much deeper than 100 feet.  Currently, quagga mussels are replacing the zebra mussels in the Great Lakes including Lake Huron.  Quagga mussels tolerate soft bottoms and cold temperatures so they are found in both shallow and deeper water.  Densities over 10,000 mussels per square meter are common.

Both quagga and zebra mussels are very efficient filter feeders that can strain over a quart of water each day.  Because of their large numbers, the mussels have pulled much of the algae and smaller zooplankton from the water column thus reducing greatly the amount of food in the pelagic zone.  Diporeia, the most desirable zooplankton has nearly disappeared and Mysis the other important large zooplankton is declining significantly, apparently because of the lack of food in the mid waters (pelagic zone).  Instead of the mid waters being productive like they have been for centuries there has been a major shift in food production to the lake bottom.  Most of the available food is tied up in the vast beds of mussels on the bottom with a large reduction in zooplankton.  Since smelt and alewives do not readily feed on the bottom or eat mussels their numbers have greatly declined.  On the other hand, the goby which is a recent invader is a small prey fish that lives on the bottom and eats large quantities of mussels.  The goby is potentially an important food source for larger fish that feed on the lake bottom.  Gobies are found in shallower water during the warmer seasons but have been found in waters over 400 feet deep during the colder months.  The goby is replacing the alewife as an important food fish for some trout and other predators.

It appears that fish species that can adapt to the new food source concentrated on the bottom will do well.  Lake trout are generalists and usually adapt to nearly any food source that is available.  There is evidence that lake trout are feeding heavily on the gobies and are surviving well. 

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