NOTE: This is from the biological report on the status of Atlantic Salmon - see Table of Contents and News Release for additional information.

SECTION 6: DISTRIBUTION AND ABUNDANCE - STATUS OF ATLANTIC SALMON IN THE GULF OF MAINE DPS

6.1 DESCRIPTION OF THE HABITAT WITHIN THE GULF OF MAINE DPS

The Dennys River originates in Lake Meddybemps in the town of Meddybemps, Washington County, Maine. The drainage area of the Dennys River is 34,188 ha, and it flows a distance of 32 km to Cobscook Bay. In addition to Lake Meddybemps, Cathance and Little Cathance Lakes are located in the headwaters of the drainage. The confluence of Cathance Stream, a major tributary, is located approximately 1.0 km upstream from tidewater. The upper reach of the river, from Lake Meddybemps to the falls is flat and slow moving. The reach from the falls to Cathance Stream has flat water stretches and a few riffle areas. The estuary is large, has numerous coves and bays, and numerous peninsulas and islands between Dennysville and the ocean (Beland et al. 1982). Lands within the drainage are sparsely populated and managed for the growth and harvest of forest products and lowbush blueberries. Water quality is generally good, but logging throughout the area has resulted in an abundance of woody debris in some reaches of the river.

The East Machias River originates at Pocomoonshine Lake in the towns of Princeton and Alexander in Washington County, Maine. The river has drainage of 65,009 ha that contains 26 lakes and ponds, and over 50 named tributaries. It flows a distance of 59.5 km to Machias Bay. The watershed is sparsely settled and forested with a mix of spruce and fir. Organic materials from wetlands and bordering lakes and ponds discolor the waters of the river. The East Machias and Machias Rivers enter the same estuary and the lower 3.2 km of the estuary is common to both rivers (Dube and Fletcher 1982).

The Machias River drains an area of over 119,140 ha. It originates from the five Machias Lakes and flows 98 km to Machias Bay. The watershed is located in Washington and Hancock Counties and more than 160 tributaries and 25 lakes and ponds exist in the system. A natural gorge at the mouth of the river in the town of Machias may impede the passage of salmon during periods of extreme high flow. The gorge is being studied by the State of Maine to determine if passage can be improved as part of State rehabilitation efforts for Atlantic salmon in that river. The Machias River headwaters are characterized by rolling hills with forested stream valleys and a number of barren areas, with ground cover typically consisting of shrubs. The lower portion of the basin is composed of large forested areas (Fletcher and Meister 1982). The Machias and East Machias Rivers share a common estuary. The estuary is elongate, approximately 9.6 km in length, but relatively narrow.

The Pleasant River watershed in Washington County originates at Pleasant River Lake in Beddington and drains an area of 22,015 ha. It flows 45 km to the head of tide in the town of Columbia Falls. There are few lakes in the watershed, and the tributaries are a network of small feeder streams with a combined length of 109.4 km (Dube and Jordan 1982). The headwaters are composed mostly of hills and ridges, with forests of spruce, fir, and hardwoods. The river water exhibits a high degree of red-brown coloration caused by leaching of roots, leaves, and other organic materials that originate from extensive peat bogs in the drainage. The bogs provide water during dry periods, storage during wet periods, and moderate discharge in the basin (Dube and Jordan 1982). The Narraguagus River originates at Eagle Lake, flows through Washington and Hancock Counties, and drains an area of approximately 60,088 ha. The main stem drops a total of 124 m over a distance of 69 km to the head of tide in Cherryfield. The West Branch of the Narraguagus, a major tributary, has a drainage area of approximately 18,100 ha and reaches the main stem 3.2 km upstream from the head of tide. There are more than 402 km of streams and rivers in the drainage and about 30 lakes and ponds, with three of the lakes exceeding 162 ha in size (Baum and Jordan 1982). The topography of the headwaters consists of rocky hills and ridges, and forests that are primarily a mix of spruce and fir interspersed with hardwoods. There are large blueberry barrens in the watershed, and lands are primarily managed for berry production and forest products.

The Ducktrap River is relatively small compared to other Atlantic salmon rivers in Maine. It originates in Tilden Pond in Belmont Township, Waldo County, has a drainage area of approximately 9,324 ha, and flows for a distance of 10.7 km to Lincolnville where it enters Penobscot Bay. There are four ponds in the drainage and two major tributaries. The two tributaries, Kendall and Black Brooks, enter the main stem in the lower portion of the drainage. The surrounding area is sparsely settled, and former agricultural lands are either overgrown or reverting to early successional growth. The drainage is rugged and hilly, and in the lower portion the riverbanks rise sharply from the stream to heights that exceed 30.5 m (Bryant 1956).

The Sheepscot River originates as a series of hillside springs in West Montville, Waldo County and flows a distance of 54.7 km to the estuary near Alna. The West Branch of the river originates at Branch Pond in Kennebec County, flows a distance of 24 km and enters the main stem in Sheepscot. The Dyer River, the largest of the tributaries, has a length of 27.3 km and flows to the estuary. The Sheepscot River drainage includes 24 lakes and ponds and encompasses an area of 59,052 ha. The upper portion of the Sheepscot River estuary resembles a fjord, whereas the lower portion is typical of Gulf of Maine DPS watersheds, with mud flats and salt marsh covering large areas. Sheepscot Falls, located in the upper estuary, is an area composed of ledge, and the site of a former dam (Meister 1982). Land within the watershed was once intensively farmed, but the majority is now forested. Deposited glacial material provides a source of boulder, rubble, and cobble in the drainage.

6.2 SURVEYS OF AVAILABLE FRESHWATER PRODUCTION HABITAT WITHIN THE GULF OF MAINE DPS

The ASA and FWS are presently conducting more thorough habitat surveys of Cove Brook and other smaller coastal drainages to better quantify available habitat in those drainages (Buckley, FWS, pers. Comm.). Additionally, the FWS Gulf of Maine Project is currently undertaking a study on the Narraguagus River to use airborne infrared imagery to identify cool water refugia for Atlantic salmon. A spatially continuous temperature profile can be obtained for the river using this technology. One objective is to determine if cold water inputs are predictable on an annual basis regardless of stream flow and water temperature. The imagery is currently being processed so it is too early to state whether this technology will be useful in the future in the Narraguagus River and other rivers within the DPS (Wright 1998).

Figure 6.2-1: Dennys River Watershed
Figure 6.2-2: East Machias River Watershed
Figure 6.2-3: Machias River Watershed
Figure 6.2-4: Pleasant River Watershed
Figure 6.2-5: Narraguagus River Watershed
Figure 6.2-6: Ducktrap River Watershed
Figure 6.2-7: Sheepscot River Watershed

6.3 DESCRIPTION OF POPULATION ABUNDANCE WITHIN THE GULF OF MAINE DPS

6.3.1 ADULT ABUNDANCE

For an individual river, most past counts of returning adult wild salmon are of limited value in assessing the population trends because of the inconsistent methods and discontinuous nature of gathering adult return counting data. The exception is the Narraguagus River, where adult counting effort and technique have been relatively consistent over recent years (Beland and Dubé 1999). The Narraguagus River adult return data are useful for showing that these wild populations have been low this past decade relative to observations of earlier decades and reasonable expectations of habitat carrying capacity. Given the limitations described, absolute values of adult estimates in a single year cannot be used to assess the immediate condition of a stock in a river or to determine if listing is warranted. However, when individual river data are combined in aggregate they provide a relatively robust indication of population trends within the Gulf of Maine DPS. The development of fixed weirs and other improvements in population assessment included in the Atlantic Salmon Conservation Plan for Seven Maine Rivers will, by the year 2001, upgrade the effectiveness of monitoring adult returns to more accurately index the true state of the wild populations. This will also permit a more precise evaluation of short-term fluctuations in a population. It is important that this increased precision be achieved by that time, because 2001 is when the first significant impact of fry stocking on adult returns should be realized in the Gulf of Maine DPS.

Atlantic salmon documented to have returned to rivers within the DPS through angler catch and trap data from 1970 to 1998 provide the best available composite index of recent adult population trends (Table 6.3.1-1; Figure 6.3.1-1). These indices indicate that there was a dramatic decline in the mid-1980s and populations have remained at low levels since that point.

Figure 6.3.1-1 and Table 6.3.1-1: Total Documented Natural (Wild & Fry Stocked) Spawner Returns from USASAC (1999) data (minimal* indices) and escapement goal (e-goal) for each river in the Gulf of Maine DPS.

With 100,000 m² of accessible habitat, target spawners would be:

100,000m² X 2.4 eggs/m² = 240,000 eggs;

240,000 eggs / 7,200 eggs/female = 33.333 females; and

33.333 x 2 = 66.67 = 67 Atlantic salmon

An escapement goal of 67 spawners and index of 35 spawners:

(35/67) x 100 = 52.23% of escapement goal

The pre-fishery abundance index of North American salmon stocks that migrate to the Greenland region of the North Atlantic Ocean continues to be low in spite of apparently improving marine habitat conditions as reflected by ocean surface temperature data in the past few years (NASWG 1999). The apparent non-response to improving marine habitat is believed to be due, in part, to generally depressed spawning populations in North American home rivers and resultant low number of juvenile salmon entering the ocean. Without adequate numbers of emigrating smolts, North American populations have not responded to improved marine growth and survival conditions. Based on estimates of the pre-fishery abundance of North American salmon stocks in the West Greenland Sea provided by the ICES, relatively low adult returns should be anticipated in many North American salmon rivers again in 1999 (NASWG 1999).

Fall redd counts are also used to estimate adult returns. These counts are particularly useful for rivers that do not have trapping facilities for returning adults. The accuracy of the counts of redds created by spawning adults varies due to water conditions (visibility, discharge, water temperature, etc.) and the amount of observation effort (Beland and Dubé 1999). Low, clear water conditions in the fall can provide a high level of efficiency in counting redds by both enhancing river accessibility for observers and the visibility of redds; while high, turbid water limits access and visibility and greatly lowers counting efficiency. Such sampling conditions can vary day-to-day and river-to-river. The value of the past redd counts for assessing the wild populations lies more in the trends of changes in their relative values over a period of years, and less in their absolute values of particular years or rivers. Recent increases in redd counts can be attributed to increased coverage of watershed and supplemental broodstock releases (Table 6.3.1-3; Figure 6.3.1-3). Those releases will be discussed later in this section under the heading of stock enhancement programs.

Declining adult Atlantic salmon returns of the last three decades are best characterized by an early period of relatively high fishing mortality that has declined to minor levels while marine habitat suitability declined severely. As marine habitat indices improved in the early 1990's, the ability of the stocks to respond has been hindered by low spawner abundance caused by previous marine mortality factors. The ability and resilience of Atlantic salmon stocks to return to high abundance is strongly related to the abundance of spawners (i.e., Myers and Barrowman 1996). Since 1970, there has not been a substantial period of time where: marine habitat indices were high; fishing mortality was low; and spawner abundance was at conservation targets for any Atlantic salmon stocks in the Gulf of Maine DPS.

Figure 6.3.1-3 and Table 6.3.1-3

6.3.2 Juvenile Abundance

A total parr population estimate is not available for the entire DPS; however, the ASA and NMFS have conducted a drainage-wide parr population study on the Narraguagus River since 1991. Electrofishing population estimates at select index sites are extrapolated to a basinwide estimate using a habitat based stratification design (Beland and Dubé 1999). The numbers presented in the table below are obtained by electrofishing up to 45 sites annually. The parr population in the Narraguagus River has increased in recent years. This increase is most likely attributed to the river-specific stocking program including both fry stocking and adult broodstock releases (Beland and Dubé 1999).

The 1997 parr population estimate in the Narraguagus River was the highest estimate in the time series of data. In 1997, the basin-wide population estimate of large parr in the Narraguagus was 26,682, an increase of 113% from the 1996 estimate (Beland and Dubé 1999). The drainage-wide population of age 1+ and older parr on the Narraguagus River in 1998 was approximately 25,382, a 5% decrease from the 1997 high (USASAC 1999).

6.3.3 Smolt Production and Outmigration

In addition to using traps to estimate total smolt production in the Narraguagus River, researchers implanted ultrasonic pingers into wild smolts and hatchery smolts to investigate their behavior and fate as they moved downriver and into the estuary in 1997 and 1998 (Kocik et al. 1998). Preliminary data on detection percentages between transects averaged 90% in the riverine section, 91% in the estuary, and dropped to 83% at the marine array, suggesting a zone of increased mortality in Narraguagus Bay. The median transit time for wild smolts from the first detection unit to the marine array (21 km) was 84 hours, yielding a median speed of 0.3 km/h, slower than the speed observed in 1997 (0.5 km/h). Slower outmigration in 1998 may be due to lower stream flows and warmer temperatures (Kocik et al. 1998b). Preliminary estimates of survival indicate that roughly 50% of smolts are presently emigrating from the outer waters of Narraguagus Bay and entering the Gulf of Maine.

NMFS and ASA researchers illustrated that between the 1997 and 1998 smolt runs, a 126% increase in large parr production resulted in less than a 2% increase in smolt production. Additionally, these researchers found that approximately half of these emigrating smolts do not reach the Gulf of Maine. These preliminary data led the BRT to conclude that low overwinter and emigration survival rates may be impeding the recovery of these populations and are an issue of concern.

6.4 Conservation Hatchery Programs

The focus of the river specific program is to produce fry that are then stocked back to the river of their parent's origin. In 1992, fry stocking began with the release of less than 14,000 fry in the Machias River. It was only in 1997 that stocking reached levels where most of the suitable and unutilized habitat is fully stocked at a target density of 100 fry per habitat unit (100 m²) in the five target rivers (Copeland1998). Egg take and subsequent fry stocking has increased significantly as broodstock numbers increased at CBNFH (Copeland 1998)(Table 6.4-2). Fry stocking occurs in May after most or all of the yolk sac has been absorbed and the fish are ready to begin actively feeding (Copeland et al. 1998). Each year the ASA makes a recommendation to the TAC regarding fry stocking. The TAC then reviews the recommendation and forwards a final recommendation to the ASA, USFWS and NMFS. In 1999, ASA staff provided the TAC with a detailed rationale for their fry stocking recommendations. Primary considerations for selecting river reaches for fry stocking include habitat quality, avoiding direct competition between stocked fry and emerging wild fry, and finally, logistics (ASA Rationale for Fry Stocking Recommendation, ASA staff, 2/1/99). River specific fry releases are displayed in the table below (Table 6.4-3). Parr were collected from the Pleasant River but were not stocked later back into the Pleasant River due to the presence of a disease. This will be discussed later in Section 7.3.

The response of Atlantic salmon populations to supplemental stocking programs can be partially evaluated based on juvenile production but adult returns are the ultimate evaluation stage. It takes about 4 years from initial stocking to evaluate population level responses since there is a lag between removal of parr for brood stock development, the subsequent stocking of their offspring, juvenile assessments, and adult returns. The first opportunities to make a comprehensive evaluation will be when adults of fry-stocked origin (as 2 SW fish) potentially contribute to the 1999 spawning run that ends in October. The 1999 returns are from the moderately high fry stocking levels of 1995 for the Dennys, Machias, and Narraguagus Rivers. It will not be until 2000 that fry-stocked fish will contribute a potentially substantial element to all five rivers with river specific stocking programs in them.

*provisional data

Due to space constraints, there is a need to annually remove a portion of the broodstock held at CBNFH. These fish were spawned the previous year in the hatchery and are released prior to the spawning season. Experimentation on the Narraguagus River has verified that these fish do spawn after being released to the wild and that the fry survive to the parr stage. Broodstock for recent releases are provided in the table below.

Table 6.4-4: River specific surplus broodstock releases (Copeland et al. 1998)

During the development of the Conservation Plan, the Governor's Task Force voted to transfer eggs from the CBNFH to private hatcheries operated by commercial growers. The transfer was made after the aquaculture industry offered to assist in the recovery of the DPS by raising smolts and/or adults as a supplement to fry releases. A total of 3,000 eggs from three strains were transferred from the CBNFH to the aquaculture industry in 1996, 1997, and 1998. Smolts of the following strains were placed into sea cages in the spring of 1999: Narraguagus River, Machias River, Dennys River and Sheepscot River. Not all of these smolts will be moved to cages, as the adults produced would be far in excess of what would be biologically appropriate for use in the river. The additional smolts could be released in the river. Most hatcheries produce smolts in one year, but within a year class or cohort many fish remain as parr and smoltify in the second year. Thus, parr are a "by-product" of smolt production and are available for stocking into the river. To date, age 0+ fall parr were stocked into the Narraguagus, Machias, Dennys, and Sheepscot Rivers.

Five river-specific stocks (Narraguagus, Machias, East Machias, Dennys and Sheepscot) are currently being reared in sea cages and 2SW adults will be available the next two years. Estimated production of adult fish will be 900 for the Narraguagus (available in 1999); and 1,800 each for the Machias, East Machias, and Dennys Rivers (available in 2000). These numbers are far in excess of any realistic biological needs that would be prudent for experimental release of adults into their rivers of origin. Their numbers are excessive because it is necessary to produce fish at these levels to acclimate them to feed in the sea cages, to make optimal use of cage rearing space, and as insurance against catastrophic losses (e.g. loss of 1,000 Narraguagus River fish last winter to seal predation). The NMFS, USFWS and ASA will tag these fish so that release options can be evaluated. The TAC has advised that the release of adults in rivers with limited adult assessment capabilities should be restricted since little is known of impacts (positive or negative) upon ongoing restoration efforts.

6.5 Determination of Population Status

Adult counts and redd counts in all rivers continue to show a downward trend from these low abundance levels. Given recent estimates of spawner-recruitment dynamics some researchers suggest that adult populations may not be able to replace themselves and populations would be expected to decline further (Beland and Friedland 1997). Preliminary evaluations indicate that fry stocking is enhancing juvenile production in these rivers and utilization of available nursery habitat has increased. While hatchery supplementation is an important demographic and genetic conservation tool for these stocks, the evaluation of the status of these populations need to be based on the population trends of wild stocks. Because the present hatchery program utilizes primarily fry stocking and no effective non-lethal fry mark has been developed, the BRT could not assess only the wild component of juvenile or adult populations. However, given that the overall status of these stocks is so poor that the BRT concludes that the wild element of combined natural (wild and fry stocked) Atlantic salmon presmolts are at precariously low levels of abundance. Additionally, data from Kocik et al. (1998a) suggest that presmolt overwinter mortality may be substantially greater than values used in previous population modeling exercises (Beland and Friedland 1997). Given this information, the BRT concludes that the abundance of naturally produced Atlantic salmon in the Gulf of Maine DPS is continuing the downward trend in abundance that began in the late 1980's and is characteristic of the entire North American stock complex (NASWG 1999; USASAC 1999).

The demographic and genetic consequences of these low abundance levels coupled with declining abundance trends leads the BRT to conclude that the conservation status of the population segment in relation to ESA listing standards is in danger of extinction.