4 North American commission
4.8 Comparison with previous assessment and advice
4.9.7 Elaboration on status of stocks
To date, 728 Atlantic salmon rivers have been identified in eastern Canada (DFO and MNRF 2008) and 21 rivers in eastern USA, where salmon are or were present within the last half century. The upward revision to that previously reported by ICES (2008) is attributable to a number of factors where, especially in Labrador, recent informa‐
tion on the presence of salmon has changed. Assessments were reported for 73 of these rivers in 2008.
4.9.7.1 Smolt and juvenile abundance
Canada
Wild smolt production was estimated in 14 rivers in 2008. Of these, ten rivers have at least ten years of information (Figure 4.9.7.1.1).
In 2008, smolt production increased (>10% change) from 2007 in two rivers, decreased in seven rivers and remained unchanged in five rivers (Figure 4.9.7.1.1). The relative smolt production, scaled to the size of the river using the conservation egg require‐
tia Fundy and the USA river. In the ten rivers monitored over at least the past ten years, there has generally been no significant linear change in smolt production (P>0.05) with the exception of significant decreases in Narraguagus (US) and Trinité (Québec) and significant increases in Rocky and WAB (Newfoundland).
Juvenile salmon abundance has been monitored annually since 1971 in the Miramichi (SFA 16) and Restigouche (SFA 15) rivers and for shorter and variable time periods in a large number of other rivers in the Maritime Provinces. In the rivers of the southern Gulf of St. Lawrence, densities of young‐of‐the‐year (age 0+) and parr (age 1+ and 2+) have increased since 1985 and densities of fry and parr in 2008 remained at high val‐
ues. Rivers in SFAs 20 and 21 along the Atlantic coast of Nova Scotia are high in dis‐
solved organics, have low productivity, and influenced by acid deposition. In the partially acidified St. Mary’s River, fry and older parr densities remained among the lowest of record (1985–2008). Trends in densities of age 1+ and older parr in the outer Bay of Fundy (SFA 23) have varied since 1980, with densities in the Nashwaak River and Saint John River above Mactaquac Dam declining in response to reduced spawn‐
ing escapements.
A region‐wide electrofishing survey was conducted along the Atlantic coast of Nova Scotia in 2008 and compared to a survey in 2000. These surveys were similar in terms of total effort and coverage, although marginally more sites were completed in 2008 (143 vs. 128), but one less river was visited (51 rather than 52). Just under one third as many juvenile salmon were captured in 2008 (977 salmon) than in 2000 (3046 salmon).
In 2000, juvenile Atlantic salmon were found in 54% of the rivers (28 of 52), but were only found in 39% (20 of 51) of the rivers in 2008. Where present in 2008, the observed densities of juvenile salmon from all year classes ranged from 0.3 to 33.9 fish per 100
m2 (Figure 4.9.7.1.2). These densities were very low compared to densities of parr in
the Gulf Region and other areas. Overall, the mean density of age 0 juveniles de‐
creased from 5.0 to 1.9 fish per 100 m2 between 2000 and 2008, while the mean density of age 1 and older parr decreased from 3.5 to 0.9 fish per 100 m2. In six rivers in 2008, only one life stage was found (either fry or parr), but it is possible that additional ef‐
fort or alternate site selection would have resulted in the capture of the other in the system. Of the sites surveyed in both years (n = 74), total juvenile density decreased in 43% (n = 32) and increased in 8% (n = 6). The remainder of the sites (n = 36) had densities of zero in both years. In addition, juvenile salmon were not found at 7 sites and 2 rivers in 2008 where they were found in 2000.
USA
Wild salmon smolt production has been estimated on the Narraguagus River for twelve years (Figure 4.9.7.1.1). Smolt production in 2008 was 17% below that of 2007 with a significantly (P < 0.05) decreasing trend since 1998. The estimated juvenile population in this river has also declined over the period.
4.9.7.2 Estimates of total adult abundance by geographic area
Returns of small (1SW), large, and 2SW salmon (a subset of large) to each region (Ta‐
bles 4.9.7.2.1, 4.9.7.2.2 and 4.9.7.2.3; Figures 4.9.7.2.1, 4.9.7.2.2 and 4.9.7.2.3; and Annex 5) were originally estimated by the methods and variables developed by Rago et al., 1993b and reported in ICES, 1993. However, at the 2009 Working Group meeting there were some changes to the input variables and techniques used especially in the case of Labrador. The returns for individual river systems and management areas for both sea‐age groups were derived from variety of methods. These methods included counts of salmon at monitoring facilities, population estimates from mark-recapture
166 | ICES WGNAS REPORT 2009
rates, and measurements of freshwater habitat. The 2SW component of the MSW re‐
turns was determined using the sea-age composition of one or more indicator stocks.
In Labrador, for the years, 1998–2001 there was no data available with which to esti‐
mate returns and spawners because the commercial fishery had closed and there were only one or two counting projects. Consequently, previous analyses for Labra‐
dor used raising factors estimated based on the proportion that Labrador small and 2SW salmon were to the total PFA during the years when Labrador estimates were available (Reddin, 1999). These factors (1.04 to 1.49 for small salmon and 1.05 to 1.27 for large salmon) were multiplied by the PFA in 1998–2001 to provide values for re‐
turns and spawners to Labrador. At the 2009 Working Group meeting, it was decided to re‐examine the Labrador data to find a new method of determining returns and spawners for the 1998–2001 period that utilized data from Labrador rather than PFA as was described above. The basis for estimates of 2SW and 1SW salmon returns and spawners for Labrador (SFAs 1, 2 and 14B) prior to 1998 are catch data from angling and commercial fisheries. In 1998, the commercial fishery in Labrador was closed and the model for returns and spawners from commercial catch data could not be used.
From 2002–2008, there were counting projects on four salmon rivers in Labrador. Be‐
cause the same four out of about 100 rivers (one in SFA 1A, Northern Labrador and three in SFA 2) were monitored, the Working Group extrapolated from return rates per accessible drainage areas to the un‐surveyed rivers in Labrador (ICES 2005). In order to provide new estimates of returns and spawners for Labrador for 1998–2001 two dataseries were examined one being angling catch data and the other the FSC landings. Since there were no FSC landings in 1998 and because of a perceived effect on landings of increasing effort in FSC fisheries in 1999–2001 compared to 2002 to present it was decided to use the angling data. The return estimates of small, large, and 2SW salmon for 2002 to 2008 were used to determine exploitation rates based on small retained fish and large retained and hooked‐and‐released in the angling fish‐
ery. The average of these exploitation rates for the years 2002–2008 were then applied to the angling catches in 1998–2001 to provide new estimates returns in those years.
The spawners for Labrador were derived by subtracting the angling catches from the returns.
Returns are the number of salmon that returned to the geographic region, including fish caught by homewater commercial fisheries, except in the case of the Newfound‐
land and Labrador regions where returns do not include landings in commercial and food fisheries. This avoided double counting fish because commercial catches in Newfoundland and Labrador and food fisheries in Labrador were added to returns to create the PFA of North American salmon.
Total returns of salmon to USA rivers are the sum of trap catches and redd based es‐
timates. Returns do not include aquaculture escapes in rivers where removal is possi‐
ble. In the Magaguadavic River (SFA 23) 6 fish farm escapees were removed in 2008.
A single aquaculture escapee was also intercepted on the St. Croix River.
Canada Labrador
The mid-point of the estimated returns (201 069) of small salmon to Labrador rivers in 2008 is 5% higher than in 2007 and 26% above the previous five year mean return (Figure 4.9.7.2.1). The mid-point (17 785) of the estimated 2SW returns to Labrador rivers in 2008 was 19% higher than in 2007 and 38% higher than the recent 5‐year av‐
Newfoundland
The mid-point of the estimated returns (248 970) of small salmon to Newfoundland rivers in 2008 is 36% higher than in 2007 and 16% higher than the average small re‐
turns (214 103) for the past five years (Figure 4.9.7.2.1). The mid-point (4009) of the estimated 2SW returns to Newfoundland rivers in 2008 was 4% lower than in 2007 and 3% lower than the recent 5-year average of 4129 (Figure 4.9.7.2.3).
Québec
The mid-point of the estimated returns to Québec in 2008 of small salmon (36 017) is 59% above that estimated in 2007 and 27% above the previous five-year mean (Figure 4.9.7.2.1). The mid-point of the estimated returns of 2SW (29 123) salmon is 22%
above that estimated for 2007 and 3% above the previous 5-year average (Figure 4.9.7.2.3).
Gulf of St. Lawrence, SFAs 15−18
The mid-point (52 209) of the estimated returns in 2008 of small salmon to the Gulf of St. Lawrence was 55% higher than 2007 and 10% above the previous five year mean return (Figure 4.4.7.2.1). The mid-point (177 340) of the estimate of 2SW returns in 2008 is 19% lower than for 2007 and 22% below the previous 5-year average return (Figure 4.9.7.2.3).
Scotia-Fundy, SFAs 19–23
The mid-point (15 344) of the estimated returns in 2008 of small salmon to Scotia‐
Fundy 99% higher than 2007, a 94% increase over the previous five year mean return, but low relative to the 1971–2007 time‐series (Figure 4.9.7.2.1). The mid-point (3041) of the estimate of 2SW returns in 2008 is 121% higher than 2007 and 32% above the previous 5-year average return (Figure 4.9.7.2.3).
The model presently being used to extrapolate from the Nova Scotia Atlantic coast assessed rivers to total abundance (both returns and spawners) within the region is likely leading to an overestimation of current regional abundance. The model is based on the assumption that the LaHave River salmon count is a representative in‐
dex of overall Scotia‐Fundy abundance, an assumption that is likely invalid (see Sec‐
tion 4.9.7.1). The estimated range of MSW spawners produced by this model is 1912 to 2634 salmon, whereas counts of salmon in five rivers thought to contain a high (but unknown) proportion of the MSW spawners total 869. The bias on the estimate of 1SW spawners is likely greater. Because the model estimates are well below the re‐
gional conservation requirement and represent only a small fraction of the total abundance of salmon in North America, this issue is expected to have very little effect on the advice provided on overall status of salmon in North America, but does have implications for regional management.
USA
The returns in 2008 of 1SW (814) was 174% higher than 2007 and 151% above the pre‐
vious five year mean return (Figure 4.9.7.2.1). The returns of 2SW (1764) was 85%
higher than 2007 and 62% above the previous 5‐year average return (Figure 4.9.7.2.3).
Total return of salmon to USA rivers was 2613, a 108% increase from returns in 2007 (1255) and 24% above the long term average (1967–2007).
4.9.7.3 Estimates of spawning escapements
168 | ICES WGNAS REPORT 2009
are provided in Table 4.9.7.3.3 and a comparison between the numbers of spawners, returns, and CLs for 2SW salmon in presented in Figure 4.9.7.2.1 and a comparison between the numbers of spawners and returns small salmon is presented in Figure 4.9.7.2.3.
Canada Labrador
Spawner estimates for Labrador in 1998–2008 were developed, using the monitoring facilities for 2002–2008 and the new method based on angling exploitation rates for 1998–2001 (Section 4.9.7.2). The mid-point of the estimated numbers of 2SW spawners (17 559) was 38% above the previous year and was 50% of the total 2SW CL for Lab‐
rador (Figure 4.9.7.2.3). The 2SW spawner limit has only been exceeded once (1998) since 1971. The mid-point of the estimated numbers of small spawners (198 916) was 5% higher that estimated for 2007 (Figure 4.9.7.2.1).
Newfoundland
The mid-point of the estimated numbers of 2SW spawners (3945) in 2008 was 4% be‐
low that estimated in 2007 (4102) and was 98% of the total 2SW CL for all rivers. The 2SW CL has been met or exceeded in five years out of the last ten (Figure 4.9.7.2.3).
The small spawner abundance (225 163) in 2008 was 26% higher than in 2007 (167 691, Figure 4.9.7.2.1). There was a general increase in both 2SW and 1SW spawners during the period 1992–96 and 1998–2000, which is consistent with the closure of the com‐
mercial fisheries in Newfoundland.
Québec
The mid-point of the estimated numbers of 2SW spawners (22 453) in 2008 was 30%
above 2007, 10% above the previous five year mean, and was about 74% of the sum of the 2SW CL for all rivers (Figure 4.9.7.2.3). The mid-point of the estimated small spawner abundance in 2008 (25 447) was 34% above the value in 2007 (Figure 4.9.7.2.1) and 24% above the previous five-year average.
Gulf of St. Lawrence, SFAs 15−18
The mid-point of the estimated numbers of 2SW spawners in 2008 was 19% below 2007, and 23% below the previous five year mean, and was about 56% of the sum of the 2SW CL for all rivers (Figure 4.9.7.2.3). The mid-point of the estimated small spawner abundance in 2008 (37 740) was 32% above 2007 (Figure 4.9.7.2.1).
Scotia-Fundy, SFAs 19–23
Estimated numbers of 2SW spawning salmon in the Scotia Fundy area was about 2960 fish which was 55% higher than the previous five year mean, a 131% increase from 2007 and 12% of the 2SW CL for all rivers (Figure 4.9.7.2.3). Estimated small spawners was about 15 100, a 96% increase from the previous five year mean and a 50% increase from 2007 (Figure 4.9.7.2.1). As was the case with returns, these values may be overestimates.
USA
Pre‐spawning adults were stocked into USA rivers, however, even with these, all age classes of spawners (1SW, 2SW, 3SW, and repeat) in 2008 (3045 salmon) represented only 10% of the 2SW spawner requirements for all USA rivers combined (Figure
4.9.7.4 Reconstructed spawning escapements
Lagged spawner estimates for each of the six geographic areas and overall for North America were derived using Monte Carlo simulations following the technique out‐
lined in ICES (2005). Spawners in each geographic area were allocated (weighted forward) to the year of the non‐maturing 1SW component in the Northwest Atlantic using the weighted smolt age proportions from each area (Table 4.9.7.4.1). The origi‐
nal USA smolt age distributions are used to allocate the USA spawners for years 1971–1989 and the new distribution for 1990 onward. The total spawners for a given recruitment year in each area is the sum of the lagged spawners. Because the smolt age distributions in North America range from one to six years and the time‐series of estimated 2SW spawners to North America begins in 1971, the first recruiting year for which the total spawning stock size can be estimated is 1979 (although a value for 1978 was obtained by leaving out the 6‐year old smolt contribution which represents 4% of the Labrador stock complex).
Spawning escapement of 2SW salmon to several stock complexes has been consis‐
tently below the 2SW CLs (Labrador, Scotia‐Fundy, USA) over the entire time‐series (Figure 4.9.7.4.1). The only regions to have frequently met or exceeded their CLs are Newfoundland and Gulf. Spawners have declined to less than the CLs for Quebec since 1991 and for Gulf since 1996. Regionally, the trends in lagged 2SW spawner abundance over the past ten years have been variable: decreased in Scotia‐Fundy, no trend in USA and Quebec, highly variable abundance in Gulf, Newfoundland and Labrador. Overall for NAC, lagged spawners have declined from peak abundances of over 100 000 spawners in the late 1970s to just over 60 000 spawner equivalents over the past ten years.
The relative contributions of the stocks from these six geographic areas to the total spawning escapement of 2SW salmon has varied over time. The reduced potential contribution of Scotia‐Fundy stocks and the increased proportion of the spawning stock from Labrador and Newfoundland to future recruitment are most noticeable.