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

SECTION 8: CONCLUSION

As discussed both in the 1995 Status Review and this review, dams and overfishing are major factors contributing to the past precipitous decline of Atlantic salmon that resulted in its current low abundance. The analysis of the listing factors in 1999 clearly indicates that all threats to the species have not been removed and identify the existence of threats from disease and freshwater production. There is currently no clearly identifiable cause for the critically low abundance of Atlantic salmon in the Gulf of Maine DPS. A single threat cannot be identified as the factor for the current state of the DPS; the focus is more properly placed on the cumulative effect of the multiple threats identified. At current levels of abundance, it is difficult to discuss any threat to the species and its habitat as negligible.

Under the first listing factor, present or threatened destruction, modification, or curtailment of habitat or range, the following threats to Atlantic salmon habitat within the DPS watersheds were identified: (1) water extraction; (2) sedimentation; (3) obstructions to passage caused by beaver and debris dams, poorly designed road crossings, and dams; (4) input of nutrients; (5) chronic exposure to insecticides, herbicides, fungicides, and pesticides (in particular, those used to control spruce budworm); (6) elevated water temperatures from processing water discharges; and (7) removal of vegetation along streambanks.

Efforts are underway to better understand and balance the needs of Atlantic salmon and the water use needs of the agriculture industry. Until this process is completed, the threat of excessive or unregulated withdrawal remains. Chronic exposure to chemical residues in the water negatively affects Atlantic salmon and since these chemicals have been used within the Gulf of Maine DPS, there is a substantial threat from these chemicals. Sedimentation from a variety of sources also warrants closer review as it may alter habitat and render it incapable of supporting maximum Atlantic salmon production. Recent studies indicate that full freshwater production potential is not being achieved despite fry stocking efforts. These results suggest that a factor or factors within the rivers may be negatively impacting freshwater habitat for Atlantic salmon. Although it is difficult to isolate and evaluate the impact of individual habitat issues, the available information indicates that cumulative impacts from habitat degradation issues discussed above pose a significant threat to Atlantic salmon stocks.

Historically, under the second listing factor, both commercial and recreational harvest of Atlantic salmon played an important role in the decline of the DPS of Atlantic salmon. Continuation of the internal use fishery in Greenland poses a reduced but continuing threat to Atlantic salmon in the DPS. Continuation of the existing directed catch and release fishery may cause mortality or injury to Atlantic salmon within the DPS. Recreational fisheries targeting other species also may incidentally catch various life stages of Atlantic salmon sometimes resulting in their injury or death. Mortality from fishing increases the threat to Atlantic salmon survival.

The impact of predation and disease was examined under the third listing factor and was found to have increased since the 1995 Status Review. Predation has always been a factor influencing salmon numbers, but under conditions of a healthy population, would not be expected to threaten the continued existence of that population. The threat of predation to the DPS is significant today because of the very low numbers of adults returning to spawn and the dramatic increases in population levels of some predators known to prey on salmon. These include cormorants, sea birds, striped bass, and several species of seals.

Fish diseases have always represented a source of mortality to Atlantic salmon in the wild, though the threats of major loss due to disease are generally associated with salmon culture. Three recent events, occurring during the last three years, have increased the concern for disease as a threat to the DPS: (1) the appearance of ISA virus in 1996 on the North American continent within the range of the possible exposure of migrant DPS salmon; (2) the discovery in 1998 of the retrovirus SSSV within a DPS population; and (3) the new information available in 1999 on the potential impact of cold water disease on salmon. The nature of these three specific developments in terms of direct loss to the DPS from disease in the wild is extremely difficult to assess. Observations to date suggest that direct mortality may not be the major threat to the DPS from these diseases. However, there is an indirect threat through the impact of these diseases on the river-specific fish culture program implemented on six rivers to enhance maintenance and recovery of these imperiled populations. The impacts of ISA, SSSV, and CWD appear to be magnified when fish are held in culture environments. Diseases significantly degrade the effectiveness of fish culture techniques as a recovery tool and strategy for stock enhancement. The level of threat to the perpetuation and recovery of the DPS from salmon disease has significantly increased in the past three years.

Under the fourth listing factor, the BRT examined regulatory mechanisms for their ability to protect the Gulf of Maine DPS. A variety of state and federal environmental statutes and regulations are in place to address potential threats to Atlantic salmon and their habitat. These laws are complemented by international actions under NASCO and many interagency agreements and state-federal cooperative efforts. Implementation and enforcement of these laws and regulations must be strengthened to further protect Atlantic salmon. The appropriate state and federal agencies have established coordination mechanisms and have joined with private industries and landowners in partnerships for the protection of Atlantic salmon. These partnerships will be critical to the recovery of the species. As explained in Section 7.4, existing regulatory mechanisms have not removed all of the threats to wild Atlantic salmon.

Aquaculture practices were examined under the fifth listing factor, other natural or manmade factors affecting the continued existence of the DPS. Farm-raised or aquaculture Atlantic salmon escape during freshwater rearing, transport, or sea cage growout and enter rivers within the Gulf of Maine DPS. Available genetic data and visual observations indicate that aquaculture escapees may have successfully interbred with wild Atlantic salmon in the DPS. Under current aquaculture practices, this problem will persist because the escape of aquaculture salmon, and their interactions with wild stocks, is expected to increase with the continued growth of the aquaculture industry in the State of Maine. Escaped aquaculture salmon have been documented to disrupt redds of wild salmon, compete with wild salmon for food and habitat, interbreed with wild salmon, and transfer disease or parasites to wild salmon. This is of grave concern, particularly when the escapees are not of North American origin. The expanding use of reproductively viable European stock by the aquaculture industry has greatly increased the level of risk of negative consequences from introgression of aquaculture stock into wild populations. Scientific information indicates that interactions between wild and aquaculture salmon in the DPS may lead to decreased numbers of wild Atlantic salmon, and in the extreme, to extirpation of the wild stock. Comprehensive protective solutions to minimize the threat of interactions between wild and aquaculture salmon have not yet been implemented. The threat of these interactions is considered critical, given the fact that wild salmon stocks within the DPS are at low abundance levels and are particularly vulnerable to genetic intrusion or other disturbances caused by escaped aquaculture salmon.

Many of the threats to the Gulf of Maine DPS of Atlantic salmon evaluated during this review have been reduced significantly through the considerable efforts put forth by the State of Maine and public and private sector partners. The fact remains, however, that under current circumstances, it is the opinion of the BRT that the Gulf of Maine DPS of Atlantic salmon is in danger of extinction. Atlantic salmon in the Gulf of Maine DPS exhibit critically low spawner abundance and poor marine survival. These two key recovery factors are further compromised by the increased presence of threats which have been documented to negatively impact salmon stocks. Currently these threats include artificially reduced water levels, diseases and parasites, recreational and commercial fisheries, sedimentation, and genetic intrusion by commercially raised Atlantic salmon.