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Morton, A., R. Routledge, and M. Krkosek. 2008. Sea louse infestation in wild juvenile salmon and Pacific herring associated with fish farms off the east-central coast of Vancouver Island, British Columbia. North American Journal of Fisheries Management. Published online March 31, 2008. Abstract: Reports of infestations of sea lice Lepeophtheirus salmonis and Caligus clemensi in juvenile salmonids in Pacific Canada have been restricted to pink salmon Oncorhynchus gorbuscha and chum salmon O. keta from one salmon-farming region, the Broughton Archipelago of British Columbia. Here, we report on 2 years of sea louse field surveys of wild juvenile pink and chum salmon, as well as wild sockeye salmon O. nerka and larval Pacific herring Clupea pallasii, in another salmon farming region, the Discovery Islands region of British Columbia. For pink and chum salmon we tested for the dependency of sea louse abundance on temperature, salinity, sampling period, host species, and farm exposure category. For both louse species, farm exposure was the only consistently significant predictor of sea lice abundance. Fish exposed to salmon farms were infected with more sea lice than those in the peripheral category. Sea louse abundance on sockeye salmon and Pacific herring followed the same trends, but sample sizes were too low to support formal statistical analysis. The Pacific herring were translucent and lacked scales, and they were primarily parasitized by C. clemensi. These results suggest that the association of salmon farms with sea lice infestations of wild juvenile fish in Pacific Canada now extends beyond juvenile pink and chum salmon in the Broughton Archipelago. Canada's most abundant and economically valuable salmon populations, as well as British Columbia's most valuable Pacific herring stock, migrate through the Discovery Islands; hence, parasite transmission from farm to wild fish in this region may have important economic and ecological implications. Krkoek, M., J.S. Ford, A. Morton, S. Lele, R.A. Myers, and M.A. Lewis. 2007. Declining Wild Salmon Populations in Relation to Parasites from Farm Salmon. Science 14 December 2007: Vol. 318. no. 5857, pp. 1772 - 1775. DOI: 10.1126/science.1148744 Abstract: Rather than benefiting wild fish, industrial aquaculture may contribute to declines in ocean fisheries and ecosystems. Farm salmon are commonly infected with salmon lice (Lepeophtheirus salmonis), which are native ectoparasitic copepods. We show that recurrent louse infestations of wild juvenile pink salmon (Oncorhynchus gorbuscha), all associated with salmon farms, have depressed wild pink salmon populations and placed them on a trajectory toward rapid local extinction. The louse-induced mortality of pink salmon is commonly over 80% and exceeds previous fishing mortality. If outbreaks continue, then local extinction is certain, and a 99% collapse in pink salmon population abundance is expected in four salmon generations. These results suggest that salmon farms can cause parasite outbreaks that erode the capacity of a coastal ecosystem to support wild salmon populations. Krkosek, M., M.A. Lewis, A. Morton, L.N. Frazer, and J.P. Volpe. 2006. Epizootics of wild fish induced by farm fish. Proceedings of the National Academy of Sciences. PNAS published October 4, 2006, 10.1073/pnas.0603525103 Download paper - Open Access at PNAS Abstract: The continuing decline of ocean fisheries and rise of global fish consumption has driven aquaculture growth by 10% annually over the last decade. The association of fish farms with disease emergence in sympatric wild fish stocks remains one of the most controversial and unresolved threats aquaculture poses to coastal ecosystems and fisheries. We report a comprehensive analysis of the spread and impact of farm-origin parasites on the survival of wild fish populations. We mathematically coupled extensive data sets of native parasitic sea lice (Lepeophtheirus salmonis) transmission and pathogenicity on migratory wild juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon. Farm-origin lice induced 9-95% mortality in several sympatric wild juvenile pink and chum salmon populations. The epizootics arise through a mechanism that is new to our understanding of emerging infectious diseases: fish farms undermine a functional role of host migration in protecting juvenile hosts from parasites associated with adult hosts. Although the migratory life cycles of Pacific salmon naturally separate adults from juveniles, fish farms provide L. salmonis novel access to juvenile hosts, in this case raising infection rates for at least the first ~2.5 months of the salmon's marine life (~80 km of the migration route). Spatial segregation between juveniles and adults is common among temperate marine fishes, and as aquaculture continues its rapid growth, this disease mechanism may challenge the sustainability of coastal ecosystems and economies. Morton, A., and R.D. Routledge. 2006. Fulton's Condition Factor: Is it a valid measure of sea lice impact on juvenile salmon? North American Journal of Fisheries Management 26:56-62. Abstract: Condition factor formulas have been developed and are used to assist in assessing the state of fish health. Fulton's condition factor has been used to measure anthropogenic impacts on fish, such as oil spills, and has provided results that, at times, are contentious. Recently, it has been used to suggest that infestation rates of sea lice Lepeophtheirus salmonis currently reported for juvenile pink salmon Oncorhynchus gorbuscha and chum salmon O. keta in the Broughton archipelago, British Columbia, may have no impact on fish health. Here, we show that Fulton's condition factor values will remain high in salmon fry lethally infected with sea lice until shortly before death. Furthermore, we report that as condition factor values declined, the affected fish exhibited high predator risk behavior. We conclude that Fulton's condition factor does not provide a reliable indicator of the impact of sea lice infestations on juvenile pink and chum salmon. Morton, A.B., and Routledge, R. 2005. Mortality rates for juvenile pink Oncorhynchus gorbuscha and chum O. keta salmon infested with sea lice Lepeophtheirus salmonis in the Broughton Archipelago. Alaska Fishery Research Bulletin 11(2):146-152. Download paper (367KB) Abstract: Wild juvenile pink Oncorhynchus gorbuscha and chum salmon O. keta were captured and sorted by the number of sea lice Lepeophtheirus salmonis infecting each fish. These fish were placed in groups of 60 in flowthrough containers immersed in seawater near the site of capture. There were 3-4 replicates for each infection category and 3 consecutive trials or Series run to assess the impact of sea lice on short-term fish mortality. Control groups of lice-free fish were included to measure handling and containment effects. In each trial or Series, significantly more fish died in the categories with sea lice than in the lice-free category. The majority of fish infected with motile-stage sea lice died. These observations indicate that short-term mortality of wild juvenile pink and chum salmon is increased by infestations of 1-3 sea lice. Ford, J.K.B., G.M. Ellis, D.R. Matkin, K.C. Balcomb, D. Briggs, and A.B. Morton. 2005. Killer whale attacks on minke whales: Prey capture and antipredator tactics. Marine Mammal Science 21(4):603-618. Download paper (1.5MB) Abstract: We describe nine incidents of predation or attempted predation of minke whales (Balaenoptera acutorostrata) by mammal-hunting "transient" killer whales (Orcinus orca) in coastal waters of British Columbia, Washington, and southeastern Alaska. Pursuits of minke whales were characterized by prolonged chases on a straight heading at velocities of 15-30 km/h. In four of the nine cases the adult-sized minke whale gradually outdistanced the killer whales, which abandoned the high-speed pursuit after 0.5-1 h. In one case the minke beached itself and died. Four attacks were successful. In one instance a subadult minke was killed in open water following a chase. In two cases the fleeing minke entered a confined bay and was killed by the killer whales. One adult minke was taken after apparently attempting to seek cover beside a large sailboat. Minke whales made no attempt to physically defend themselves and were killed by repeated ramming or by asphyxiation. Although killer whales are capable of sprinting speeds greater than those of minke whales, it appears that adult minkes can maintain higher sustained speeds and evade capture if sufficient space for an extended escape trajectory is available. Successful predation of minke whales in coastal waters is rare compared to pinnipeds and small cetaceans, the main prey of transient killer whales. Krkosek, M., A. Morton, and J.P. Volpe. 2005. Nonlethal assessment of juvenile pink and chum salmon for parasitic sea lice infections and fish health. Transactions of the American Fisheries Society 134(3):711-716. Download paper (51 KB) Abstract: Industrial salmon farming has been correlated with infestations of parasitic sea lice Lepeophtheirus salmonis in adjacent wild juvenile salmonids and declines of sympatric wild salmonid populations. Prohibitively large financial, human, and logistical resource requirements prevent the implementation of long-term, large-scale monitoring programs to assess the effect of farms on wild salmonids. We report a novel nonlethal sampling procedure for quantifying louse abundances and measures of fish health on wild juvenile pink salmon Oncorhynchus gorbuscha and chum salmon O. keta during their early marine life history phase. The method significantly reduces the resource requirements of sampling programs and provides a desirable nonlethal alternative for studying depressed or threatened populations. The simplicity of the protocol facilitates public participation, further decreasing costs while increasing the potential spatiotemporal coverage and resolution of future research-monitoring programs. Morton, A., R.D. Routledge, and R. Williams. 2005. Temporal patterns of sea louse infestation on wild pacific salmon in relation to the fallowing of Atlantic salmon farms. North American Journal of Fisheries Management 25(3):811-821. Abstract: We report on a 3-year study of the infestation rates of the sea louse, Lepeophtheirus salmonis, on wild juvenile pink salmon Oncorhynchus gorbuscha and chum salmon O. keta in the Broughton Archipelago, British Columbia. In 2002, the British Columbia Ministry of Agriculture, Fisheries, and Food ordered farm fallowing (i.e., the removal of farmed Atlantic salmon Salmo salar from net-cages) along the presumed migration route of wild juvenile Pacific salmon in this area. The goal was to protect wild juvenile fish from sea louse infestation. We assessed the effectiveness of this decision by comparing sea louse infestation rates on wild juvenile salmon near three Atlantic salmon farm sites prior to, during, and after fallowing. Overall, L. salmonis levels were significantly reduced (P < 0.0001) at the study sites during fallowing but returned to the original level after fallowing. The decline was age specific. While the abundance of the earliest attached sea louse phase (the copepodid stage) declined by a factor of 42, the mean abundance of adult L. salmonis did not decline significantly. Changes in salinity and temperature could not account for the decline. This study provides evidence that the fallowing of Atlantic salmon farms during spring juvenile salmon migrations can be an effective conservation and management tool for protecting wild salmon. While this correlation adds to the increasing weight of evidence linking Atlantic salmon farms to increased parasite loads on wild salmon, greater cooperation between researchers and farmers will be necessary to isolate the causal mechanisms and provide safe seaward passage to wild juvenile salmon. Morton, A., R. Routledge, C. Peet, and A. Ladwig. 2004. Sea lice (Lepeophtheirus salmonis) infection rates on juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon in the nearshore marine environment of British Columbia, Canada. Canadian Journal of Fisheries and Aquatic Sciences 61(2):147-157. Download paper (349KB) Press Release, March 3, 2004 Abstract: This study compared sea lice (Lepeophtheirus salmonis) infestation rates on juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon in five nearshore areas of the British Columbia coast selected on the basis of proximity to salmon farms. A 10-week study in the Broughton Archipelago found sea lice were 8.8 times more abundant on wild fish near farms holding adult salmon and 5.0 times more abundant on wild fish near farms holding smolts than in areas distant from salmon farms. We found that 90% of juvenile pink and chum salmon sampled near salmon farms in the Broughton Archipelago were infected with more than 1.6 lice·(g host mass)-1, a proposed lethal limit when the lice reach mobile stages. Sea lice abundance was near zero in all areas without salmon farms. Salinity and temperature differences could not account for the higher infestation rates near the fish farms. The most immature life stages dominated the lice population throughout the study, suggesting the source of lice was a stationary, local salmonid population. No such wild population could be identified. The evidence from this control-impact study points to a relationship between salmon farms and sea lice on adjacent, wild, juvenile salmon. Morton, A.B. and J. Volpe. 2002. A Description of Escaped Farmed Atlantic Salmon Salmo salar Captures and Their Characteristics in One Pacific Salmon Fishery Area in British Columbia, Canada, in 2000. Alaska Fisheries Research Bulletin Vol. 9(2):102-110. Download paper (137KB) Since 1995, the Canadian salmon farming industry as a whole has reported losing an average of 46,255 Atlantic salmon Salmo salar annually into the coastal waters of British Columbia. While the number of fish lost is arguably much higher, it is unarguable that the fate of these fish is largely unknown. This study was conducted on the fishing grounds of British Columbia by contacting commercial fishers frequently via VHF radio and boat visits. Atlantic salmon were collected directly from fishers, packers, and a processing plant. The goal of this project was to enumerate the number of Atlantic salmon caught by commercial fishers in Pacific Management Area 12, a region of intense salmon farm activity. Further, we wished to examine the condition of these escaped farm salmon to aid managers in determining their ability to survive in the wild. A total of 10,826 Atlantic salmon were caught in the 17 days of open fishing periods during this study, August 2, 2000 through September 22, 2000, by troll, seine, and gillnet gear. The mean fork length and weight of the sampled Atlantic salmon were 75.0 cm (±5.1 cm) and 4.8 kg (±1.3 kg), respectively. Autopsies on 775 whole or partial Atlantic salmon found identifiable stomach contents in 3.9% of the sample overall, and up to 24.4% at some sampling locations. Eighteen fish (2.3%) showed signs of sexual maturity. One group of escaped Atlantic salmon was sampled weekly over a fourteen-day interval, days 1, 8, 14, and an increase in foraging success was recorded. Gillnets were the most successful gear type in recovering escaped farm salmon. The present passive reporting system of Fisheries and Oceans Canada underestimates Atlantic salmon escapes. This study recorded 40.8% more Atlantic salmon caught in the 8 week study period in Pacific Management Area 12 by commercial fishers than the federal Fisheries and Oceans Canada's passive monitoring program. Morton, A. B. and H.K. Symonds. 2002. Displacement of Orcinus orca (L.) by high amplitude sound in British Columbia, Canada. ICES Journal of Marine Science, 59: 71-80. Download paper from the ICES Science Direct website (per per view) ABSTRACT: Whale displacement by acoustic ''pollution'' has been difficult to document, even in cases where it is strongly suspected, because noise effects can rarely be separated from other stimuli. Two independent studies on the natural history of killer whales (Orcinus orca) monitored frequency of whale occurrence from January 1985 through December 2000 in two adjacent areas: Johnstone Strait and the Broughton Archipelago. Four high-amplitude, acoustic harassment devices (AHDs) were installed throughout 1993 on already existing salmon farms in the Broughton Archipelago, in attempts to deter predation on fish pens by harbour seals (Phoca vitulina Linnaeus). While whale occurrence was relatively stable in both areas until 1993, it then increased slightly in the Johnstone Strait area and declined significantly in the Broughton Archipelago while AHDs were in use. Both mammal-eating and fish-eating killer whales were similarly impacted. Acoustic harassment ended in the Broughton Archipelago in May 1999 and whale occurrence re-established to baseline levels. This study concludes that whale displacement resulted from the deliberate introduction of noise into their environment. |
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| Morton, A. 2000. Occurrence, photo-identification and prey of Pacific white-sided dolphins (Lagenorhyncus obliquidens) in the Broughton Archipelago, Canada 1984-1998. Marine Mammal Science, 16(1): 80-93. Download
paper (602 KB) | ||||||||||||
| Morton,
A. B., J.C. Gale. and R.C. Prince. 1986. Sound
and behavioral correlation in captive Orcinus orca. In: Kirkevold, B.C.
and Lockhard, J.S. (eds.) Behavioral biology of killer whales. Alan R.
Liss, Inc. New York. pp. 303-333. In this study we looked at the percentage emission rather than the absolute occurrence of sounds. Instead of concentrating on one or two individual sounds we took a broad look at the overall usage of the sound in different behavioral activities of Orcinus orca. With this approach a relationship was found between sounds and behaviora states, i.e., "tranquility," "play" and "distress." | ||||||||||||
| Ford, J.K.B., G. Ellis, L. Barret-Lennard, A.B. Morton, R. Palm and K.C. Balcomb. 1998. Dietary specialization in two sympatric populations of killer whales (Orcinus orca) in coastal British Columbia and adjacent waters. Canadian Journal of Zoology 76(8): 456-1471. Download paper (372KB) ABSTRACT: Two forms of killer whale (Orcinus orca), resident and transient, occur sympatrically in coastal waters of British Columbia, Washington State, and southeastern Alaska. The two forms do not mix, and differ in seasonal distribution, social structure, and behaviour. These distinctions have been attributed to apparent differences in diet, although no comprehensive comparative analysis of the diets of the two forms had been undertaken. Here we present such an analysis, based on field observations of predation and on the stomach contents of stranded killer whales collected over a 20-year period. In total, 22 species of fish and 1 species of squid were documented in the diet of resident-type killer whales; 12 of these are previously unrecorded as prey of O. orca. Despite the diversity of fish species taken, resident whales have a clear preference for salmon prey. In field observations of feeding, 96% of fish taken were salmonids. Six species of salmonids were identified from prey fragments, with chinook salmon (Oncorhynchus tshawytscha) being the most common. The stomach contents of stranded residents also indicated a preference for chinook salmon. On rare occasions, resident whales were seen to harass marine mammals, but no kills were confirmed and no mammalian remains were found in the stomachs of stranded residents. Transient killer whales were observed to prey only on pinnipeds, cetaceans, and seabirds. Six mammal species were taken, with over half of observed attacks involving harbour seals (Phoca vitulina). Seabirds do not appear to represent a significant prey resource. This study thus reveals the existence of strikingly divergent prey preferences of resident and transient killer whales, which are reflected in distinctive foraging strategies and related sociobiological traits of these sympatric populations. High numbers of Lepeophtheirus salmonis on juvenile pink salmon in British Columbia, Canada. American Society of Limnology and Oceanography Conference, Victoria, BC, June 13, 2002 ABSTRACT: Although historically an innocuous parasite, sea lice infections of wild salmon have become a critical issue in areas where wild and farm salmon share marine habitat. It is generally believed that farm salmon initially acquire sea lice (Lepeophtheirus salmonis) from adult wild salmon stocks returning from the sea to spawn. Under natural conditions, this species of sea louse dies when wild salmon enter freshwater to spawn, depriving this salmon-specific parasite of a host. Now it would appear salmon farms could offer sea lice artificial, inshore, over-wintering habitat. Widespread reports of Lepeophtheirus salmonis infestation of farm salmon suggests that sea lice respond favourably to the ideal parasitic conditions, i.e. dense crowding, stationary hosts and 24-hour lighting, found on salmon farms. Sea louse egg-production peaks in spring just as wild salmon smolts encounter the farms on their out-migration, making infection possible. The number, age class, sex and species of lice were examined on 923 juvenile wild salmon caught from June 5 through August 15th, 2001 at 48 sites in the heavily salmon-farmed Broughton Archipelago. The data presented in this paper indicate the highest infection rates by early chalimus stage lice occurred at and immediately west of aquaculture pens containing adult Atlantic salmon. |
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