Adam Moles

Effects of fluctuating temperature on mortality, stress, and energy reserves of juvenile coho salmon

Abstract The effects of fluctuating diel temperature cycles on survival, growth, plasma cortisol and glucose concentrations, liver weight, and liver glycogen of juvenile coho salmon Oncorhynchus kisutch were determined. Temperature cycles (10–13°, 9–15°, 8–17°, and 6.5–20°C) were selected to simulate observed temperatures in clear-cuts of southeastern Alaska. Different levels of feeding, including starvation, were used in each of the tests. LT50s (peak temperature within a cycle producing 50% mortality) were 28°C for age-0 fish (350 mg) and 26°C for age-II fish (22-g presmolts). Cyclic temperatures for 40 d, averaging 11°C daily, did not influence growth of age-0 fish on any food ration as compared to controls held at a constant 11°C. Plasma cortisol and glucose concentrations were significantly greater in fish maintained for 20 d in the 6.5–20°C cycle but not different in fish in 10–13° and 9–15°C cycles or a constant 11°C. These elevated concentrations may be indicators of long-term stress. Plasma corti...

Impacts to Pink Salmon Following the Exxon Valdez Oil Spill: Persistence, Toxicity, Sensitivity, and Controversy

Injury to a species resulting from long-term exposure to low concentrations of pollutants is seldom noted or even tested. One of the products of the Exxon Valdez oil spill was the first report of damage to eggs and larvae of pink salmon (Oncorhynchus gorbuscha) following long-term exposure to low concentrations of weathered crude oil. These life stages were previously thought to be highly resistant to injury from oil. Growth rate among migrating fry was depressed, and the population was reduced via size-dependent mortality. Elevated egg mortality in oiled streams continued for at least 4 years after the spill. Laboratory tests verified that embryos are sensitive to long-term exposure to weathered oil in the low parts per billion range. These results are compared with those of studies conducted by investigators funded by Exxon Corporation and, where controversy exists, we attempt to reconcile the studies. These findings are important to the pink salmon fisheries of Prince William Sound (PWS) and are also broadly applicable to toxicity and impact from nonpoint source pollution of urban estuaries.

Sediment preference in juvenile pacific flatfishes

Abstract Behavioural preference tests were used to determine if sediment selection played a role in habitat choice. Four species of juvenile pleuronectids were given a choice of eight sediments in a carousel and final choices were recorded after 20 h. Juvenile flatfishes demonstrated strong selection for sediments less than 500 μm. Juvenile starry flounder (Platichthys stellatus) selected larger particles with increasing fish size. Starry flounder under 25 mm in length chose mud, 50–80 mm fish chose mud and mixed mud sediments and larger juveniles (>150 mm) confined themselves to find sand. Juvenile halibut (Hippoglossus stenolepis) at 50–80 mm preferred a combination of mud and fine sand and were spatially segregated. Yellowfin sole (Pleuronectes asper) at 50–80 mm showed a slight preference for mud and mixed mud sediments over sand, a selection that became stronger in larger (>150 mm) fish. Juvenile rock sole (Pleuronectes bilineatus) at 50–80 mm preferred substrata of sand and mixed sand nearly 90% of the time. All species seldom selected sediments which were too coarse to allow the flatfishes to bury themselves, such as granular or pebble substrata. The results of these laboratory studies can be used to predict the distribution of juvenile flatfishes in a nursery area.

Sensitivity of Alaskan Freshwater and Anadromous Fishes to Prudhoe Bay Crude Oil and Benzene

Abstract The sensitivity of various species and life stages of Alaskan freshwater and anadromous fishes to benzene and the water-soluble fraction of Prudhoe Bay crude oil was determined with 96-hour toxicity tests. Freshwater juveniles of the six salmonid species tested had similar sensitivities. Median tolerance limits (TLms) of these salmonids for crude oil ranged from 2.7 to 4.4 mg/liter; TLms of benzene ranged from 11.7 to 14.7 μl/liter. Threespine sticklebacks and, to a lesser extent, slimy sculpins were more tolerant than salmonids and had larger TLms: Threespine sticklebacks had a crude-oil TLm of 10.4 mg/liter and a benzene TLm of 24.8 μl/liter; slimy sculpins had a crude-oil TLm of 6.44 mg/liter and a benzene TLm of 15.4 μl/liter. Eggs of pink salmon and coho salmon were quite tolerant to crude oil (TLm > 12 mg/liter) and benzene (TLm = 339–542 μl/liter). Emergent fry were the most sensitive freshwater stage (crude-oil TLm = 8.0 mg/liter; benzene TLm = 12.3–17.1 μl/liter). Out-migrant salmonid...

Chapter 5 – The Exxon Valdez Oil Spill

This chapter discusses the largest marine oil spill in the United States and the largest spill in a sub Arctic ecosystem; however, the damage from the Exxon Valdez oil spill (EVOS) was due as much to when and where it happened as it was to the size of the spill. The oil inundated seabird, sea otter, and harbor seal habitat just prior to their breeding seasons and that of many other vulnerable species. Oil persisted beyond a decade in surprising amounts and in toxic forms. The residual oil was sufficiently bioavailable to induce chronic biological exposures to near shore species and oil had both short-term and long-term effects on a wide variety of species, with prolonged effects on species associated with oiled sediments. The Exxon Valdez spill is the most thoroughly studied oil spill in the history. The conceptual models based on laboratory tests and previous oil spills proved inadequate for describing or predicting the outcome of the Exxon Valdez oil spill. The nature confounded the tracking and observed changes over time, this spill was not burdened with the layering of other spills, industrial effluents, or urban development and sewage.

Effects of Crude Oil and Naphthalene on Growth, Caloric Content, and Fat Content of Pink Salmon Juveniles in Seawater

Abstract Juvenile pink salmon Oncorhynchus gorbuscha were exposed for 40 days to stable, sublethal concentrations of naphthalene (<0.80 mg/liter) and the water-soluble fraction of Cook Inlet crude oil (<0.87 mg/liter total aromatic hydrocarbons). All fish were fed equal daily rations of Oregon Moist Pellet Formula II. Concentrations (percentage of the 96-hour LC50, median lethal concentration) of 10% naphthalene and 14% water-soluble fraction of crude oil did not affect wet weight or length of exposed fish. At higher concentrations, however, growth per day determined from wet weight decreased with increased toxicant concentration. Change in length of the fish was not a sensitive measure of toxicity. Fish exposed for 40 days to concentrations of toxicants as low as 33% of the 96-hour LC50 weighed significantly less than control fish (P < 0.05). Juveniles exposed to the water-soluble fraction of crude oil had slower growth rates than those exposed to the same concentration (percentage of the LC50) of naphth...

Sensitivity of Parasitized Coho Salmon Fry to Crude Oil, Toluene, and Naphthalene

Abstract The effect of parasitism by glochidia of Anodonta oregonensis (a freshwater mussel) on the sensitivity of coho salmon fry, Oncorhynchus kisutch, to oil was determined by exposing fry with different levels of parasitism to several concentrations of either the water-soluble fraction of Prudhoe Bay crude oil or the aromatic hydrocarbons toluene and naphthalene. Fry infested with 20–35 glochidia were significantly (P < 0.05) more sensitive to each of the toxicants than uninfested fish. Sensitivity increased linearly with increased parasite numbers. Interpretation and application of results of toxicity tests should take into account the kinds and intensities of parasitism found both in the test animals and in the wild populations of fish.

SENSITIVITY OF 39 ALASKAN MARINE SPECIES TO COOK INLET CRUDE OIL AND NO. 2 FUEL OIL

ABSTRACT The sensitivities of 39 subarctic Alaskan species of marine fish and invertebrates to water-soluble fractions of Cook Inlet crude oil and No. 2 fuel oil were determined. This is the largest group of animals ever tested under similar test conditions with the same petroleum oils and analytical methods. Organisms bioassayed represent several habitats, six phyla, and 39 species including fish (9), arthropods (9), molluscs (13), echinoderms (4), annelids (2), and nemer-teans (2). Sensitivities were determined by 96-hour static bioassays. Concentrations of selected aromatic hydrocarbons were determined by gas chromatography; concentrations of paraffins were determined by infrared spectrophotometry. Although sensitivity generally increased from lower invertebrates to higher invertebrates, and from higher invertebrates to fish, sensitivity was better correlated to habitat. Pelagic fish and shrimp were the most sensitive animals to Cook Inlet crude oil with 96-h median tolerance limits (TLms) from 1–3 mg...

Non-avoidance of hydrocarbon laden sediments by juvenile flatfishes

Behavioural tests were used to determine whether juvenile flatfishes were capable of detecting and avoiding sediment containing various concentrations of petroleum hydrocarbons. Three species of juvenile Alaskan flatfishes: rock sole (Pleuronectes bilineatus), yellowfin sole (P. asper), and Pacific halibut (Hippoglossus stenolepis) were tested in laboratory chambers containing contaminated mud or sand offered in combination with clean mud, sand or granule. The flatfishes were able to detect and avoid heavily oiled (2%) sediment, but they did not avoid lower concentrations of oiled sediment (0.05%). Oiled sediment was favoured over unoiled sediment if the unoiled sediment was of the grain size not preferred by that species. Oiled sand or mud was always preferred unoiled granule. The observed lack of avoidance at concentrations likely to occur in the environment may lead to long-term exposure to contaminated sediment following a spill. Recruitment of juveniles may be affected if the exposure to oil is long enough to affect growth and survival.

Reduced growth of coho salmon fry exposed to two petroleum components, toluene and naphthalene, in fresh water

Abstract Coho salmon, Oncorhynchus kisutch, fry were exposed for 40 days to stable, sublethal concentrations of toluene (0.4, 0.8, 1.6, 3.2, 5.8 μl/liter) and naphthalene (0.2, 0.4, 0.7, 1.4 mg/liter) in fresh water. All fry were fed equal daily rations of Oregon Moist Pellet Formula II. Dry weights, wet weights, and lengths of fry exposed to the two highest concentrations of each toxicant for 40 days were significantly less than controls (P < 0.01). Growth per day, determined from weights and lengths, decreased linearly with increased concentrations. Fry exposed to naphthalene had a slower growth rate than fry exposed to equivalent concentrations (percentage of the 96-hour median lethal concentration or LC50) of toluene. Concentrations 18% of the LC50 of naphthalene and 26% of the LC50 of toluene had no effect on dry weight, wet weight, or length of exposed fry.