Mid-Term Exam Questions Used in the Past

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Recent phylogenetic trees describing the relationships among salmonids based on molecular genetics indicate that sockeye, chum and pink salmon are grouped together and that rainbow and cutthroat trout form another group. What morphological, life history and behavioral traits support this conclusion? What traits argue against this conclusion?

Describe and explain the similarities and differences between salmon and typical Canadian freshwater fishes in egg size, gonad:body weight ratio, and spawning date.

How do Pacific salmon compare to other North American freshwater fishes in terms of body size, fecundity, and egg size? What aspects of their life history and behavior might explain these patterns?

Among diadromous species, anadromy tends to dominate at high latitudes and catadromy at low latitudes. It has been hypothesized that the differences between marine and freshwater production explain these patterns. However, in the Pacific Northwest the starry flounder, Platichthys stellatus, seems to be facultatively catadromous. That is, adults spawn in marine environments but juveniles may rear in rivers. First, explain why flounder might make such a migration. Second, describe experiments or other investigations that test your explanation. The investigation need not address all aspects of this paradox.

Semelparous species of salmonids tend to be more abundant than iteroparous species. Propose an explanation for this pattern.

The fall spawning Oncorhynchus species are almost always semelparous, whereas the spring spawning species have the potential for iteroparity. Propose an explanation for this pattern and provide a rationale for your hypothesis.

You are employed by a government agency and are charged with designing a program to examine the uptake of pollutants by juvenile salmon. What would be your levels of concern for the health of the six most numerous species of North American Pacific salmonids (omit cutthroat, Apache, Gila, Dolly Varden, etc.), given point sources of pollution in (1) an estuary, and (2) a stream. For each pollution source, indicate the relative vulnerabilities of the species.

You are a fisheries biologist hired as a consultant by a development company which is planning to build the world's largest shopping mall at a site which impacts a stream containing the six most common Pacific species of Oncorhynchus. The project is likely to decrease flows during the summer and increase the severity and frequency of floods during the winter. Discuss the relative vulnerability of each species to this project, considering both juvenile and adult life history stages.

An early simulation model of salmon homing on the high seas was based on the following assumptions. Indicate which are reasonable (obviously, all are generalizations) and give more accurate values for any that you consider unreasonable.

            a. Salmon begin their homeward migration 2200 km from shore, on the same latitude as their home river

            b. Salmon swim 4.6 km/h at sea.

            c. Salmon may search for their home river for 175 days. Those not finding home within that period may be assumed to be lost.

            d. Salmon coming within 64 km of the mouth of their home river may be assumed to use olfaction to locate it.

            e. The proportion of salmon tagged at sea as maturing fish and recovered in coastal waters or rivers may be taken to indicate the proportion of successful migrants.That is, others may be considered disoriented and lost at sea.

Many salmon appear to migrate accurately and quickly from the open ocean to their natal streams. Peter Larkin proposed that this was because (1) they know their location in the ocean (map sense), (2) they know the direction of home (compass sense), and (3) they know when to leave to get there at the right time (calendar sense). What evidence could be used to support these assertions? What evidence could be used to argue against them?(You need to address only two of the three points.)

The migration of salmon from coastal waters through an estuary and upriver involves many changes in physical environment, physiology and behavior. Salmon commonly spend a few days to weeks in an estuary before migrating upriver. Propose an hypothesis to explain this apparent delay and describe what patterns of vertical and horizontal movements the fish would display in the estuary that would be consistent and inconsistent with the hypothesis. That is, if you used ultrasonic telemetry to track salmon, what results would support or falsify the hypothesis.

Migrating salmon experience many changes in their physical environments as they go from the open ocean to fresh water. Discuss these changes and how mechanisms of orientation may vary between the two environments.

The flow and temperature regimes of the Columbia River have changed during this century.Peak flows formerly occurred in spring, driven by snow-melt. This water is now stored in spring to be released in winter for hydroelectric power production. Assuming that spring (e.g., May-June) flows are lower than in past years and spring-summer temperatures are warmer, what effect might be seen in the migration (arrival and upstream rate of travel) of adult salmon? Explain...

When salmon and trout enter freshwater on their homing migration, they typically cease to feed. The fish in some populations spawn only a few days later whereas others may remain in freshwater for six months or more before spawning. (a) What environmental factors may select for early entry into freshwater? (b) How can adults minimize their energy loss while holding in freshwater?

How did Brett arrive at the conclusion that sockeye salmon migrating up the Fraser River swim about 4.3 km/h, relative to the water?

Summarize the three key components of the olfactory imprinting hypothesis proposed by Arthur Hasler and the pheromone hypothesis of Hans Nordeng. Are these hypotheses mutually exclusive?

It has been hypothesized that homing salmon are attracted to the odors of juveniles of their own species residing in the river or migrating to sea from it. These odors are hypothesized to be not only species-specific but actually unique to each population.Laboratory experiments indeed indicate that salmon can distinguish the odors of their population from those of other populations. For pink, chum, sockeye and steelhead, evaluate the utility of population-specific odors as a clue for homing to the natal stream. That is, would the patterns of life history and distribution of each of the four species tend to facilitate or hinder use of population-specific odors for homing, and why?

You have been hired as a consultant on a conservation plan for a species of sea snake.The snakes arrive on beaches of small islands, lay their eggs, and leave. You need to know whether the snakes on each island form independent populations or whether they are all one intermingling population. You would also like to know how the snakes determine on which island to lay their eggs. Propose experiments to shed light on these questions.

Shapovalov and Taft reported that steelhead strayed less often between Waddell and Scott creeks than did coho salmon. Propose a plausible explanation for this pattern.

What variation in homing/straying would you predict among the species of anadromous salmon or trout, based on your knowledge of their life history and ecology? Indicate species predicted to stray the most, least, and explain these predictions.

The great majority of salmon that live to maturity return to spawn in their natal stream. However, some stray and spawn elsewhere. Provide (a) a mechanistic (proximate) explanation for straying and (b) an evolutionary (ultimate) explanation that reveals the way in which straying can increase the reproductive success of individual salmon, relative to salmon that home.

Female salmon are not markedly less aggressive than males yet they show much less development of the jaws and teeth used in aggression than do males. A simple explanation might be that females use most of their energy in gonad development and so have less left for morphological changes. Is this a sufficient explanation or are other factors involved?

Define the Operational Sex Ratio and explain the relevance of this term to salmon spawning behavior. Having done so, then discuss the merits of a regulation whereby steelhead fishermen would be allowed to keep males but would have to release all females (assume that the fishermen could distinguish between the sexes and successfully release the females).

Discuss the costs and benefits of achieving large body size for the reproductive success of male and female salmon.

Sexual selection in salmon results primarily from competition among males for access to females and among females for access to spawning sites, instead of from the active choice of mates based on display characters (e.g., tropical birds often chose mates based on extravagant plumage). (a) How might characteristics of the life-history or spawning environment of salmon cause intra-sexual selection to be more important than inter-sexual (epigamic) selection? (b) What are the ways in which male and female salmon may exercise some degree of mate choice?

Mature Pacific salmon vary greatly in age, body size and shape (e.g., hump and snout size). Presumably this variation is maintained through the processes of natural and sexual selection. What are some of the selective pressures which may be important in the expression of these traits, and how do the traits affect reproductive success.

Pacific salmon populations often show variation in age at maturity, and the mean age and level of variation commonly varies between males and females within a given population. Detail the advantages and disadvantages of maturing at specific ages that result in fish not all maturing at the same age, and explain why patterns differ between males and females.

In Glacier Bay, southeast Alaska, glaciers have receded recently, creating short freshwater habitats. Based on your knowledge of the life histories of the salmon and trout species, and your knowledge or assumptions about the habitat being made available to them, which species are the most and least likely to successfully colonize these new habitats? State explicitly the aspects of life history and habitat use that justify your answer.

Pink salmon all mature at age 2 and are widely believed to have high rates of straying.Chinook salmon show a wide range of ages at maturity and seem to stray only rarely. Provide explanations for the difference in straying between these species, and discuss whether age at maturity has anything to do with it.

In the Weaver Creek spawning channel there is (was) aggression by males and females of two species, sockeye and chum salmon. Hypothesize what levels of aggression males and females of each species would display towards males and females of their own and the other species. Explain your reasoning, based on the resources for which the fish compete.

Define the Operational (or Operating) Sex Ratio and explain the relevance of this term to salmon spawning behavior. If a gillnet fishery, with a mesh size designed to catch more males than females, was insituted on a pink salmon population, what might be the effects on the population’s abundance and the behavior on the spawning grounds?

Bear predation on spawning adult salmon can become quite intense in areas where both animals occur in large numbers such as SE Alaska. It has been observed that bears generally kill larger fish and more males than females. Propose two different explanations for these patterns and propose an experiment or other means to discriminate between the two hypotheses.

It has been shown that dead salmon are an important part of watershed ecology. Some predators and scavengers rely on salmon carcasses and nutrients from salmon are incorporated into streamside vegetation and in-stream plants and animals. Given what you know of general salmonid characteristics and life history would you expect pink salmon or coho to have a higher nutrient contribution to a river? Why? What about steelhead or coho? Why?

A negative relationship has been observed between numbers of returning adult sockeye salmon and growth of juvenile sockeye in lakes. Is this enough evidence to conclude that adult carcasses are having a fertilizing effect on the lake? Why or why not?

Salmon hatcheries usually have an egg quota (i.e. a required number of fertilized salmon eggs for each propagated species in each spawning season) which is typically met early in the spawning season, since hatchery managers can never be certain that more salmon will show up at the hatchery later in the season. Given that migration timing and other life history characteristics are heritable (i.e. in part determined genetically) and given what you know about patterns of migration timing in salmonids, how do you think this practice would affect patterns of migration in the hatchery population? On what other adult life history or morphological characteristics would this practice have an effect? In what way?

During a recent sockeye salmon fishing trip to the Russian River, Alaska, you discover you did not do your homework. You arrive at the river to find no salmon, only a few crusty locals saying that you came between ‘runs.’ You are told that the first run, comprised mostly of small-bodied individuals, comes early in the season and migrates high into the watershed, spawning in small tributaries. The second run, with much larger individuals on average, comes later in the season and spawns in the mainstem of the Russian River. Using your knowledge of the complexity of salmon life histories, morphology, and behavior, propose a plausible explanation for this pattern of run timing of different sized individuals observed in the Russian River.

Although there is still controversy over the ‘true’ relationships among Pacific salmon, many phylogenetic studies (often based on molecular genetics) indicate that sockeye, chum and pink salmon are grouped together. What morphological, life history and behavioral traits support this conclusion? What traits argue against this conclusion?

Parental care is rare among fishes. Among the species that exhibit parental care, it is often the male that provides the care. However, in Pacific salmon it is the female that invests in parental care. Provide a brief description of female parental care in salmon and discuss a plausible explanation of why it is the female and not the male that should invest in caring for the young.

While home at Thanksgiving you are asked by Aunt June, “Why do salmon come back to their home stream to spawn…it just doesn’t make sense that a salmon would swim a thousand miles up a river when there are plenty of creeks closer that they could use?” Using Tinbergen’s method of analyzing animal behavior we discussed in class, provide an answer to Aunt June that a) incorporates at least 2 proximate and b) 1 ultimate explanations for why salmon home.

Final Exam Questions Used in the Past

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Salmon embryos hatch about 20-30 cm below the surface of the gravel.Describe and explain the movement patterns that they generally display within the gravel environment.

Each of the five Pacific salmon species use estuarine habitat to some degree during their migration to the ocean. For each of the five Pacific salmon species briefly describe how much time is spent in the estuary. Why do some species spend more or less time in estuaries than others? Why do you think they spend any time at all in estuaries?

There is evidence that fine sediment is deleterious to salmon egg-to-fry survival.Describe two mechanisms by which mortality might result from high concentrations of sediment.

Salmon eggs are much larger than the eggs of other sympatric fishes.What evolutionary factors favor large eggs and what factors select for smaller eggs?

From the viewpoint of embryo survival and juvenile success, what are the factors affecting the spawning date of adult salmon?Describe the factors affecting a species of your choice.

The highest rates of mortality for naturally spawning salmon are from egg deposition to emergence.What are the sources of mortality during this period and how can salmon populations evolve to minimize such losses during incubation?

The survival of rainbow trout fry may not be independent of the date when they emerge from the gravel.Describe ecological circumstances under which survival might be highest for fry emerging early, and under which survival might be lowest for fry emerging early.

Sculpins (Cottus spp.) are generally the most abundant fishes in may Puget Sound "salmon streams".You have been hired by a local consulting company to determine whether sculpins are affecting the abundance of coho salmon.What forms of interaction would you consider, and why?

In your stream surveys and collections, you note that there seems to be an inverse relationship between the abundance of coho salmon and speckled dace.Propose two explanations for this phenomenon and devise a way to test them.

Stream-dwelling salmonids are generally territorial.Draw and explain graphs depicting the relationships between 1) number of fry emerging and territory size within a stream reach, and 2) prey abundance and territory size, given a fixed fish population.

Juvenile coho salmon generally defend feeding territories in streams but there are non-territorial "floaters" also.What are the costs and benefits of territoriality in this case?

Snorkeling observations reveal that juvenile salmonids are often associated with large pieces of woody debris.Streams that have been logged commonly have less or smaller woody debris than streams that have not been logged.However, "before and after" studies do not always reveal decreases in the abundance of these species in the streams after logging.Explain.

Imagine a lake with the following traits.20^o C water from the surface to 10 m, 10^o C from 10 m to the bottom (40 m).Most zooplankters found between the surface and 5 m. The only piscivore in the lake Salvelinus namaycush residing near the bottom.Graph the vertical distribution pattern of juvenile sockeye salmon over a 24 h period that you would expect in this lake, and justify your expectation.

The threspine stickleback (Gasterosteus aculeatus) is commonly found in lakes with sockeye salmon.You work for the state Department of Fish & Game and are charged with determining whether the sticklebacks are competing with the sockeye salmon fry.Describe the research program that you would initiate to help you address this question.

You are the management biologist for a lake which has a kokanee population.You know that they seem to selectively prey on large zooplankton species in lakes, based on the literature.Local fishermen complain that the kokanee are not as large as those in another lake and urge you to introduce a large zooplankton species found in the other lake.You are reluctant to do so, out of a vague sense that it is not wise to fool with Mother Nature but the fishermen counter that the kokanee were also introduced so who cares if there is one more introduction, if it leads to better fishing.What is your response, and why.

Sockeye salmon fry commonly move up and down in the water column on a daily basis during their period of lake residence.List two physical factors and two biological factors that affect depth distribution and diel vertical migration, and indicate the nature of the relationship between the factors and fish movement.

Juvenile salmon tend to eat the largest zooplankton available, yet the smallest salmon are at greatest risk of being eaten by predators.Why doesn't size-biased predation always favor large or small organisms?

You are managing a hatchery and need to decide when to release juvenile coho salmon as they approach "smolthood".What will be the basis of your decision?State what information you would need to base your decision and why it would be useful.Bear in mind the costs and difficulties of collecting and processing the information.That is, the most useful information under ideal circumstances might be too slow and costly to acquire and process.

Although derived from anadromous sockeye salmon, kokanee do not migrate to the ocean.Would you expect kokanee to still undergo a smolting process?Why or why not?Describe at least two techniques that would allow you to compare the smolt transformation process of kokanee and anadromous sockeye.

Smolts of most salmon species spend some time in estuaries on their way to the ocean.Provide two different hypotheses as to why salmonids have a period of estuarine residence and discuss the merits of each hypothesis.

Concerned about the poor returns to your hatchery, you consult with an internationally famous physiologist who tells you that elevated levels of thyroxine are typical of the smolt transformation period.You know a drug dealer who sells thyroid stimulating hormone for application to juvenile salmon.Under what circumstances might it benefit salmon survival?

Hargreaves and LeBrasseur placed coho salmon smolts in seawater pens with chum fry or with a mixture of pink and chum fry.Would you guess that the coho ate the larger chums, smaller ones, or no pattern?If the sizes were similar, would the coho tend to eat more pinks or chums?Justify your predictions.

Beacham and Starr studied Fraser River chum salmon and reported that males made up 54% of the 3 year olds, 44% of the 4 year olds, and 57% of the 5 year olds.Why might the sex ratio vary in this manner?Explain, for both males and females, the costs and benefits of maturing at the different ages.

Is the growth of salmon in the open ocean density dependent?Are any such effects evident within or among species?Choose examples from studies on long term trends in salmon abundance and body size, correlations between salmon abundance and size among brood years or regions, and data from large-scale releases from hatcheries.

Ricker listed eight hypotheses to explain the declining trends in age and body size of salmon in the catch.List and evaluate three of these hypotheses that specifically pertain to the effects of fishing.For each hypothesis, describe a species for which it might be most applicable.

Alternative version: Take one hypothesis, explain it fully, and propose a critical test of it.

You work for a fisheries agency and are given the job of restoring salmon runs to a section of a river above a dam.The dam cut off all salmon runs and the local genetic stocks were eliminated.The dam itself has now been removed.What would your approach be in deciding how to restore runs to the river?You must be specific about what you would do and the reasons behind your actions.

The is a widely-held belief that "hatchery fish are different from wild fish".What genetic differences might arise as a result of 1) spawning operations, and 2) rearing regimes.Describe processes operating on adults and juveniles that might cause hatchery fish to diverge genetically from their wild ancestors.

While clear-cuts may not be pleasing to look at, it has proven surprisingly difficult to document their harm to fish populations.Specifically, juvenile stream-dwelling salmonids are sometimes more abundant and/or larger after clear-cutting or in cut vs. no-cut areas.How can this be, and are the juvenile surveys sufficient to demonstrate "no harm done"?

You are the manager of a hatchery that produces chinook salmon.Each year a proportion of the males return as "jacks".Should you avoid using jacks when you spawn the females, spawn some of the jacks with all the females, all the jacks with some of the females, or what?Explain your rationale and the likely consequences of your policy on subsequent returns.

Martin Unwin and I found that the phenotypic traits of chinook salmon differ among "populations" from common ancestors found in New Zealand rivers.We proposed to study the genetic basis for this differentiation and encountered both interest and resistance from natural resource agencies and generally greater interest from power companies.Why would this line of investigation threaten some scientists or managers?

Critically evaluate the following statement, giving examples to support your position: "Salmon are generalists, not perfectly adapted for either freshwater or marine environments because they must compete in both environments with locally adapted specialists.”

NMFS has just received a petition to list a small population of chum salmon on the coast of Washington as endangered.You have been hired to determine if this stock represents an ESU, meriting protection under the Endangered Species Act.What criteria must a salmon population meet to be considered an ESU, and how would you determine if the population meets those criteria?

Despite numerous attempts to transplant Pacific salmon within their native range, very few such efforts have succeeded in establishing new self-sustaining anadromous populations.However, Pacific salmon have been succesfully introduced to such distant and diverse envirnonments as New Zealand and the Great Lakes.Explain how community structure, exploitation rates, habitat degradation, and local adaptation might affect the success or failure of transplants.

There have been many attempts to relate logging or other land-use practices to declines in adult salmon populations.Many fall into one of the following categories:1) field studies of paired watersheds (one logged and one unlogged) or "before - after" comparisons in a single watershed, and 2) laboratory studies of the effects of physical factors such as dissolved oxygen on salmon survival at a particular life history stage, based on evidence that these physical factors are associated with logging.Describe the key strengths and weakness of each scientific approach.

Salmon redds are located in diverse parts of the stream.Describe a “high quality” and a “low quality” site and then discuss the benefits and drawbacks to each kind of site.Be specific, and be careful, even good sites have drawbacks; even poor sites have advantages.

Describe the changes in morphology associated with the parr-smolt transformation, and the mechanisms of osmoregulation by salmon in freshwater and seawater.

Explain the roles of water clarity, temperature, and the distributions of prey and predators in controlling the vertical distribution of juvenile sockeye salmon.

The Gulf of Alaska seems to have more salmon feeding in it since the late 1970s than in the two decades prior to that time.Despite this abundance of salmon, there also seems to be more zooplankton out there than before, suggesting that food is not limiting.Moreover, the water seems to be warmer lately, which should facilitate growth if there is plenty of food.Nevertheless, there are correlations indicating that in years when salmon are more numerous, the average body size is smaller.How can this be?

If there were no fishing of any sort by humans, what would the effect be on the abundance of coho salmon?Please consider both the average and variation at different life history stages: adults, newly emerged fry, parr at the end of the summer, and smolts.

You are interested in the survival of juvenile salmon migrating down a river which has a population of predatory fish.These predators have fixed territories through which the salmon must pass.Will the predation rate be related to the speed of salmon migration, the distance they have to travel, both, or neither?Explain your answer.

It is obvious how fishing on adult salmon could reduce the number of fry produced in a stream (by chum salmon, for example), but how could fishing have a negative effect on egg to fry survival?Fry to smolt survival?How could fishing have a positive effect on egg to fry survival?

Take Home Essay Questions Used in 2004

In 2004 students were given a take home essay exam instead of an in class final. The vast majority of students questioned seemed to like this format better since it allowed more freedom in response and allowed students to balance their time. Follow this link to view the exam from 2004.