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Brown trout , Salmo trutta. Brook trout , Salvelinus fontinalis. Rainbow trout , Oncorhynchus mykiss. Fry, ~6 wk. Sac fry, alevin, <6 wk. Hatching. Fingerling, 6 mo. Adult 2-3 yr. Fish. Fish dominate the ______________ in most lakes, streams, rivers and estuaries.

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Brown trout , Salmo trutta


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    1. Brown trout, Salmo trutta

    2. Brook trout, Salvelinus fontinalis

    3. Rainbow trout, Oncorhynchus mykiss

    4. Fry, ~6 wk Sac fry, alevin, <6 wk Hatching Fingerling, 6 mo Adult 2-3 yr

    5. Fish Fish dominate the ______________ in most lakes, streams, rivers and estuaries. • Their large size and _________________ greatly influence the biological structure of aquatic ecosystems. • Fish occupy several different levels of the aquatic food chain • and comprise over ____________ of the earth’s vertebrate species.

    6. Fish are the main ______________ product harvested from inland waters. • _________________ recognize that fish yield is a function of the whole-lake or stream production process.

    7. Fish are almost ____________, except in mountain lakes where it is _____________ impossible for fish to pass upstream over large waterfalls that guard the lake; except when ______________ has completely changed the natural balance.

    8. Distribution and ____________ preferences Fish are masters of the turbulent water environment except for early _____________ life stages. • Fish actively _______ sites for feeding, breeding, and resting. The chemical and biological features of littoral habitats is directly correlated with • the _______ (richness) and ________ of fish species.

    9. Many lake fish show strong preferences for a habitat that includes • a diverse collection of __________ and emergent _____________. Important aspects of the submerged vegetation that attract fish include: • _______________ of the plants • density of the animal ____________ • species ____________

    10. High plant diversity supports a great diversity of _____________________ that are food for the fish. Additionally, a rich ____________ layer coating most submerged vegetation feeds small juvenile fish which use this vegetation as a refuge from ___________________.

    11. Divisions of freshwater fish groups I. Primary Groups with little or no ___________ for seawater; • lungfish, paddlefishes, pikes, minnows, catfishes, centrarchids (___________), etc. II. Secondary Groups usually ___________________ but with enough salt tolerance so that members can enter the ocean and • sometimes cross ______________________ • some gars & pikes, killifishes, live bearers (perch), cichlids.

    12. Paddlefish, Polyodon spathula

    13. Northern pike, Esox lucius

    14. Warmouth (sunfish), Lepomis gulosus

    15. Mummichog (killifish), Fundulus heteroclitus

    16. Yellow perch, Perca flavescens

    17. Blue tilapia, Tilapia aurea

    18. III. _______________ • Migratory between freshwater and the sea for purpose of _____________. ______________: diadromous fishes which spend most of their life in the sea and mature. • When fully grown they return to _____________________. ______________: diadromous fishes which spend most of their life in freshwater and go to sea as adults to breed.

    19. _________________: regularly migrating between freshwater and the sea for purposes other than breeding. • Marine: spawning in marine water, with larvae and juvenile stages briefly in freshwater (______________). • Freshwater: spawning in fresh water with larvae and juvenile stages; ____________________ before returning to freshwater.

    20. _______________ Estuarine fishes that often and freely go between marine and freshwater, • differing from above categories which usually are capable of changing mediums________________________.

    21. __________________ in freshwater fishes Freshwater fishes are ________________ to their medium • and tend to gain water by diffusion through any ______________________. If uncompensated, the inward diffusion would dilute the body fluids to the point that • the their necessary ________________ functions could no longer be accomplished. • A state referred to as “________________” • How do they compensate? • Can’t waterproof (______). • A balance must be maintained by driving the ____________.

    22. Osmoregulation The task of removing water is accomplished by the kidney. The kidneys of freshwater fish are capable of excreting urine that is more _______________________. Additional contribution to ion balance by the urinary bladder: • ____________________ of Na+ and Cl- through the wall of the bladder.

    23. Osmoregulation Although the concentration of salt in urine is low, • the _______________ causes a significant amount of salt to be lost. Salts are also lost by ____________ from the body. Losses are balanced by __________ in food and by ________ absorption through the gills.

    24. Distribution and habitat preferences Temperature and _________________ also regulate fish distribution and habitat preferences. There is a wide variety of thermal preferences both among species and __________________. • Three thermal categories are: • cold-water • cool-water • _____________ fishes __________ often prefer temperatures that are several degrees warmer than adults of the same species.

    25. Thermal preferences (cont.) These different thermal preferences act to _________________with different thermal tolerances during summer stratification. Thereby, the thermal preferences can either enhance or reduce _______________ for other resources depending on whether they __________similar species in more limited areas or separate ____________________. Although in winter, many species move to deeper water, ____________________ due to the much lower levels of activity and feeding associated with reduced _____________________.

    26. Wading shorebirds from the west coast of North America

    27. Temperature and oxygen gradients can interact to • exclude fish from all or a fraction of a water body. ________________________ • are a common problem in ________ eutrophic • warm water reservoirs and some natural lakes. The hypolimnion initially becomes _________ in summer and the ____________________ gradually rises through the season. Meanwhile, the thermocline is descending (_________________ as surface layer warms).

    28. Oxygen-temperature squeeze (cont.) Temperatures in the epilimnion and metalimnion can approach or ____________ limits, while dissolved oxygen falls below usable concentrations (__________) in the hypolimnion.

    29. Habitat preferences (cont.) Fish that are vulnerable to predation use a combination of • ____________________ to minimize their exposure to _____________ predators. • Silversides, Menidia sp., migrate from cover in littoral areas to feed in the _________________ epilimnion offshore at dawn • but return to shorelines in the morning before they are ___________. • They could fill their stomachs if they remained offshore, • but they minimize daylight exposure to offshore __________________.

    30. Menidia sp., silversides

    31. Similarly, the pelagic juvenile _______________, Oncorhynchus nerka, • stay in ______________ water during the day, • and ascend to feed for a short period in the zooplankton-rich epilimnion at _____ and dawn. • They ascend when light levels are just sufficient to __________________ • but dark enough to minimize the probability of detection by _____________. • In contrast, the older, less vulnerable kokanee feed _________ in the lighted epilimnion.

    32. Reproduction Reproductive strategies consist of reproductive traits that enable fish to leave some ________. • Reproductive traits reflect responses to environmental fluctuations. Traits that vary, include: • ___________ according to size and age • reproductive _____ • size of ________ (large eggs---larger larvae--- • mouth size, swimming capacity, sensory abilities increase with size reproductive behavior, __________ timing, ___________, the number of times spawning occurs in the life of the female (parity)

    33. Age category terminology 1. Age groups represent the number of years a fish ____________ • age group 0 = fish in ___________ of life • age group 1 = fish in second year of life. 2. ____________: fish born in 1997 are members of the 1997 year class. Fry and fingerling; variously defined, often with different meanings to different people, should not be used unless specifically defined. • ____: the time between hatching and the time at which they reach 25 mm in length • ____________: fishes between 25 mm and the length at age 1 (Piper et al., 1982).

    34. Age category terminology/Aging _________ fishes: newly hatched. • Aging methods: • scale annuli, circuli, focus • ___________

    35. Feeding Fish are often the only important large aquatic predators and results of their __________________ • Example: one small fish can eat hundreds more zooplankton than the largest predatory zooplankter. Effect of fish on zooplankton __________________

    36. Feeding may be divided among 1. pelagic fish, which feed in open water _______________(shad, herring, whitefish, minnows) or piscivorous (mosquito fish, white bass), may also eat ________________ • some feed at surface (trout, sunfish) 2. littoral, feed at ___________

    37. 3. benthic, feed on the bottom of lakes and streams. Benthic and littoral feeding is more generalized and can include: • grazing on aquatic plants (___________) • ingestion of bottom debris (_____________), • covered with ______________, protozoans, small insect larvae, and worms • ingestion of benthic invertebrates

    38. Feeding In _______________, • some fish eat _____________________ • some pluck insect larvae and crustaceans from the _____________ • some feed on _________ in pools • some seize ____________ adult insects

    39. Resource _______________ Some fish are ____________, while others are very specialized in their selection of food. This resource partitioning means that the fish eat only ______________ of the available food and thus avoid too much _________________ with others.

    40. Example: Two species of trout: _______ trout (Salvelus fontinalis) and _________ trout (Oncorhynchus mykiss) • brook feed mainly on bottom, taking chironomid and _________________ • rainbow, feed near the surface on ____________ organisms in summer

    41. Resource partitioning Another example: In streams, • the largest, most aggressive carnivores (such as trout) • pick off the ________________ • above and below __________, or near banks of submerged vegetation. • smaller fish, (such as sculpin and dace) • catch benthic invertebrates in the _______________ of the riffles • suckers ________________ at the bottom of the pools.

    42. Mottled sculpin, Cottus bairdi

    43. ___________ in flowing waters ____________ or negative, (positive) • _____________ (yes or no) • negative buoyancy is advantageous for fish that ________________ • as _________ tends to hold it in place. • many stream and river fish that live and feed on the bottom, • _______ or have reduced swimbladders. • A fish with neutral buoyancy has no __________ in water.

    44. Energy ____________: resting on bottom versus continuous swimming against current (_________) Dace have a swimbladder and continuously swim • they use _______________ than if they sat on bottom • feed largely on insect larvae taken from the bottom