Collapse of a fish population after exposure to a synthetic estrogen
The author's study of fish gender ratios being dependent upon hormone and hormone mimmicking chemicals.  Ambient water temperature plays a role, as well.

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Metabolomic profiling reveals the intestinal toxicity of different length of microplastic fibers on zebrafish (Danio rerio)
Zebrafish larvae and adults were exposed to different length of microplastic fibers (50 ± 26 μm and 200 ± 90 μm). After exposure, microplastic fibers were observed in the gut of zebrafish even at the early life stage, causing length-dependent intestinal damage and toxicities manifested by histopathological changes and biomarker responses. Long microplastic fibers induced more serious effects. They significantly decreased the food intake of zebrafish by 54 %–67 % compared with short microplastic fibers.

T. J. Dunn, DVM, the creator of this website, has images of microscopic views of microplastic fibers embedded in various fresh water fish species, insects, and various grocery-bought food items.
SOURCE:  Fish (Bluegill) muscle	SOURCE:  Florida rain water	SOURCE:  Perch fish eggs	SOURCE: Fast food fish sandwi

Effects of microplastics on head kidney gene expression and enzymatic biomarkers in adult zebrafish
(NOTE:  Xenobiotic is a term used to describe chemical substances that are foreign to animal life and thus includes such examples as plant constituents, drugs, pesticides, cosmetics, flavorings, fragrances, food additives, caffeine, industrial chemicals and environmental pollutants.)

Due to massive production, improper use, and disposal of plastics, microplastics have become global environmental pollutants affecting both freshwater and marine ecosystems. Several studies have documented the uptake of microplastics in wild species and the correlated biological effects, such as epithelial damage, inflammation, metabolic alterations, and neurotoxicity.

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Walleye growth declines following zebra mussel and Bythotrephes invasion
Both walleye and yellow perch rely on zooplankton prey for a portion of their first year of life before switching to benthic macroinvertebrates and then fish (Wu and Culver 1992; Mittelbach and Persson 1998; Galarowicz et al. 2006). If native zooplankton become limited due to the presence of either AIS, walleye and yellow perch may switch to alternative food sources if they are large enough to make that shift (Wu and Culver 1992; Gopalan et al. 1998) or continue to persist on pelagic resources (Bremigan et al. 2003; Truemper et al. 2006). In either case, their growth may be affected. Growth of these fishes during the first year is critical to survival to later life stages, because larger individuals are less likely to succumb to size-selective predation (Nielsen 1980; Roswell 2011) and have access to a more diverse prey base (Wu and Culver 1992).

SYNOPSIS OF BIOLOGICAL DATA ON THE WALLEYE Stizostedion v. vitreum (Mitchill 1818)1/ Prepared by Peter J. Colby, Richard E. McNicol and Richard A. Ryder Fisheries Research Station Ministry of Natural Resources  http://www.fao.org/3/ap924e/ap924e.pdf

Laarman (RESEARCHER…tjd) stated that success or failure of walleye stocking appeared to depend more on the environmental and biological conditions of individual bodies of water than on the number and size of walleye that were stocked.  (This statement conflicts with local DNR activities stocking extended Growth walleyes. Let us see what the science tells us. TJD)

Page 42:  Cannibalism among walleyes has been observed in a number of lakes (Eschmeyer, 1950; Dobie, 1956; Rawson, 1957; Smith and Pycha, 1960; Fedoruk, 1966; Forney, 1968; Johnson, 1969). Titcomb (1921) observed cannibalism among hatchery reared fry as small as 13 mm long. Chevalier (1973) and Forney (1976) found cannibalism by adults on the YO? in Oneida Lake, New York to be a decisive factor in the formation of eight year classes which were followed from egg through age I. The duration of such cannibalism was influenced by the growth rate of young walleyes. Forney (1974) found that in Oneida Lake, cannibalism involving YOY walleyes decreased in years when YOY yellow perch were abundant but increased in years when YOY yellow perch were scarce. Incidence of cannibalism was seen to increase in the autumn as available perch abundance decreased. Thus, YOY yellow perch tended to act as a buffer in controlling cannibalism, and indirectly regulating walleye population size. Walleye predation regulated year class strength of yellow perch (Forney, 1971) and it is the primary source of perch mortality in communities dominated by both species (Swenson, pers. comm.). Adult walleyes have also been observed to feed occasionally on juvenile walleyes (Ryder, 1977). Winter foods consist mainly of fish (Doan, 1942; Galligan, 1960; Priegel, 1962e, 1962b) but when the availability of forage fish is limited, invertebrates beco

Walleyes 5-9 mm long, in rearing ponds, fed largely on rotifers, Keratena cochlearis, Brachionus spp., Asplanchna Sp., Euchianis sp, and Synchaeta sp.; copepod nauplii and adults and Cyclops and Diaptomus; and small cladocerans, Chydorus and Bosmina (Smith and Moyle, 1945). (This surely reflects the kinds and numbers of matrix microorganisms, aka zooplankton and phytoplankton, which should be present in the aquifer if these newly hatched walleye are to thrive.  This is great evidence that an inventory of planktonic species and numbers should be done PRIOR to stocking.  TJD) 

As the fry grew, copepods (now including Epischura) and cladocerans, including larger genera such as Daphnia and Leptodora, became the predominant food. Insects (predominantly mayfly nymphs) and fish soon become more important as the fry grow larger, until eventually fish become the predominant food (Kidd, 1927; Smith and Moyle, 1945; Smith and Pycha, 1960; Forney and Houde, 1965; Dobie, 1966a). Bulkley, Spykermann and Inmon, (1976) observed walleye fry in Clear Lake, Iowa, to feed initially upon larger zooplankters, espeaially the cladoceran Daphnia, even though rotifers and copepod nauplii were fairly abundant. Dobie (1966a) reported that when young walleyes had reached a length of 30 mm, they shifted to feeding on fish. YOY (Young Of the Year   TJD) yellow perch are the forage fish most often consumed by walleye fry (Eschmeyer, 1950; Maloney and Johnson, 1957; Dobie, 1966a; Johnson, Thomasson and Caldwell, 1966; Wolfert, 1966), although when abundant, other species have been important, especially fresh water drum and trout-perch (Priegel, 1960; 1963; 1969b), johnny darters (Raney and Lachner, 1942), spottail shiners (Smith and Pycha, 1960), and black crappies (Johnson, Thomasson and Caldwell, 1966). In Little Cutfoot Sioux Lake, Minnesota, where yellow perch are relatively unavailable because of their rapid growth rate, YOY walleyes continue feeding on invertebrates, mainly aquatic insects (Johnson, 1969).

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 1995 Behavior of larval walleye:   Phillip Warren Rieg

Cannibalism and mortality seem to occur at a greater rate at higher temperature, but for a shorter time. Further studies to develop an optimum temperature management strategy that accelerates passage of larvae through the critical periods and improves GBI and first feeding success without significantly increasing cannibalism or other mortalities may prove valuable in further development of intensive walleye larviculture.

In conclusion, we found evidence that rearing temperatures of 20°C would increase performance and viability of walleye larvae in intensive culture. Higher temperatures seem to accelerate passage through the critical period because of a greater initial activity level which improves first feeding success. Cannibalism and mortality seem to occur at a greater rate at higher temperature, but for a shorter time. Further studies to develop an optimum temperature management strategy that accelerates passage of larvae through the critical periods and improves GBI and first feeding success without significantly increasing cannibalism or other mortalities may prove valuable in further development of intensive walleye larviculture.

WALLEYE EGG PREDATION  IDENTIFYING RECRUITMENT BOTTLENECKS FOR AGE-0 WALLEYE IN NORTHERN WISCONSIN LAKES
By Hadley I. A. Boehm

Previous research has identified some species of panfish as walleye egg predators (Roseman et al. 2006), so further panfish predation studies could be conducted during the walleye egg phase.  However, a previous study of competition between walleye and smallmouth bass in their sympatric native range showed that smallmouth bass did not prey on juvenile walleye and the diet overlap between the two was not significant. On top of this, one walleye even had a smallmouth bass in its stomach (Frey et al. 2003)

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