Atlantic sturgeon (Acipenser oxyrhynchus) and lake sturgeon (Acipenser fulvescens) sperm-cell morphologies were examined using scanning electron microscopy. Major differences were found in four of nine metrics, all in the head region of the cell. Atlantic sturgeon sperm cells were much shorter than those of lake sturgeon. Anterior head width exceeded posterior head width, in contrast to the arrangement in lake sturgeon sperm cells. Lake sturgeon sperm cells are nearer in size to those of other sturgeons than are Atlantic sturgeon sperm cells. Comparisons were made with sperm-cell structures known from other sturgeon species, including the Russian sturgeon (Acipenser gueldenstaedti colchicus), stellate sturgeon (Acipenser stellatus), Chinese sturgeon (Acipenser sinensis), and white sturgeon (Acipenser transmontanus). Variation in cell morphology may indicate evolutionary relationships. In addition, the fine structure of Atlantic sturgeon sperm cells was examined using transmission electron microscopy and selected metrics are described. The cell possesses a distinct acrosome, a midpiece, and a single flagellum. A comparison is made with ultrastructural details of the sperm cells of stellate and white sturgeons. Similarities among these species include radial symmetry about the longitudinal axis, an elongate shape, a distinct acrosome, and the presence of endonuclear canals. Noteworthy differences include a smaller total length and width than stellate and white sturgeon sperm cells. The main sperm-cell body is approximately 4 µm long and the flagellum about 37 µm long, resulting in a total cell length of about 41 µm. Also, the Atlantic sturgeon sperm cell possesses only two membraned endonuclear canals, in contrast to the arrangement in white and stellate sturgeons, where three such organelles are found. A structural connection of unknown function between the nuclear fossa and proximal centriole is also present in the Atlantic sturgeon sperm cell. Spermcell nuclei of white and stellate sturgeons are elongate trapezoids, with the anterior end narrower, whereas in Atlantic sturgeon the anterior portion of the trapezoid is wider than the posterior. Structural similarities between species may indicate a commonality of ancestral and evolutionary relationships that may have taxonomic implications. Ultrastructure suggests a closer evolutionary relationship between the white and stellate sturgeon than between either of these species and the Atlantic sturgeon. The present findings may be used by biologists studying the reproductive physiology, forensics, taxonomy, and genetics of sturgeons.Résumé : La morphologie des spermatozoïdes a été examinée au microscope électronique à balayage chez l'Esturgeon noir (Acipenser oxyrhynchus) et l'Esturgeon jaune (Acipenser fulvescens). Des différences importantes ont été trouvées dans quatre des neuf mesures effectuées, toutes dans la région céphalique des cellules. La longueur des spermatozoïdes est beaucoup plus courte chez l'Esturgeon noir que chez l'Esturgeon jaune. Chez l'Esturgeon ...

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Various techniques for eliminating the clumping of newly spawned walleye eggs (Stizostedion vitreum) were evaluated by measuring hatch, growth, and survival. Percent hatch was highest (83%) in egg groups water hardened in 0.01% protease solution. Other water-hardening techniques tested were: (1) continuous stirring; (2) 250 mg/L tannic acid solution; and (3) bentonire clay suspension. Low hatching percentages for eggs continuously stirred or treated with bentonire were attributed to fungus. Fungus was minimal on eggs treated with protease or tannic acid. Fish hatched from each egg treatment group were intensively cultured for 21 d in one of four rearing environments: (1) well water; (2) well water receiving 1% sea salt for the initial 3 d; (3) well water receiving a 6-mL daily addition of antifoam emulsion for the initial 9 d; or (4) well water receiving both the 1% sea salt and antifoam treatments. There was slightly higher survival in larval fish hatched from eggs treated with protease or tannic acid and reared in well water containing 1% sea salt. We observed no differences in average fish length among the test groups.

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Eggs, eleutheroembryos, and alevins of lake trout (Salvelinus namaycush) were reared in 1 of 10 levels of total gas pressure (TCP) ranging from 13 to 81 mm Hg (ΔP) above ambient barometric pressure. Rearing water was soft (30–40 mg CaCO3/L, pH 6.8), temperature was 9.3 °C, and the exogenous feeding portion of the test lasted 98 d. The supersaturation levels tested had no effect on the total survival of eggs, eleutheroembryos, or alevins, and condition factor and mean weight of fish in each treatment were statistically unchanged at the end of the study. Most of the fish that died during the feeding trial were small, had a below-average condition factor, and showed petechial hemorrhaging in the abdominal region. Length frequency distributions differed significantly among treatment groups after 56 d of feeding and remained different through 98 d. There was no difference in weight gain, condition factor, food conversion, and mortality, indicating that these measures are not useful for predicting or monitoring effects within the range of gas levels tested. The estimated incipient lowest level of effect of gas supersaturation remains unclear. A conservative recommendation of maximum supersaturation levels for small lake trout would be in the lower treatment levels used in this study.