Effect of Slope and Headpond on Passage of American Shad and Blueback Herring through Simple Denil and Deepened Alaska Steeppass Fbhways

Ahstn1~~-Pnssngc and trnnsit time of ndult upstream-migrant Amcricnn shnd Alosu sapidissima ~ n d blucback hcrring A. ucstivalls wcrc investigated in standard Dcnil and Alnska stecppass fishways with vnrinhlc slopc and hcndpond undcr scmicontrollcd condition^. Percent of Amcricnn hhad passcd per unit time (percent pnssnge) incrcnsed with temperature, while time required to lrom the lishway entrance lo the exit (transit time) decreased with increasing temperature for both spccics. Increusing fishway slope decreased percent puSSaKe or American shad, regardless of tishwny type. Higher tishwny slope decrenscd pcrccnt pnssage or blueback herring in the sleeppass iishwny only. Low heudpond enhanced percent passage of American shad in the Denil fishwny. hut decrcnsed percent passagc of Americnn shnd in the steeppnss liuhway. Headpond lcvel had no effect on percent passage of hluebnck herring in either fishwny. Because hendpond level in thc steeppnss lishwny nffcctcd pcrccnt pnssngc of Americnri,.ghnd but not thc smnllcr hluebnck hcrring, the rchtively smnll cross-sectionnl nrca of the stccppass fishway opcrntcd at low hcndpond mny inhibil pussngc of I q c r species such as American shad. Transit time of American shad decreased with bolh incrcnsing slopc and high headpond, and American shad incrcnscd through-water swimn~inp spccd undcr these conditions. American shad appeared to regulntc their swimming speed through Dcnil-type fishways below rntlximill values. Blueback hcrring nsccndcd the fishways at speeds compnrnhlc to those of American shad. Shorter transit timcs wcrc not nssocintcd with incrcnscd pcrccnt passage. Turbulcncc and air entrainmenl may influence pcrccnt passngc of Amerioun shnd morc than longitudinnl water velocity