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1998-01-22_AgendaPacket
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1998-01-22_AgendaPacket
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Commission/Committee
Commission/Authority Name
Grass Lake WMO
Commission/Committee - Document Type
Agenda/Packet
Commission/Committee - Meeting Date
1/22/1998
Commission/Committee - Meeting Type
Regular
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Fish Surve~~s <br />The abundance and diversity of the fish community <br />can also serve as an excellent environmental indicator. <br />Surprisingly, relatively few studies have examined the <br />influence of imperviousness on fish communities in <br />headwater streams.. The results of one study is illus- <br />trated in;Figurc 6. Four similar subwatersheds in the <br />Maryland Piedmont were sampled for the number of <br />fish species present. As the level. of watershed imper- <br />viousness increased, the number of fish species col- <br />lecteddropped. Two sensitive species (trout and sculpin) <br />were lost as imperviousness increased from !0 to l2% <br />and four more were lost when impervious cover in- <br />creased to 25%. Significantly, only two species re- <br />mained in the fish community at 55% imperviousness. <br />Sensitive species, defined as those with a strong depen- <br />dence on the substrate for feeding and/or spawning, <br />showed a more precipitous decline. Klein'° found a <br />similar relationship between fish diversity and water- <br />shed imperviousness in several dozen headwater <br />streams in the Maryland Piedmont. <br />Salmonid fish species (trout and salmon) and <br />anadromous fish species appear to be most negatively <br />impacted by imperviousness. Trout have stringent <br />temperature and habitat requirements, and seldom are <br />present in mid-Atlantic watersheds where impervious- <br />ness exceeds 15%." Declines in trout spawning suc- <br />cess are evident above 10% imperviousness." In the <br />Pacific Northwest, Luchetti and Feurstenburc'x sel- <br />dom found sensitive coho salmon in watersheds hc- <br />yond 10 or IS%, imperviousness. Booth and Rcinclt' <br />noted that most urban stream reaches had poor quality <br />fish habitat when imperviousness exceeded 8 to 12%n. <br />Fish species that migrate from the ocean to spawn <br />in freshwater creeks are also very susccptihlc to im- <br />pacts of urbanization such as fish barriers, pollution, <br />flow chances, and other factors. Forexample, Limburg <br />and Schmidt" discovered that the density of anadro- <br />mous fish eggs and larvae declined sharply after a 10% <br />imperviousness threshold was surpassed in 16 <br />subwatersheds draining into the Hudson River. <br />The influence of imperviousness on other urban <br />water resources <br />Several other studies point to the strong influence <br />of imperviousness on other important aquatic systems <br />such as shellfish beds and wetlands. <br />Figure 6: Fish diversity as a function of watershed imperviousness in four subwatersheds in the <br />Maryland Piedmont (Scheeler and Galli, 1992) <br />Number of Species <br />14 <br />12 <br />70 <br />8 <br />6 <br />4 <br />2 <br />0 <br />C Sensitive Species ®Total No. of Species <br />Even relatively low levels of urban development <br />yield high levels of bacteria, derived from urban runoff <br />or failinc septic systems. These consistently high bac- <br />terial counts often result in the closure of shellfish beds <br />in coastal waters and it is not surprising, that most <br />closed shellfish beds are in close proximity to urban <br />areas. Indeed, it may be difficult to prevent shellfish <br />closure when more than one septic drain field is present <br />per seven acres-a very low urban density.' Although <br />it is widely believed that urban runoff accounts for <br />r0 <br />Numbers in brackets represent levels of <br />watershed impervlouarteaa. Sources: 7) MdDNR, 1983 2) ftdDNR, 798b 3) tCpRB, f989 <br />106 ~ Tlfi~~~a~.-tar~;i°.Liu7~~Ja~1~~,~1f~1_~-~ ~°K°~J 4,~~C~ j ~:i ~.; o a~-~ <br />Good Hope Trib. Nursery Run' Hollywood Br. Wheaton Branch <br />(Paint Branch) (NW Branch) (paint. Branch) (Sligo Creek) <br />
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