|
<br />~' -
<br />t
<br />I~
<br />I i,.?~
<br />I ~', Bulrushes (Scirpus) and cattails '(Typha) form good stands in mail)"
<br />~ . '" places along the river as in the marshes ft Topock~ Similarly, they ma\'
<br />I'''','.''.,', be common in sloughs or seepage areas at some distance from the strea~.
<br />The cattail is an active competitor of the bulrush and is one of the first
<br />plants to establish itself on sandbarS'. ., It may' be expected to dominate
<br />~ many of the silting basins, although it in turn may be replaced by willows,
<br />~~. But few submergents were seen during the season when the river was
<br />~. visited. Ditch grass (Ruppia), the holly-leaved naiad (Najas ~arilil1),
<br />If:.' and Potamogeton were the commone~ forms observed, E,xcePt ill a few
<br />: ~reas. submergents did not appear to be abundant enough to be of mueh
<br />.,;::-=-~--.--=-,- rmpertance t&~..::-:-;- --~. ~,- ___-.:._nn.-_~-'-~-.~.--::-- .
<br />. , Only a specIes of blue-green alga seemed to be common ill the rIver.
<br />In quiet bays and sloughs this was often abundant and formed a coating
<br />on the bottom and along the shores. Green algae were alsofoun!i, and
<br />on the aprons of dams it is a common sight to see carp grazing on the
<br />"moss. "
<br />The clearing of the water has promoted the growth of aquatic plans
<br />and a continued stabilization of the river and its substratum will brin!?
<br />about an increase in both emergent and submergent vegetation. In the
<br />area around Blythe there is a striking correlation between the decrease in
<br />siltation and the increase in plant growth. There, the irrigation district
<br />has made plans to add silt to the canal water to keep down the growth of
<br />weeds. On the other hand the shifting of channels and silt movement as
<br />in areas above Imperial Dam o1iers' continued resistance to the estab-
<br />lishment of many plants, Work by the Fish and Wildlife Service on its
<br />two river refuges should haSten plant growth through seeding and the
<br />building of dikes or revetments.
<br />
<br />
<br />
<br />'138
<br />
<br />CALIFORNIA. FISH'1ND O-AME
<br />
<br />Aquatic Plant:!
<br />
<br />FIG, 65. Drowned trees In Lake Ha.vasu. May 1942,
<br />
<br />THE FISHERY OF THE LOWER COLORADO RITER
<br />
<br />Cattail btods In Haugbtelin Lake. .lan. 1942,
<br />
<br />t~~:s~;a:~ ~~s t::h~olo~rdo haveha varie~y of direct and
<br />... Th aff .'. orne, suc as N ajas, are eaten b
<br />~. , ey ord habItat to msects, snails, and oth r f od Th Y
<br />9f_refuge to young fish and rovide S . e 0 s. e'y_
<br />.at ~e roots of the bulrushes Ind cattaUawzung places. 1t-l8 --
<br />, ves~tes for the nests of sunfishes and bas:' ~h exahmPldle'ilwould
<br />'Wnal at their b 'd d . ey 0 stand
<br />~iits and algae sho~~~sb:~m ecrease bank: erosio~. S?me of the
<br />Th_c~jcontributes. fertilizing ~~~:~~so~:1~~a;~~~:na~~~t waters.
<br />.emcrease of mIcro-organisms. The larl1er a uar us pro-
<br />.,_rb, and tbus remove temporaril"- basi'" sa"'lt qth lC.plants. may
<br />plankto H J, " so' erWlSe avaIlable
<br />c.', to n, lo~ever, the abundance of these salts in the Colo-
<br />ent of hPrec u e an~ danger of material diminution The
<br />. ,. eavy vegetatIOn can of d "
<br />.imitable for fish fi h' ' course, cut Own a water area
<br />uld.be of decide~r b:n~f'toltnhgenteral, ~owever, the increase of
<br />>,~.~ _., e s ream s economy,
<br />:""':-.i..
<br />. Food
<br />
<br />=~q~ence of the several natural factors mentioned before
<br />therhand m::oubtedl:r poor along the main channel of the river'
<br />"'and cni-01ie~e a;e ahrge area~ ~uch as the lateral sloughs o~
<br />'. ., e~ s were condIhons are quite satisfacto f
<br />~'1iU.te:~o~:9-Uahc food organisms. Mo~t of these areas {iveo~
<br />" ;:mteref~c 18 more co~ pacte~ and prOVIdes a more satisfactory
<br />ft8>. h e. Orgalllc debrIS has a chance to lodge here thus
<br />"_e" .c'Ornlcdne~. t Off ten there is an establishment of all1a~ and
<br />UClve 0 ood production. '"
<br />
<br />-~------,,...-,----
<br />-._~.,;-:~
<br />
|