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3.2 Aquatic Biology

Section: 3.2.1 Aquatic Resources

Section 3.2.2 Special Status Fish

Section 3.2.3 Aquatic Tissue Residues

Section 3.2.4 Toxcity Studies

3.2.1 Aquatic Resources

FISHERY RESOURCES

Fishery resources in the project area are found in four types of habitats: danals, ifrigation drains, rivers, and the Salton Sea. Flows in the New and Alamo Rivers are dominated by agricultural irrigation discharge and drainwaters and, therefore, are part of the Imperial Valley drainage system. In addition, existing canals and drain systems contain numerous sport and non-sportfishes and provide varying amounts of aquatic habitat. At least three important sportfish species are found in the saline Salton Sea that were introduced by the California Department of Fish and Game (CDFG) (Moyle, 1976).

Canals. Specific fish distribution and abundance studies are not available for the fisheries resources of the East Highline and Westside Main Canals, but it is expected that the species in these canals are similar to those known to exist in the Mi-American Canal, where sportfishes including the centrarchids (sunfishes, basses, common carp, and crappies) and ictalurids (catfishes and bullheads) have been found (lID, 1986a). Razorback suckers (Xyrauchen texanus) also are known to occur in the canals (USFWS, 1992). No fish species are endemic (native) to the canal system because it is entirely man-made. These fish species have been introduced into the region in water from the Colorado River, where they have displaced many of the fish native to that water body.

Surface Drains. At least 13 species of fish are known to inhabit the surface drains that directly discharge to the Salton Sea. Because these drains are entirely man-made, they have no native resident fish populations; the species present have been introduced with water from the Colorado River and the San Felipe Creek system, including San Sebastian Marsh and Salt Creek, the latter two which provide natural habitat for desert pupfish. Species known in the project vicinity, and that could occupy those drains that discharge directly to the sea, are shown in Table 3.2-1. Sportfish, such as green sunfish (Lepomis cyanellus), African cichilds (Tilapia mossambica and T zilli), livebearer species mollies (Poecilia and Poeciliopsis), and mosquitofish (Gambusia affinis), are commonly found in the drains adjacent to the southern Salton Sea. The state and federally endangered desert pupfish (Cyprinodon macularius) is also known to inhabit the terminus of irrigation drains that discharge directly to the Salton Sea, in addition to many tributary streams, washes, and near-shore pools. This species was listed as endangered due to habitat alteration, introduction of exotic species and contaminants, and other adverse habitat impacts. The distribution of pupfish is limited to the end of the drains by the physical nature of these drains (i.e., upstream obstructions and lack of suitable habitat).

Alamo and New Rivers. The Alamo River and the New River were not sampled during the 1991 CDFG surveys because of excessive velocity and extremely degraded near-shore substrate, cover, and water quality resulting in unsuitable habitat for the pupfish (CDFG, 1992f). Although comprehensive fish distribution and abundance surveys were not conducted on the Alamo and New Rivers, other qualitative species information is available. Fish have been sampled from these rivers for tissue residue analysis since 1978 by personnel of the California Regional Water Quality Control Board (Region 7) for the State Water Resources Control Board's (SWRCB) Toxic Substances Monitoring Program (TSMP). Fish species documented during fish tissue collections for that program are shown in Table 3.2-2. Other studies of contaminants in fish from these rivers were conducted by the Department of the Interior in 1987-1987 (Setmire et al., 1990) and 1988-1990 (Schroeder et al., 1993; Setmire et al., 1993). Species represented in that sampling were generally similar to those listed in Table 3.2-2, although sailfin mollies, redbelly tilapia, longjaw mudsuckers, and orangemouth corvina were also taken from the Alamo River delta and mudsuckers were taken from the New River delta.

Other Salton Sea Tributaries. The 1991 distribution surveys conducted by CDFG found desert pupfish in Salt Creek and San Felipe Creek. The Department of the Interior surveys (Setmire et al., 1990, 1993; Schroeder et al., 1993) also sampled mosquitofish and sailfin mollies from those creeks, as described in Section 3.2.3.

Salton Sea. Fish species inhabiting the Salton Sea are adapted to living in high-salinity waters, and most of them are non-native species (Walker, 1961; Dritschilo and Vander Pluym, 1984; Setmire et al., 1993). Pileworms are an important component of the food chains for fish in the Salton Sea, and two generalized food chains seem to be most prominent: (1) phytoplankton -> pileworm -> forage fish -> predatory fish -> fish-eating bird, and (2) a shorter chain: phytoplankton -> zooplankton -> pileworm -> water bird. Pileworms have been abundant since their introduction to the Salton Sea during the 1930s and are the principal detritus-feeding benthic organisms in the Salton Sea. The general ecology of the Salton Sea is similar to that described by Walker (1961) and summarized by Ssetmire et al. (1993).

Fish found in the Salton Sea include the sportfish sargo (Anisotremus davidsoni), orangemouth corvina (Cyhnoscion xanthulus), and Gulf croaker (Bairdiella icistia, which is also called bairdiella), and other fish species listed in Table 3.2-3. Currently sportfishing for these species is open, but there are restrictions/advisories regarding consumption. In 1986, the California Department of Health Services (DHS) issued a health advisory for sportfish because selenium concentrations in fillets of croaker (3.8 ppm wet weight), orangemouth corvina (3.6 ppm), sargo (2.1 ppm) and tilapia (1.7 ppm) exceeded or approach the DHS health advisory level of 2.0 ppm (Rasmussen et al., 1987). The advisory is also included in the health warning notices of the California Sport Fishing regulations (CDFG, 1992c). The adult public is advised, to consume no more than 4 ounces of fish every 2 weeks. Pregnant women and children are warned to avoid any fish from the Salton Sea. Fish from the Salton Sea have con-tinued to exceed the 2.0 ppm health advisory level in subsequent years (Rasmussen, 1988; Rasmussen and Starrett, 1989) demonstrating that significant bioaccumulation is currently occurring.

Even though Salton Sea fish continue to reproduce, recent data indicate significant decreases in the numbers of eggs and larvae of two important forage fish, bairdiella and sargo (Matsui, 1989). In addition to this reproductive decline, Matsui also documented deformities, predominantly retarded cephalic development in ichthyoplankton, that were attributed to ambient contamination. Such malformations have been reported previously following exposure of fish to a variety of anthropogenic contaminants, includ-ing pesticides and metals (Matsui, 1989). Selenium is known to cause deformities in fish (Lemly and Smith, 1987), and the concentration in Salton Sea bairdiella may be partially or fully responsible for the observed deformities (Setmire et al., 1993).

3.2.2 Special-Status Fish

The desert pupfish (Cyprinodon macularius) was listed as a California endangered species in 1980; the U.S. Fish and Wildlife Service (USFWS) listed this species and its critical habitat as endangered in 1986 because of habitat alteration, the introduction of exotic species and contaminants, and other habitat impacts. The desert pupfish's designated critical habitat includes San Felipe Creek, Carrizo Wash, and Fish Creek Wash in Imperial County (Federal Register, 1986). Desert pupfish habitat can also occur in pools formed by barnacle bars located in near-shore and shoreline areas ot the Satton Sea and in Salt Creek in Riverside County. Barnacle bars are deposits of barnacle shells on beaches, near-shore, and at the mouths of drains that discharge to the Salton Sea. The bars form pools that provide habitat for desert pupfish and other small fish.

Much of the natural shoreline observed during a site visit to the southern shore of the Salton Sea on February 15, 1994, was covered with a layer of this material. Some of the shoreline features in these areas are shown in Figure 3.2-1. Figure 3.2-1a shows well-defined berms composed of the shell rubble. Figure 3.2-1b shows a drain-mouth bar or spit, and Figure 3.2-1c shows a beach scarp with a beach face containing well-sorted material. Each of the features described above appears to have been formed or largely controlled by the wave climate at the site. Offshore submerged bedforms such as bars were not discernible due to poor water clarity.

Other potential fish species of concern in Imperial County are bonytail chub, (Gila elegans), Colorado squawfish, (Plychocheilus lucius), and razorback sucker (Xyrauchen texanus). These fish are listed as both federal and state endangered species, and are found in the lower Colorado River. Small numbers of the razorback suckers have been found during canal and reservoir dewaterings in the Imperial Valley over the years.

The desert pupfish is a small (<3 inches), laterally compressed, egg-laying "killifish" once commonly inhabiting desert springs, marshes, and tributary streams of the lower Gila and Colorado River drainages in California, Arizona, and Mexico. As late as 1961, 10,000 individuals were estimated to be in a single pool of the Salton Sea (Barlow, 1961, as cited by UCLA, 1983). The species is currently known from two historic locations in the United States, general Salton Sea tributaries and the Quitobaquito Spring in Pima County, Arizona (Federal Register, 1986; Lau and Boehm, 1991). They are also thought to inhabit the Rio Sonoyta and Santa Clara Slough, Sonora Mexico (Federal Register, 1986). In California, the San Felipe Creek system, including San Sebastian Marsh and Salt Creek, provide natural habitat for the desert pupfish. Ten refugia have also been established in Arizona and California with small pupfish populations. In various habitats, including irrigation drains and channels discharging to the Salton Sea, shoreline pools, natural tributaries, and the Salton Sea, desert pupfish accounted for less than 2 percent of the total catch in surveys conducted by CDFG in 1978-79 (UCLA, 1983). The San Felipe Creek population is threatened by invasion by non-native tilapia and a barrier is proposed to block tilapia migration (CDFG, 1992f).

Desert pupfish are omnivorous, feeding on detritus as well as insect larvae. They are well adapted to harsh desert environments and tolerate temperatures in excess of 43.3ūC, oxygen levels as low as 0.1 to 0.4 mg/L, and salinities nearly twice that of natural seawater (Federal Register, 1986). Desert pupfish mature rapidly, with as many as three generations a year. Spawning males defend small feeding and spawning territories in shallow (5 to 50 cm), slow-moving water with associated rooted or matted vegetation and sandy-silty substrates (UCLA, 1983). Spawning takes place between April and October when the water temperature is in excess of 20ūC (UCLA, 1983). Typical lifespan is approximately 1 to 2 years (Federal Register, 1986; UClA, 1983).

In addition to protection of the desert pupfish's remaining natural habitat, and as part of the recovery plan of the USEWS, creation of refugia populations and periodic monitoring of desert pupfish populations are required. This species of fish is also currently artificially maintained in refugia populations in captivity at various research institutions in California and Arizona and at the Dexter National Fish Hatchery in New Mexico (UCLA, 1983). Refugia populations have been established at five locations in Arizona, and at five locations in California, including populations at Salton Sea State Park and three in Anza-Borrego State Park. Additional introductions of desert pupfish populations have been made by BLM at three sites in Arizona (USFWS, 1986). CDFG has monitored desert pupfish populations and conducted habitat investigations since 1986.

The distribution of desert pupfish around the Salton Sea and the designated critical habitat for this species are shown in Figure 3.2-2 (UCLA, 1983). The locales sampled for pupfish distribution in 1991 by CDFG are shown in Figure 3.2-3 (Lau and Boehm, 1991). Of the 30 drains sampled in this area, 17 (57 percent) drains contained pupfish. Pupfish were caught in the Trifolium 13 Drain; however, this drain is no longer includ-ed in the Trifolium Interceptor project. In those studies, Vail Drains 4, 5, and 6 were found to contain desert pupfish.

In 1993, lID and CDFG conducted cooperative monitoring surveys to determine the presence and distribution of desert pupfish discharging directly to the Salton Sea and in San Felipe Wash and shoreline pools at the south end of the Salton Sea (lID, 1993a). Table 3.2-4 presents the trapping survey results, showing the numbers of each species trapped during the survey. Figure 3.2-4 shows the areas where Ill) and CDFG conducted trapping during the 1993 survey. Desert pupfish were trapped in 16 of the 29 drains surveyed and in San Felipe Wash. A total of 504 desert pupfish were trapped in this survey, compared to 161 desert pupfish trapped in 1991. Survey methods differed between the surveys, particularly in numbers of traps deployed. Trifolium 12 Drain had the greatest number of desert pupfish (261) detected in this survey. CDFG had drains retrapped where desert pupfish were not found during the initial trapping event. Trifolium 12 was included in the retrapping event to demonstrate trapping techniques and fish species present to ID operations staff. During the resurvey, only one desert pup-fish was detected in Trifolium 12 Drain. The results indicate the uncertainty that may result from trapping surveys.

Based on the trapping studies conducted to date, desert pupfish populations are known from or expected in drains directly discharging to the Salton Sea, in shoreline pools of the Salton Sea, and in desert washes at San Felipe Wash and Salt Creek. Desert pup-fish are not known to occur nor are expected in the New or Alamo Rivers because of the high sediment loads, excessive velocities, and presence of predators. Pupfish are not expected to occur in drains affected by the project that do not directly discharge to the Salton Sea. Trifolium 12 Drain is the only drain potentially affected by the pro-posed projects that discharges to the Salton Sea and is known to contain desert pupfish.

Figure 3.2-2 Distribution of Desert Pupfish and Designated Critical Habitat Around the Salton Sea
3.2-8
Figure 3.2-3 Area Sampled during the 1991 Desert Pupfish Survey
3.2.9
Table 3.2-4 1993 Desert Pupfish Trapping Survey, Page 1
3.2-10
Table 3.2-4 1993 Desert Pupfish Trapping Survey, Page 2
3.2-11
Figure 3.2-4 Area Sampled during the 1993 Desert Pupfish Survey
3.2.12

3.2.3 Aquatic Tissue Residues

SWRCB monitors the tissues of fish and other species through the TSMP. Samples of fish tissues for analysis of inorganic and organic contaminants have been taken in tj~ie Salton Sea, various drains, and in the Alamo and New Rivers since 1978. The lakst TSMP monitoring data available for fish tissues collected in the proposed project area are summarized in Table 3.2-5. Levels of selenium in Salton Sea fish are higher than those occurring in the New and Alamo Rivers, reflecting the primary source of bioaccumulation of selenium from benthic food sources of the Salton Sea. Pesticides show higher accumulation in the Alamo and New Rivers than in the drains, possibly as a result of pesticides from outside the project area.

Selenium. Selenium and other trace elements in whole fish and fillets collected from Salton Sea in 1985 also were reported by Saild (1990). Only selenium concentrations were elevated in a series of bairdiella, corvina, sargo, and Mozambique tilapia taken from the Salton Sea near the mouths of the Alamo and New Rivers. Selenium concen-trations in fillets of the Salton Sea fish were higher than those reported in fillets of freshwater fish from the Alamo, New, and Whitewater Rivers or other tributaries in the TSMIP (Rasmussen, 1988; Rasmussen and Starrett, 1989) or selenium verification study (White et al., 1987). Average selenium concentrations in fillets were between 9.0 µg/g dry weight (about 2.2 µg wet weight) in sargo and 13.4 µg/g (about 3.7 µg/g wet weight) in bairdiella; those in whole bodies were between 7.05 p.glg (~2.1 µg/g wet weight) in sargo and 10.3 µg/g (~3.2µg/g wet weight) in bairdiella.

Fish from Salton Sea and other Imperial Valley locations also were analyzed in Department of the Interior surveys (Setmire et al., 1990, 1993; Schroeder et al., 1993; see Appendix J for a description of the Department of the Interior study and other environmental monitoring programs conducted in the Imperial Valley area). In general, selenium concentrations in forage fish such as mosquitofish and sailfin mollies were 5 to 8 µg/g (chy weight) whereas those in redfin shiners and tilapia were 8 to 12 µg/g during 1986. Geographic patterns were not clear because of the limited initial sampling. During the more detailed study in 1988-1990, additional fish sampling was conducted in the Salton Sea, rivers and creeks, agricultural drains, and other locations as shown in Tables 3.2-6 and 3.2-7, as well as Figure 3.2-5. Results of selenium analyses of fish and other aquatic biota from selected locations in the vicinity of the proposed projects are summarized in Table 3.2-8 and the following paragraph(s).

Bairdiella from the S Drain Outlet had 12 to 16 µg/g (dry weight) selenium in their whole bodies; they were not sampled elsewhere (Schroeder et al., 1993, Setmire et al., 1993). Mudsuckers from the New River delta contained 6.1 µg/g selenium (whole-body, single sample). Corvina and shiners apparently were not analyzed for selenium. Mosquitofish and sailfin mollies were sampled at several locations, so they may repre-sent geographical differences in selenium exposure (Table 3.2-8). Highest selenium concentrations in both species occurred at San Felipe Creek, and in mosquitofish the second-highest concentration was at Salt Creek. In mollies, selenium concentrations also exceeded 5 µg/g at Salt Creek, Z lateral, and the 81st Street location. In both mosquitofish and mollies from New River, selenium concentrations were below 4 µg.

Table 3.2-5
Summary of Most Recent Toxic Substance Monitoring Program Fish Tissue Analysis for Contaminants for Fish Collected from Alamo River, New River, Salton Sea, andTrifolium Drain No. 7.
Contaminant	Species Collected
	Alamo River Carp	New River Channel Catfish	Salton Sea Various	Trifolium Drain No. 7 - Not Specified (1985)
Inorganics (fillets, liver, or muscle) (µg/g wet weight)
Boron -	<-6	3.3	--	5.2
Cadmium	--	<0.06	--	--
Copper	--	2.30	--	--
Mercury	--	0.29	--	1.0
Selenium	0.05 - 1.6	0.1 - 0.51	2.25 - 6.8	2.0
Zinc	--	25.0	--	--
Organics (fillets) (ng/g wet weight)
Chlordane (total)	48.9	125.9a	--	0.3
Chlorpyriphos	30	100	12	--
Dacthal	92	45	30-39	0.2
Dieldrin	90	45	--	0.3
DDT (total)	5,435b	2, 635a	5.0	--
Endosulfan (total)	50	52	--	--
Endrin	16	<15.0	--	0.3
Hexachlorobenzene	5.9	26	--	--
PCB (total)	60	340	--	2.0
Toxaphene	450a	240a	--	5.0
Chemical Group A	654.9	462.9	--	--
aExceeds NAS 1973 guidelines. bExceeds FDA 1984 action levels.
Source: Rasmussen et al., 1987; Rasmussen and Starrett, 1989; Rasmussen and Blethrow, 1991; Rasmussen, 1992

Table 3.2-6
Biological Sampling Sites for the Detailed Study of the Salton Sea Area (Locations of Sites Shown in Figure 3.2-4)
Site No.	Location	Site No.	Location
Salton Sea		Drainwater Ditches
B1	Salton Sea National Wildlife Refuge-Unit 1	B22	Trifolium 5
B2	Poe Road	B23	Trifohum 13
B3	U.S. Navy Test Base	B24	Trifolium 14
B4	Salton City	B25	Vail Cutoff
B5	Salton Sea Beach	B26	Vail 4
B6	Desert Shores	B27	Vail 4A
B7	Desert Beach	B28	Vail Drain at New River
B8	Bob's Playa River Marina	B29	S Lateral
B9	Bombay Beach	B30	Z Lateral
B1O	81st Street	B31	S Lateral Drain outlet
B11	Alamo River delta	B32	Johnson Street
B12	Red Hill Marina	Freshwater Impoundments
B13	Obsidian Butte	B33	Shady Acres Duck Club
B14	Bowles Road	B34	RH Pond
B15	New River delta	B35	HQ Pond
B16	Whitewater River delta	B36	Reidman Pond
Rivers and Creeks		B37	Hazard Pond
B17	New River at Rio Bend Imperial Valley	B38	South Brawley
B18	Alamo River at Garst Road	B39	McKendry Road
B19	San Felipe Creek
B20	Salt Creek
B21	Colorado River at Palo Verde
Source: Schroeder et al (1993).

 

Table 3.2-7 Biotic Samples Collected from Sites in the Salton Sea Study Area (Sites Described in Table 3.2-6)
Species	Sample	Sites
Vegetation
Blue-green algae	Composite	B32
Filamentous green algae	Composite	B1, B3, B4, B5, B6, B7, B8, B9, B12, B13, B14, B31
Tubular green algae	Composite	B1, B2, B3, B4, B5, B6, B7, B8, B9, B12, B13, B14, B31
Common cattail	Whole plant	B19, B20, B30, B31, B32
Periphyton	Composite	B1
Invertebrates
Asiatic river clam	Soft-tissue composite	B1, B15, B16, B17, B18, B21, B23, B24, B25, B26, B28, B30, B32
Crayfish	Whole body	B1, B11, B15, B24, B37
Pelagic invertebrate "mixture"	Composite	B1, B23
Pileworm	Composite	B1, B11, B27
Waterboatman	Composite	B11, B15, B18
Fish
Bairdiella	Whole body	BlO
Longjaw mudsucker	Whole body	B15
Mosquitofish	Whole body	B15, B19, B20, B31, B32, B37
Orangemouth corvina	Whole body	B1
Redfin shiner	Whole body	B16
Sailfin molly	Whole body	B1, B16, B17, B19, B20, B30, B31, B32, B37
Tilapia	Whole body	B1, B15, B16, B17, B22, B37
Amphibians
Bullfrog	Whole body	B18
Reptiles
Spiny softshell turtle	Fat/liver/egg	B26, B37
Birds
American coot	Liver	B15, B16, B17, B25, B37
Barn owl	Muscle	B17
Black-necked stilt	Carcass/egg	B1, B11,B15, B16, B17, B24, B25, B29, B34, B36, B37, B39
Cattle egret	Muscle	B17, B37
Double-crested cormorant	Muscle	B17, B37
Eared grebe	Liver/muscle	B13, B15
Great blue heron	Muscle	B1
Herring gull	Muscle	B37
Northern shoveler	Liver/muscle	B1,B11, B16, B33, B37
Ruddy duck	Liver/muscle	B1, B15, B17, B24, B26, B35, B37
White-faced ibis	Liver/muscle	B38
Yuma clapper rail	Carcass	B29
Notes: Samples collected at each site were not necessarily analyzed for both organic and inorganic chemicals (e.g., Asiatic river clams collected at Site B1were analyzed for organics, but not inorganics. Source: Schroeder et al. (1993)

Figure 3.4-5: U.S.Dept. of Interior Biological Sampling Sites in the Study Area: Salton Sea, Imperial Valley, and the Colorado River.  

Table 3.2-8
Summary of Selenium Concentrations (µg/g dry weight) in Selected Species of Fish from Salton Sea and Nearby Areas
Location	Mosquitofish	Sailfin molly
B15: New River Delta	3.5	na
B17: New River at Rio Rend	na	2.9
B19: San Felipe Creek	7.4	7.4
B20: Salt Creek	6.4	5.5
B30: Z Lateral	na	5.3
B31: 81st Street	4.7	5.8
B32: Johnson Street	2.6	2.5
na = Not analyzed at this location.

Selenium concentrations in algae from around the perimeter of Salton Sea were consistently less than 2 µg/g (dry weight) and did not show clear geographical patterns. Except for San Felipe Creek, selenium concentrations in cattails were below 1 µg/g. Soft tissues of Asiatic river clams were analyzed from several locations (Schroeder et al., 1993; Setmire et al., 1993). A sample of "pelagic invertebrates" from Salton Sea NWR Unit 1 (Location Bi) contained 3.1 µg/g selenium. Results for selenium in the second sample (from Location B23) were not reported. Other results for selenium are summarized in Table 3.2-9. Selenium concentrations in clams from most locations were 5 µg/g or higher, with the highest level at Trifolium 13. Pileworms from the Alamo River delta and Vail 4A contained 12 and 8 µg/g, respectively, of selenium, while those from Salton Sea NWR Unit 1 had only 2 µg/g selenium. All waterboatmen had <4µg/gselenium.  

Table 3.2-9
Summary of Selenium Concentrations (µg/g dry weight) in Selected Invertebrates from Salton Sea and Nearby Areas
Location	Asiatic River Clam	Crayfish	Pileworm	Water- boatman
B1: Salton Sea National Wildlife Refuge - Unit 1	na	na	2 (a)	na
B11: Alamo River delta	na	3.3	12	3.3
B15: New River delta	6.4	2.9	na	2a
B17: New River at Rio Rend	5.9	na	na	na
B18: Alamo River at Garst Road	5 (a)	na	na	2.6
B21: Colorado River at Palo Verde	5 (a)	na	na	na
B23: Trifolium	137 (a)	na	na	na
B24: Trifolium	145 (a)	na	na	na
B25: Vail Cutoff	5.6	na	na	na
B27: Vail 4A	na	na	8 (a)	na
B30: Z Lateral	2.9	na	na	na
B32: Johnson Street	2.6	na	na	na
aValues are the geometric mean of detected concentrations. na = Not analyzed at this location. Source: Schroeder et al. (1993).

Crayfish and Asiatic river clams had mean selenium concentrations close to background values (about 4 µg/g dry weight) found in freshwater invertebrates (Ohlendorf, 1989; Setmire et al., 1993). Selenium levels in Asiatic river clams collected from 5 drains ranged from 2.6 to 6.4 , µg/g dry weight, with a mean of 4.4 µg/g dry weight (Setmire et al., 1993). The highest selenium concentrations were detected in Asiati~ river dams taken from the New River and the Trifolium Drain (6.3 and 6.4 µg/g dry weight, respectively). Asiatic river clams from habitats affected by significant drainwater flows typically have higher selenium levels than observed in freshwater invertebrates, indicat-ing that clams bioaccumulate selenium in proportion to drainwater influence (Setmire, 1993).

Bioassay results from transplanted Asiatic river clams showed increased bioaccumulation of selenium with periods of higher drainwater flows as shown in Figure 3.2-6. Transplanted clams in the Trifolium Drain bioaccumulated selenium to levels 40 per-cent higher than initial concentrations. The increased bioaccumulation rates were observed during the peak spring irrigation period when higher drainwater flows occur. Indigenous Asiatic river clams in the Trifolium Drain had selenium concentrations of 6.3 µg/g dry weight compared to the range observed in the transplanted clams (4.4 to 7.5 µg/g dry weight) at the time of bioassay. In contrast, relatively little change was observed in selenium levels of clams obtained from the Alamo River bioassay during the initial 4 months of the study (Setmire et al., 1993).

Figure 3.2-6: Bioaccumulatlon of Selenium In Transplanted Asiatic River Clams, 1989-90
Source: Setmire et al., 1993

Boron. The highest levels of boron found in aquatic invertebrates in the Imperial Val-ley were detected in pileworms in the Salton Sea (up to 160 µg/g dry weight) (Setmire et al., 1993). A typical waterbird diet sample composed of pileworms, amphipods, and waterboatman had a concentration of 20 µg/g dry weight, which was higher than the 10 µg/g boron concentration found in waterboatman samples. The waterboatnian samples were comparable to background concentrations detected elsewhere (Setmire et al., 1993).

In a study of boron bioaccumulation, Asiatic river clams transplanted from the Color-ado River to the Alamo River and Trifolium Drain showed an initial increase in boron levels during the spring irrigation period followed by a depuration of boron (see Figure 3.2-7) (Setmire et al., 1993). As drainwater and sediment loads stabilized, boron levels declined.

Figure 3.2-7: Bioaccumulation of Boron In Tmnsplanted AsIatic River Clams
Source: Setmire et al., 1993

The highest dissolved boron concentrations detected in the Imperial Valley-Salton Sea studies was 11 mg/L. This level is lower than concentrations shown to cause chronic effects in invertebrates, but is higher than the 10 mg/L concentration considered safe (Setmire et al., 1993).

Boron concentrations in forage fish from rivers and drains were not detected at reporting limits up to 45 µg/g dry weight, however, bioaccumulation may occur at lower levels (Setmire et al., 1993). In one composite sample of mosquitofish, boron concentration of 25 µg/g dry weight was detected in the 1986 reconnaissance study (Setmire et al., 1990). This level was similar to concentrations detected in Kesterson Reservoir in 1985, but elevated when compared to samples from Stillwater Waterfowl Management Area (4.0 to 6.3 µg/g dry weight) and the San Joaquin River (2.2 to 9.8 µg/g) (Setmire et al, 1993). Other fish from the Salton Sea, such as bairdiella had boron concentra-tions in the 5.0 to 8.3 µg/g dry weight. Freshwater fish taken from rivers and drhins had boron concentrations in the same range as the Salton Sea species. There are no known standards, criteria, or effects levels for boron in fish (Setmire et al., 1993).

Boron concentrations in samples of herptofauna from river and drain sites show low levels of boron; however, the prey species of frogs (waterboatman) and turtles (saiffin molly and mosquitofish) were up to five times greater than levels observed in the herptofauna, indicating that biomagnification may be occurring (Setmire et al., 1993).

Organochlorines. Organochlorine concentrations in fish from the recent Department of the Interior studies were presented by Schoeder et al. (1993) and Setmire et al. (1993). Except for DDE, organochlorine concentrations were almost always below the detection limits (0.01 µg/g wet weight) for most chemicals (0.05 µg/g for PCBs and toxaphene). Because of its tendency to cause eggshell thinning in fish-eating birds, DDE is considered the most significant of the organochiorines found in fish from the Salton Sea vicinity. Total DDT, which is composed mostly of the persistent metabolite DDE, also can be compared to NAS (1973) guidelines (1 µg/g wet weight) and FDA (1984) action levels (5 µg/g wet weight), which are intended to protect fish and their consumers. Except for redfin shiners from the Whitewater River delta, DDE and total DDT con-centrations in fish were below those levels. DDE concentrations in mosquitofish, mollies, and tilapia (Table 3.2-10) were considerably lower than the levels reported in the TSMP (Table 3.2-5).

Table 3.2-10
Summary of p,p'-DDE Concentrations (µg/g wet weight) in Fish from Salton Sea and Nearby Areas
Location	Species
	Mosquitofish	Sailfin molly	Tilapia
B1: Salton Sea National Wildlife Refuge - Unit 1	na	0.18	0.3a
B15: Alamo River delta	0.6	na	0.23
B16: Whitewater River delta	na	0.26	0.31a
B17: New River at Rio Rend	na	0.16a	0.09a
B22: Trifolium 5	na	na	0.25
B37: Hazard Pond	0.57a	0.35	0.29a
aConcentrations are based on the geometric mean of detected concentrations. na = analyzed at this location. Source: Schroeder et al. (1993).

Aquatic invertebrates from rivers and drains had higher levels of p,p'-DDE concentrations than invertebrates in the Salton Sea (see Table 3.2-11). Crayfish and clams collected in freshwater rivers and drains had nearly eight times the levels observed in Salton Sea invertebrates (Setmire et al., 1993). High levels of DDE were observed in a composite sample of Asiatic rjver clams collected from the Vail Cutoff Drain. This sample had nearly 20 times the geometric mean of aquatic invertebrate samples, indi-cating clams are bioindicators for DDE exposure (Setmire et al., 1993). In contrast, a composite sample of clams from Wister Drain, which receives no drainwater, has no detectable concentration of DDT metabolites. In general, DDT metabolite concentrations in clams from rivers and drains ranged from about 0.16 to 0.47 µg/g dry weight.

Table 3.2-11
Summary of p,p'-DDE Concentrations (µg/g wet weight) in Biota from the Salton Sea Area, 1986-1990
		Locations
Sample Type		Salton Sea			New, Alamo, and Whitewater Rivers and Irrigation Drain
		N/DY	GM	Range	N/DV	GM	Range
Invertebrates
	Asiatic river clam	--	--	--	12/11	0.30	0.013-5.5
	Crayfish	--	--	--	4/4	.31	0.01-0.68
	Pileworm	2/2	0.04	0.03-0.04	&emdash;	--	--
	Waterboatman	5/5	0.04	0.01-0.07	--	--	--
Fish
	Bairdiella	5/5	0.10	0.08-0.12	&emdash;	&emdash;	--
	Corvina (fillet)	1/1	--	0.07	--	--	--
	Mosquitofish	--	--	--	3/3	0.58	0.54-0.61
	Redfin shiner	--	--	--	1/1	--	5.70
	Sailfin molly	--	--	--	5/5	0.21	0.14-0.35
	Tilapia	12/12	0.23	0.07/0.37	--	--	--
Amphibians and Reptiles
	Bullfrog	--	--	--	2/2	0.06	0.01-0.38
	Spiny softshell turtle (fat)	--	--	--	6/6	14.80	11.0-21.0
	Spiny softshell turtle (egg)	--	--	--	1/1	--	7.80
Note: Concentrations in micrograms per gram, wet weight; --, no data; N, number of samples collected; DV, number of samples with detectable values; GM, geometric mean (calculated using 1/2 detection limit when data set has more than 50 percent detectable values). (Setmire et al., (1993)

Results of bioaccumulation tests with clams in Imperial Valley drains showed that DDE exposure corresponded to increased drainwater flows during peak irrigation periods in late winter to early spring (see Figure 3.2-8). Exposure occurs as sediment borne DDT metabolites are transported with tailwater runoff and/or resuspended from sediment indrains and rivers (Setmire et al., 1993). Rivers were observed to have higher potential for DDT metabolite exposure than drains. A similar pattern was observed for selenium and boron. Rivers have much higher suspended sediment loads and higher sediment DDE concentration than drains (Setmire et al., 1993).

Figure 3.2-8: Concentration of Total-DDT In Transplanted Asiatic River Clams
Source: Setmire et al.,1993

Mosquitofish collected from river and drain sites in the Imperial Valley have higher mean DDE concentrations than fish collected from other locations in California and nationwide, although these levels were considered lower than those known to have direct adverse effects on fish (Setmire et al., 1993).

Organochiorine pesticide levels in saltwater sportfish (corvina, bairdiella, and tilapia) taken from the Salton Sea were generally low. Whole body bairdiella samples were low in DDT and metabolites, indicating pesticide residues may not be of concern to adult populations. Evidence suggested that ichthyoplankton populations are much more sensitive to contaminants than adults. Embryonic aberrations have been noted in earlier studies of Salton Sea fish populations (Setmire et al., 1993).

3.2.4 Toxicity Studies

Toxicity studies have been conducted on fish species that are found in the Salton Sea. Larvae of bairdielia and sargo die at 40,000 mg/L salinity (Lasker et al., 1972), adult orangemouth corvina and sargo die at 62,500 mg/L salinity (Hanson, 1970), desert pup-fish eggs fail to hatch at 70,000 mg/L (Kinne and Kinne, 1962), adult bairdiella die at 75,000 mg/L (Hanson, 1970), and juvenile desert pupfish die at 90,000 mg/L (Barlow, 1958). It would appear that 40,000 mg/L is the threshold salinity where damage to the Salton Sea's fish could begin. However, the toxicity studies referenced above were not conducted on actual Salton Sea fish populations or on fish acclimated to present Saltpn Sea salinity before being tested. Temperature, dissolved oxygen, parasitism, toxic tubstances, and other factors also may affect salinity tolerance of fish (Hagar and Garcia, 1988).

In addition to direct effects on fish, increased salinity in the Salton Sea may affect the food chain, causing other effects on the fish community (Hagar and Garcia, 1988). The upper reaches of the trophic level could be affected by salinity effects on sensitive organisms at the lowest trophic level.

Four circumstances were defined by Hagar and Garcia (1988) under which a species existence in the sea may become threatened because of increased salinity:

1. The level at which other factors interact with salinity to cause excessive mortality

2. The loss of primary food supply due to exceedance of salinity tolerance for the organism

3. Reproductive failure

4. Direct mortality due to exceedance of salinity tolerance

There is little information on circumstance 1 and 2 (Hagar and Garcia, 1988). Further increases in salinity would increase the level of risk for those species that akeady experience mortality related to environmental stress. Changes in the trophic structure of the sea are probably ongoing, and the risk that these changes will lead to significant restructuring of trophic relationships also increases with increasing salinity. For some species, the salinities at which circumstance 3 and 4 become important have been examined, though there is also a degree of uncertainty. Often the ranges are vague, and even when they are not, the importance and limits of selective forces are unknown. As conditions depart further from the present, the number of possible events expands and the ability to accurately predict them diminishes dramatically.

Hagar and Garcia (1988) provided an assessment indicating some of the more impor-tant shifts that are likely to occur as salinity increases (Table 3.2-12), but they cautioned that the assessment should be viewed as professional opinion. The assessment assumes that no new species are introduced, that corvina may be sustained past the point of reproductive failure by artificial propagation, and that no significant reproduction by any species occurs in areas outside the sea (i.e., irrigation canals). According to this assessment, pileworms would be unable . to reproduce at salinity greater than 50,000 µg/L. This would represent a loss of the existing primary food supply to fish (circumstance 2) and would represent a significant turning point for the existing fishery.

When fish populations in Salton Sea decline because of continued increases in salinity and decrease in pileworm productivity, salt-tolerant species of invertebrates would become more abundant. Examples of those invertebrates include planktonic rotifers (Brachionus plicitilis), brine shrimp (Anemia sauna), corixids (Trichocorixa reticulata), and brine flies (Ephydra spp.) (Maier et al., 1988; Parker and Knight, 1989). Although species diversities of aquatic organisms would likely be reduced as salinity increases, total abundance and biomass of invertebrates may not show a comparable reduction.

 

Table 3.2-12 Hypothetical Chronology for Salinity Effects on Salton Sea Biota
Sheet l of 2
Salinitya	Event	Probability
40	Increased importance of environmental stress on all fish	High
	Reproductive failure of bairdiella, sargo, and tilapia due to excessive salinity	Moderate
	Declining abundance of primary forage for corvina due to above with resulting lower growth rates, decreased reproduction, and higher mortality	Moderate
	Declining productivity (standing crop) of pileworms reduces food for bairdiella, young corvina	Moderate
	Changes in lower tropic levels affecting recruitment success of corvina and other fish	Low
45	Reproductive failure of bairdiella, sargo	High
	Loss of reproduction of tilapia due to excessive salinity	Moderate
	Reproduction of pileworm threatened	Moderate
	Declining productivity (standing crop) of pileworms reduces food for bairdiella, young corvina	Moderate
	Direct mortality to young and/or adult bairdiella and sargo due to excessive salinity	Moderate
	Declining abundance of primary forage for corvina due to above with resulting lower growth rates, decreased reproduction, and higher mortality	Moderate
	Loss of recruitment of corvina due to reproductive failure at upper salinity tolerance	Moderate
	Changes in lower trophic levels affecting recruitment success of corvina	Low to moderate
50	Reproduction in bairdiella and sargo no longer possible	High
	Loss of reproduction of pileworms	High
	Declining productivity (standing crop) of pileworms reduces food for bairdiella, young corvina	High
	Excedance of upper salinity tolerance for adult sargo	High
	Total loss of sargo	High
	Total loss of bairdiella	High
	Loss of recruitment of corvina due to reproductive failure at upper salinity tolerance	High
	Loss of forage for corvina, corvina fall to low numbers	High
	Loss of corvina sport fishery	High
	Reproductive failure for tilapia	Moderate to High
	T otal loss of food source for bairdiella	Moderate
	Exceedance of upper salinity tolerance for adult bairdiella	Moderate
55	Conditions intolerable for adult corvina due to lack of forage,corvina at very low numbers	Extreme
	Reproductive failure of tilapia	High
	Total loss of corvina	Moderate
	Conditions intolerable for adult corvina due to high salinity for adults	Low to Moderate

Table 3.2-12
Hypothetical Chronology for Salinity Effects on Salton Sea Biota
Sheet 2 of 2
Salinity	Event	Probability
60	Tilapia success is highiy variable from year to year due to interaction of salinity and other environmental factors	Extreme
	Corvina at very low numbers due to lack of forage, environmental stress, no reproduction	Extreme
65	Total loss of corvina	Extreme
70	Tilapia adults can no longer tolerate high salinities (regardless of other environmental factors)	High
	Reproductive failure of desert pupfish	High
	Loss of barnacle	High
	Phytoplanklon and zooplankton communities have lost some species, perhaps gained a few new ones. Species diversity is lower.No fish from previous community remain with possible exception of desert pupfish.	High
aSalinity is expressed as parts per thousand (mg/L x 103). Source: Hagar and Garcia, 1988 (modified).

3.2.5 Fish Habitat

Canals. The irrigation supply laterals and, especially, the main supply canals provide adequate fish habitat to support a fish community. The water quality and substrate of these canals can support benthic macroinvertebrates, algae, and rooted vegetation and thereby supply food for foraging fish. In some cases, velocities in these canals (especially concrete-lined canals) limit their suitability, but backwater and other slower-moving areas provide water velocities more suitable for those species, including sport-fish, that have been found in the canals.

Surface Drains. The fishery habitat in many irrigation drains in the proposed project area is of poor quality as a result of silty substrates, poor water quality, shallow water depth (or periodic drying), and lack of rooted vegetation for shade or cover. Better habitat may be found where filamentous and matforming algae provide some cover and shade. These areas are probably more frequently found where canal . (operational) discharge provides better water quality. Resident fish populations are probably highly variable due to changes in flow rate, water quality, and periodic drain maintenance.

These drains, except in areas where they are mixed with canal discharge waters or meet the near-shore pools adjacent to the Salton Sea, do not provide suitable habitat to support a well-balanced fish community. Desert pupfish have been collected from the agricultural drains entering into and connected directly to the Salton Sea (Lau and Boehm, 1991).

Alamo and New Rivers. The Alamo and New rivers provide habitat for fish as evidenced by records of fish collections. The turbidity and suspended solids resulting from drain return flow probably inhibit light penetration and increase siltation in these river channels. this unstable substrate inhibits production of benthic macroinvertebrates and attached vegetation. These factors, coupled with poor water quality from drain inputs of nutrients and agricultural pesticides, limit the suitablility of these rivers as fish habitat.

Salton Sea. The artificially created Salton Sea is an inland hypersaline lake approximately 228 feet below mean sea level. The existing salinity of greater than 44,000 mg/L TDS an summer temperatures in excess of 30ūC limit the species found in the sea. As described in Table 3.2-12, there is moderate probability for reproductive failure of bairdiells, sargo, and tilapia at 40,000 mg/L TDS along with declining productivity of bairdiella, sargo, and tilapia at 40,000 mg/L TDS along with declining productivity of pileworms, rudicing food available for bairdiella and yound corvina. Therefor, even under current conditions, fish that inhabit the Salton Sea are undergoing environmental stress.

Continuing increases in salinity and increased euktrophication will generally reduce the ability of the Salton Sea to provide appropriate and suitable habitat for most fish species, including the desert pupfish. Studies conducted for the Salton Sea Sportfish Research project indicate that Salton Sea sportsfishery is in imminent danger of collapse, as demonstrated by observed fish larval deformity and surviforship coupled with the failure of future adult reproduction (Occidental College, 1990).

Pupfish have been collected generally in the near-shore pools adjacent to the Salton Sea proper and probably exist in at least marginal habitat as long as these pools continue to form and migrate with fluctuations in the elevation of the sea (UCLA, 1983). Because pupfish prefer shallow, slow-moving waters with some vegetation for feeding and spawning habitat, these shallow Salton Sea pools probably do not provide optimal habitat (UCLA, 1983).

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