CALIFORNIA DEPARTMENT OF FISH AND GAME COMMENTS TO NMFS 

REGARDING GREEN STURGEON LISTING

Executive Summary

 On December 14, 2001, in the Federal Register, the National Marine Fisheries Service 

(NMFS) published its 90-day finding that a petition to list green sturgeon (Acipenser 

medirostris) as threatened or endangered presented substantial scientific information indicating 

that the petitioned action may be warranted. As part of its status review, the NMFS solicited 

information and comments pertaining to green sturgeon. These California Department of Fish 

and Game (CDFG) comments are in response to that solicitation. 

 Our comments contain all information to which we have access concerning green sturgeon 

in California. We have made use of data from various units of CDFG and well as relevant 

published material, both primary and gray literature. We discuss green sturgeon range and 

distribution, migrations, size and age structure, habitat use, abundance, harvest, habitat impacts, 

and present and planned conservation actions. 

 For the Sacramento-San Joaquin system, we present 1) data from a tagging program of 

mostly legal-sized fish conducted intermittently since 1948; 2) fish facility salvage data from 

1968 to present; 3) trawl, gill net, fyke trap, seining, and set-line catches from surveys starting as 

early as 1980; 4) juvenile catches at the Glenn-Colusa Irrigation District diversion on the 

Sacramento River since 1988, 5) length and age data from green sturgeon collected in 1965-

1976; 6) records from green sturgeon catches by the Delta Fish and Wildlife Protection Study in 

1962-1964; and 7) records from the U.S. Fish and Wildlife Service (USFWS) of adult and 

young-of-the-year sturgeon observed in the vicinity of Red Bluff Diversion Dam on the 

Sacramento River. 

 For the Klamath River system, we present 1) seining data for adults and juveniles from the 

upper estuary from 1977 to 1990 and 2) records from CDFG and USFWS catches, observations, 

and tribal harvest calculations on the Klamath, Trinity, and Salmon rivers as early as 1968. 

 Information on the Eel River and on other coastal bays and rivers is extremely limited. On 
the Eel River, we present records and observations of CDFG personnel from as early as 1967. 

Tagging data from Arcata Bay in 1956 and 1992-1993 are presented. 

 We also comment on some of the petition’s conclusions with respect to green sturgeon in 

California, finding that a general recent (last 30-50 years) decline in green sturgeon abundance 

cannot be documented with available data; that estimated harvest rates are low (although based 

on meager data); that dams, with the exception of Red Bluff Diversion Dam and, possibly, 

Oroville Dam, may not have had much effect on available spawning habitat; and that present 

angling regulations and fishing closures provide substantial protection to green sturgeon. 

 The Interagency Ecological Program for the Sacramento-San Joaquin Estuary may provide 

more data and additional analysis for green sturgeon in the Central Valley, but this likely will not 

be available until after the March 14, 2002 deadline for submittal of comments. 
Introduction

 On June 12, 2001, the Environmental Protection Information Center, the Center for 

Biological Diversity, and WaterKeepers Northern California jointly submitted a petition to the 

National Marine Fisheries Service (NMFS) to list the green sturgeon (Acipenser medirostris) as 

either threatened or endangered under the federal Endangered Species Act (ESA). 

The petitioners justify their request based, generally, on the following assertions: 

 1) Green sturgeon have experienced a severe recent decline in overall abundance. An 

article in Fisheries, an American Fisheries Society publication, described the green 

sturgeon as endangered and indicated that it has declined 88% in most of its range. 

 2) Only two or three spawning populations remain, and probably 80-90% of all green 

sturgeon spawn in the Klamath River. More former spawning populations have been 

extirpated in the past century than currently remain in existence. The remaining 

spawning populations all occupy rivers with flow regimes affected by water projects. 

 3) The three spawning populations probably contain a few hundred mature females, at 

best and it is likely that the Klamath and Sacramento spawning populations would be 

classified as separate Evolutionarily Significant Units if adequate genetic information 

were available. 

 4) The green sturgeon may have certain unique depensatory mortality factors that take 

an increasing percentage of progressively smaller populations, dooming them to 

extinction. 

 5) Present fisheries (especially a commercial fishery in the Columbia River and 

Washington coastal region and the developing tribal gill net fishery on the Klamath 

River) continue to deplete a stock of large, old fish. It is likely that fishing pressure 

on green sturgeon has been increasing as Pacific salmon and white sturgeon 

(Acipenser transmontanus) stocks decline. 

 6) The principal fisheries for green sturgeon occur in a region with no evidence of 
4 

sturgeon spawning and, thus are exploiting fish produced elsewhere. 

 We know less about green sturgeon than any other North American sturgeon 

species and all other sturgeon species, except white sturgeon, are considered to be 

threatened in one way or another. 

 7) The sport fishery slot limit in California does not offer adequate protection to large 

and fecund female green sturgeon. 

 On December 14, 2001, the National Marine Fisheries Service (NMFS) published its 90-

day finding on the petition in the Federal Register. The NMFS found that the petition presented 

substantial scientific information indicating that the petitioned action may be warranted and will 

conduct a status review of the green sturgeon to determine if the petitioned action is warranted. 

To this end, NMFS solicited information and comments pertaining to green sturgeon. These 

California Department of Fish and Game (CDFG) comments are in response to that solicitation. 

 The comments provided here contain all information to which we have access concerning 

green sturgeon in California. We have made use of data from various units of CDFG and well as 

relevant published material, both primary and gray literature. We discuss green sturgeon range 

and distribution, migrations, size and age structure, habitat use, abundance, harvest, habitat 

impacts, and present and planned conservation actions. We also comment on some of the 

petition’s conclusions. 

 We anticipate that others with information about green sturgeon in California will respond 

to the NMFS request for comments and provide data not available to the CDFG. These include 

researchers at the University of California, Davis (UCD) (e.g., genetic differentiation of 

populations, physiology, reproductive biology), the U.S. Fish and Wildlife Service (USFWS) 

Fisheries Research Assistance Offices in Arcata and Red Bluff (e.g., Klamath River harvest, 

spawning locations, and age structure; upper Sacramento River occurrence of juveniles and 

spawning areas), and the Klamath and Trinity River tribes (harvest and size and age structure). 

Also, the Interagency Ecological Program for the Sacramento-San Joaquin Estuary may provide 

more data and additional analysis for green sturgeon in the Central Valley, but this likely will not 

be available until after the March 14, 2002 deadline for submittal of comments. 

Range, Distribution, and Migration
5 

Sacramento-San Joaquin System 

Adults

 Information on adult green sturgeon distribution and migration is available from the CDFG 

tagging program, from a CDFG telemetry study, and from incidental observations and anecdotal 

reports. 

 Tagging - Although we have discovered some tagging records for green sturgeon as early 

as 1948, the present ongoing large-scale CDFG sturgeon tagging program did not begin until 

1954, when the sport fishery reopened. It has continued intermittently since then, most recently 

by tagging in 2 successive years, skipping 2 years, then tagging again for 2 years. This pattern is 

designed to provide the most reliable estimates of mortality rates and abundance. 

 Sturgeon are captured in trammel nets in San Pablo Bay in the fall and tagged using diskdangler reward tags. Sturgeon are identified to species, measured and release location, tagger, 

date, and condition of the fish recorded. Reported recoveries of tagged fish from the fishery are 

used to determine distribution and migrations of Sacramento-San Joaquin system green sturgeon. 

 From 1954 to 2001, 233 green sturgeon have been tagged in the estuary (Table 1; 

Appendix A); 17 (7.3%) of these have been recovered, mostly from commercial fisheries (13) 

(Table 2). Two of the recoveries came from the Sacramento-San Joaquin Estuary, a fish tagged 

in 1967 and recovered over 3 years later in San Pablo Bay and a 116-cm fish tagged in 1984 and 

recovered 83 days later in San Pablo Bay. A 124-cm green sturgeon tagged in 1985 was 

recovered shortly after tagged and probably also came from the estuary. Two recoveries have 

come from the Pacific Ocean off California, one from Monterey Bay and the other from Bodega 

Head. The majority of the recovered tagged green sturgeon (12) have come from commercial 

fisheries in Oregon (7) and Washington (5). Eight of these recoveries were from the Columbia 

River (or vicinity), mostly in late summer. Three recoveries were from the vicinity of Grays 

Harbor, Washington and one was from Winchester Bay, OR. 

 In 1948 and 1949, apparently incidental to other CDFG tagging studies (probably of striped 

bass), tags of an unknown type were applied to 42 green sturgeon as small as 59 cm TL (Table 1, 

Appendix A). All except one fish captured in the Sacramento River at Broad Slough were 

caught and tagged in San Pablo Bay. Records indicate that only one of these fish was 
6 

subsequently recovered: a 65-cm fish from Monterey Bay, 197 days after being tagged (Table 2). 

 These tagging data, although sparse, indicate that legal-sized green sturgeon found in San 

Pablo Bay in the fall make extensive ocean migrations and spend much of their lives in the ocean 

or in Oregon and Washington estuaries (primarily the Columbia River and Grays Harbor 

estuaries). The recovery of one tagged fish from San Pablo Bay after 3 years at large suggests 

that some sub-adult green sturgeon remain in the Sacramento-San Joaquin Estuary for extended 

periods or move back into the estuary after years in the ocean. We know of no green sturgeon 

tagged in the Columbia River or other areas in Washington or Oregon that has been recaptured in 

California, so our knowledge of the extent of movement among these areas is based solely on 

fish tagged in the Sacramento-San Joaquin Estuary. 

 Telemetry - The CDFG attached external radio-tags to 30 sturgeon each year in 1990 and 

1991 (Schaffter 1997). These fish were captured in baited set-lines fished in the Sacramento 

River between Hood and Freeport during late winter and spring of these 2 dry years. Of the 60 

fish radio-tagged, only one was a green sturgeon. This 184-cm fish was tagged on March 7, 

1991. It was only located once, 7 days after tagging, at which time it had moved upstream to 

river kilometer (rkm) 107, above the mouth of the American River (rkm 97), but still well 

downstream of the mouth of the Feather River (rkm 128). Obviously, this one fish does not 

provide much information concerning adult green sturgeon movements in the Sacramento River. 

Incidental observations and anecdotal reports - U.S. Fish and Wildlife Service personnel 

observed sturgeon while electrofishing for winter-run chinook salmon (Oncorhynchus 

tshawytscha) below Red Bluff Diversion Dam from 1989 to 1991. Between April 3 and May 21, 

1991, they observed 19 fish identified as green sturgeon (presumably adults) (Appendix B). One 

of these was dead in shallow water and was photographed and had a pectoral fin removed. The 

accuracy of identification of the other 18 fish is unknown, but the observers were familiar with 

the differences between white and green sturgeon. The only evidence that makes these 

identifications suspect is the fact that green sturgeon were only reported in 1991; 28 fish 

observed in 1989 and 1990 were all described as white sturgeon. Numerous adult sturgeon have 

been observed in the vicinity of RBDD since 1991 by USFWS personnel (K. Brown, USFWS, 

pers. comm.) 

 In 1993, Patrick Foley (University of California, Davis [UCD]; pers. comm.) found 
7 

evidence of the occurrence of adult green sturgeon in the Feather River. This evidence was in 

the form of photographs in an area bait shop(s) and anglers’ descriptions of catching green 

sturgeon in the Feather River. Subsequent contacts by CDFG of bait shops along the Feather 

River in spring 2000 yielded no information that sturgeon had been caught in that river recently. 

Possibly, green sturgeon only use (spawn in?) the Feather River in very high flow years like 

1993 and avoid the river in low flow years (see section on spawning habitat use in the 

Sacramento-San Joaquin system). 

Juveniles

 Information on the distribution of juvenile green sturgeon is available from USFWS 

catches of young-of-the-year fish at Red Bluff Diversion Dam, catches at the Glenn-Colusa 

Irrigation District fish screens, San Francisco Bay Outflow Study otter and midwater trawl 

catches, and sampling in the estuary for juvenile sturgeon using gill nets, otter trawls, set-lines, 

and trammel nets. 

Upper Sacramento River - Larval and juvenile sturgeon have been caught in traps at two 

sites in the upper Sacramento River: below the Red Bluff Diversion Dam (RBDD) (rkm 391) and 

from the Glenn-Colusa Irrigation District (GCID) pumping plant (rkm 330). The sampling 

history extends from January 1995 through July 2000 at RBDD and from 1986 through 2001 at 

GCID. All sampling at RBDD was with rotary-screw traps. Before 1991, sampling at GCID 

was with a fyke trap and sturgeon catches were only recorded during June-August. In those 

years the fyke trap was in the bypass channel and operated only during the irrigation season. 

Starting in 1991, a rotary-screw trap was used to sample year-round (with the exception of 1998, 

when no sampling occurred) in the intake channel, where it was no longer dependent on 

diversion of water by the pumping plant; thus, sturgeon catches were recorded over a longer time 

period. 

 For purposes of these comments, we assumed that larval and post-larval sturgeon captured 

in this upper reach of the Sacramento River were green sturgeon. Although only larger 

specimens (generally >150 mm TL) have been directly identified as green sturgeon, larval fish 

from RBDD (n = 124) and GCID (n = 12) that have been grown out at the UCD to a size 

sufficient for species identification have all been identified as green sturgeon (P. Foley, UCD, in 
8 

a 1994 letter to Nick Villa, CDFG; Gaines and Martin 2001). 

 Sturgeon larvae first appear in RBDD catches from early May to early July at lengths 

ranging from 24 to 31 mm FL. Timing of peak catches has varied annually, but has always 

occurred in either June or July (Figure 1). Migration of most young-of-the-year fish past RBDD 

is over by the end of August. At this time, young-of-the-year migrants have ranged from 32 to 

70 mm FL (Gaines and Martin 2001). Sturgeon catches were highest during 1995 (as high as 

0.08 fish/acre-foot) and declined to <0.01 fish/acre-foot in 1999 and 2000 (Figure 1). Some 

green sturgeon rear to larger sizes above RBDD, or move back there after spending time 

downstream; two sturgeon between 180 and 400 mm TL were captured in the rotary-screw trap 

during 1999 (Figure 1) and green sturgeon within this size range have been impinged on diffuser 

screens associated with a fish ladder at RBDD (K. Brown, USFWS, pers. comm.). 

 Since continuous sampling started in 1991, larval and post-larval sturgeon have first 

appeared at GCID as early as May 2 (in 2001) and as late as June 25 (in 1991) (Appendix C). As 

at RBDD, catches of larvae peaked during June and July (Table 3). Some late spawning of green 

sturgeon is suggested by catches of 34-36-mm larvae in October 1997, 1999, and 2000. Larger 

juvenile sturgeon (>100 mm) have been caught in July and during fall (Appendix C). 

 Catches of sturgeon larvae at GCID from 1991 to 2001 have been highly variable, ranging 

from 23 (1994) to over 700 (1993) (Figure 2). Catch trends at GCID were similar to those at 

RBDD in some years, i.e., moderately high in 1995-1997 and low in 2000. 

San Francisco Bay Outflow Study - The Bay Study samples monthly with otter and 

midwater trawls in much of the estuary, starting in the Sacramento River above Rio Vista and in 

the San Joaquin River at Prisoners Point and going downstream through South San Francisco 

Bay. It has captured only 61 juvenile sturgeon since it started in 1980. They have ranged in size 

from 20 to 112 cm TL and have been captured throughout the estuary; however, the majority (42 

fish) have been taken from Carquinez Strait upstream through the delta (Table 4). The other 

green sturgeon came from San Pablo Bay (10 fish), and San Francisco Bay (9 fish). Most (48 

fish) juvenile green sturgeon were caught between April and October. 

Juvenile sampling - The earliest information on juvenile green sturgeon distribution in the 

estuary is from the Delta Fish and Wildlife Protection Study. These results were published in 

1966 as CDFG Fish Bulletins 133 and 136. Ganssle (1966) caught 34 juvenile green sturgeon 
9 

from 25 to 74 cm in gill nets and otter trawls in Suisun and San Pablo bays between January 

1963 and December 1994. His greatest gill net catch was in September in San Pablo Bay; otter 

trawl catches showed no pattern of distribution. 

 Similar sampling in the delta between September 1963 and August 1964 collected 138 

juvenile green sturgeon in gill nets and 28 in an otter trawl (Radtke 1966). Highest catches were 

in gill nets fished during the summer in 1-3 m of water on shoals in the lower San Joaquin River. 

Green sturgeon caught during this survey ranged from about 20 to 58 cm FL. 

 More recently, the CDFG has been sampling sturgeon from the delta downstream to San 

Pablo Bay with a variety of gear since 1988 in an attempt to assess year-class strength of white 

sturgeon. The gear has included set and drift gill nets (1988-1989), otter trawls (1989-1990) and 

baited set-lines (1991-2001). All gear was designed to target sublegal fish (<117 cm). 

 Only 20 juvenile green sturgeon have been caught in these surveys (One 169-cm adult was 

caught by set-line gear in Broad Slough in 2000.) (Table 5) and 17 of those were caught in gill 

nets when they were fished in 1988-1989. The juvenile green sturgeon ranged in size from 32 to 

122 cm and were found throughout the sampling are that started in the western delta and 

extended downstream into mid-San Pablo Bay. 

Salvage - Collection of juvenile green sturgeon at the fish facilities associated with the 

export pumps in the south delta indicates that they occur there, either naturally or as the result of 

reverse net flows in the central and south delta (Appendix D). Estimated salvage of green 

sturgeon is discussed further in other sections of these comments. 

 Also associated with water exports from the south delta are observations of green sturgeon 

in Kodiak seine catches in Clifton Court Forebay in 1992-1993. This seining was part of an 

experiment to reduce predation on young fish in Clifton Court Forebay by removing predators, 

mainly striped bass. From November 30, 1992 to March 1,1993, seining captured 42 green 

sturgeon from 42 to 185 cm FL (Appendix E). It is likely that these fish are not trapped in 

Clifton Court Forebay, but can move in and out through the radial gates at Old River when flow 

velocities through the gates are suitable. Tagging studies of striped bass in the forebay have 

shown this type movement to be common. 

Incidental Observations - Juvenile green sturgeon have been captured infrequently during 

CDFG striped bass tagging in the spring. Striped bass are captured for tagging in drift gill nets 
10 

in the western delta and in fyke traps in the Sacramento River. We have recorded sturgeon 

catches since 1989 in gill nets and since 1974 in fyke traps. Gill nets caught 20 green sturgeon in 

5 different years between 1989 and 2000; 15 of these were captured in 1 year (1994) and 14 were 

collected in April. (Appendix F). Fyke traps caught only 6 green sturgeon in 5 different years 

between 1974 and 2000. Two of these were caught before 1990, when the fyke traps were 

moved from Clarksburg to Knights Landing, and four were caught from 1990 to 2000. Four of 

the six fish were caught in April. 

 Juvenile green sturgeon <117 cm TL have been reported to be commonly caught by anglers 

in specific areas of southwestern San Pablo Bay in recent years (G. Hough, FV Morningstar 

skipper, pers. comm.) 

Klamath River System 

Adults

 The Klamath River is accessible to adult green sturgeon up to Ishi Pishi Falls (Klamath rkm 

[Krkm] 107) and green sturgeon adults have also been observed in the lower 8 km of the Salmon 

River which joins the Klamath at Krkm 106 (Moyle and Yoshiyama 1992). Spawning probably 

occurs in the immediate area of Ishi Pishi Falls, but young-of-the-year fish have not been 

confirmed upstream of Big Bar (Krkm 80) (USFWS 1998). Adult sturgeon ascend the Trinity 

River to Gray’s Falls (Trinity rkm [Trkm] 69), but no confirmation of spawning, as evidenced by 

juvenile capture, has occurred upstream of Trkm 40 (Healey 1973). 

 Mature green sturgeon usually enter the Klamath River in late March to mid-April with the 

peak migration in mid-April to mid-May. (USFWS 1982). Male:female ratios ranged from 1.1:1 

to 2.4:1 in 1980-1982 (ibid.). Most adult green sturgeon are captured during the spring salmon 

gill net fishery (April-July), but a substantial portion of the adult harvest occurs after August, 

especially in the estuary and lower 10 km of the river. 

Juveniles

 Young-of-the-year (YOY) emigration from upriver spawning areas in the Klamath-Trinity 

system, as measured by fyke nets in the Trinity River (Healey 1973) and rotary-screw traps in 
11 

the Klamath River (USFWS 1998, 1999) begins between mid-May and July. Healey (1973), 

sampling in the Trinity River at Willow Creek (Trkm 40), captured YOY green sturgeon from 

July to September, 1968. The USFWS, sampling with a rotary-screw trap at Big Bar on the 

Klamath River (Krkm 80) caught YOY green sturgeon starting from mid-May (1994) to midJune (1995-1996); catches continued through mid-July. Two juvenile sturgeon between 15 and 

20 cm long were observed in the lower 10 km of the Salmon River during October 1996 (J.B. 

Grunbaum, U.S. Forest Service, Happy Camp, CA. Memo dated Dec. 10, 1966). 

 Young-of-the-year and yearling green sturgeon are found in the upper portion of the 

Klamath River estuary. Most green sturgeon captured during CDFG seining for adult salmon 

and steelhead (Oncorhynchus mykiss) from August to early October 1984-1990 between Krkm 4 

and 6 were either YOY or age 1 fish (12-46 cm FL; see growth curve in Figure 51, USFWS 

1983). During 1984-1990, when sampling effort was recorded, catch per seine haul ranged from 

0.047 in 1984 to 0.472 in 1987 (Figure 3), suggesting that green sturgeon production in the 

Klamath River can vary annually by at least an order of magnitude. Juveniles >420 mm TL have 

not been observed upstream of tidal influence (R.A. Adair. Green sturgeon characteristics in the 

Klamath River, California. Unpublished manuscript, USFWS, Arcata, CA). 

 Immature green sturgeon between 50 and 130 cm TL and classified as coastal marine 

migrants enter the Klamath River estuary from July through November and inhabit the lower 6 

km of the river (USFWS 1985). An increasing size distribution of this population between 1979 

and 1981 led the USFWS (1982) to hypothesize that they were sampling a strong year class of 

Klamath system origin that was growing over time, implying that coastal migrants were of local 

origin. 

Eel River 

Adults

 Adult (1.5-2.0 m) green sturgeon were observed in the Eel River between rkm 100 and rkm 

160 by CDFG biologists while conducting other surveys in 1995, 1996, and 1997. In 1995, 

sturgeon were observed during April (1 fish), September (4), and November (1) and in 1996 and 

1997, during August (1 fish each year). All but one of these fish were in Humboldt County and 
12 

were legally protected from capture by the sturgeon fishery closure (Scott Downie, CDFG, pers. 

comm.). It is also felt by CDFG enforcement personnel that poaching of sturgeon is less than in 

the past because of reduced human population in this reach of the Eel River due to declines in the 

timber industry (ibid.). 

Juveniles

 Puckett (1976) reported capturing juvenile green sturgeon during a survey of juvenile 

anadromous fishes in the Eel River system from 1967 to 1970. Sampling sites included six 

locations on the mainstem between Rio Dell (rkm 20) and Dos Rios (rkm 191). The South Fork 

Eel River below Benbow Dam was not sampled. The primary sample gear was a 3.6-m-long 

funnel net of mesh graduating from 3.8 to 1.3 cm stretched measure and terminated by a live 

box. The mouth opening was attached to a 0.7 x 1.5-m pipe frame. The net was held in place by 

a bridal attached to stakes driven into the river bed, or, at two locations during higher flows, from 

bridges with a truck-mounted winch. Sampling was sporadic at most sites, but most frequent 

(although still <5 days/month) for spring through fall sampling at McCann (rkm 76) during 

1968-1970 and Fort Seward (rkm 109) during 1968 (Table 6). 

 Limited length information indicates that juvenile green sturgeon captured in May were 

<70 mm; those captured in June were 70-140 mm; and those captured in July, 80-130 mm. 

There have been no formal investigations of sturgeon in the Eel River since this study. 

 There is evidence of successful green sturgeon spawning in the Eel River during the mid1990s. Two juvenile green sturgeon, 282 mm and 510 mm FL were taken from the upper 

estuary of the Eel River in July and October 1994 (Steve Cannata, CDFG, pers. comm.). These 

lengths would correspond to age 1 and 2 green sturgeon, typical lengths found in the Klamath 

River estuary (Nakamoto and Kisanuki 1995). 

Other Coastal Rivers and Bays 

 In August 1956, Ed Best of the CDFG Marine Fisheries Division tagged 50 green sturgeon 

captured in an otter trawl in Arcata Bay (Appendix G). Green sturgeon were again tagged in 

Arcata Bay in 1992 and 1993, apparently by CDFG and Humboldt State University personnel. 
13 

In both instances, fish were probably captured in bottom trawls. We have no record of 

recaptures from any of these fish, so they provide no information on green sturgeon movements 

or distribution other than to document the apparent common occurrence of sub-adult and adult 

fish in Humboldt Bay. 

 Other evidence of green sturgeon in the Humboldt Bay system can be found in several 

reports describing the status of the species. As an example, Moyle et al. (1992) refer to several 

sources that report green sturgeon from Humboldt or Arcata Bay between the early 1970s and 

1989. 

Size and Age Structure

Sacramento-San Joaquin System 

 Information on size and age structure of green sturgeon in the Sacramento-San Joaquin 

System is available for fish captured during tagging, set-lining, gill netting, trawling, party boat 

sampling, larva sampling, striped bass tagging, and from catches at the Glenn Colusa Irrigation 

District intake and by the USFWS at Red Bluff Diversion Dam. Most of these fish were not 

aged, but age of fish captured after their first year of life can be inferred from an age-length key 

(Table 7) developed from 150 aged fish collected by a variety of methods from 1965 to 1976 

(Appendix H). Most of these fish were juveniles, so this key only includes fish up to age 9 and 

119 cm TL. The small sample size and difficulty of interpreting age of green sturgeon from 

pectoral fin ray cross sections (Three readers could seldom agree on the age of individual fish.) 

suggest that this age-length key has limited utility. Nevertheless, it can be used to assign ages to 

fish that have only been measured. 

 More recent age data from the Sacramento-San Joaquin System is not presently available, 

but fin rays were collected from 133 green sturgeon captured during tagging in 2001. These will 

be sectioned and read in 2002. 

Tagging

 We have records of the lengths of 643 green sturgeon captured during tagging since 1948 
14 

(Appendix I). From 1948 to 1954, it appears that most sturgeon captured, regardless of size, 

were measured and tagged; in 1967-1968, only legal-sized fish were measured and tagged; and 

since 1974 all fish have been measured, but only legal-sized fish have been tagged. The number 

of measured fish has varied from 5 in 1993 to 208 in 2001 and mean total length has varied from 

74.5 cm in 1994 to 126.9 cm in 1979 (Table 8). Only in 1974, 1985, and 2001 was the number 

of green sturgeon measured during tagging great enough to warrant examining the size and age 

structure - the latter with the constraint that the available age-length key includes only fish age 9 

and less and 120 cm and less and with the caveat that green sturgeon are difficult to age. 

 The size composition of the catch in these 3 years differs substantially (Figure 4) as the 

mean size increased from 80.5 cm in 1974 to 101.8 cm in 1985 and 109.5 cm in 2001. The 

differences in size composition of the catch is unlikely to be due to changes in gear, as the 

changes in mesh sizes that did occur would favor catching smaller fish in recent years. The 

trammel net was constructed using 20.3-cm stretch measure gill webbing before 1990; since 

1990 the net has been variable mesh: 1/4 15.2-cm stretch mesh, 1/4 17.8-cm stretch mesh, and 1⁄2 

20.3-cm stretch mesh. 

 The age composition of the catch was similar in 1985 and 2001, when ages 5-7 dominated 

in the size and age range for which the age-length key was applicable (Figure 5). Green sturgeon 

caught during tagging in 1974 were somewhat younger (predominantly ages 4-6) than in the 

other 2 years. These age distributions provide no strong evidence that green sturgeon produce 

strong year classes in wet years, as is the case with white sturgeon (Kohlhorst et al. 1991), but 

the high catches of year classes from the 1990s and the concentration of wet years during that 

decade suggest such a relationship may exist. 

Juvenile Surveys

Red Bluff Diversion Dam catches - Sturgeon at RBDD are sampled by the USFWS using 

rotary-screw traps intended to catch outmigrant chinook salmon. We do not have access to the 

original length data, so we cannot provide information on size-frequency distributions. 

However, the USFWS has summarized some of these data in the form of weekly mean lengths 

from 1995 to 1998 (February 9, 1999 memorandum from P. Gaines, USFWS to P. Ward, CDFG) 

and median monthly length for 1995-2000 (Gaines and Martin 2001). Unfortunately, the 1995-
15 

1998 data are described as fork length measurements (Figure 6), whereas the 1995-2000 data 

show total length (Figure 1). Hence, we do not know how these fish were measured. 

 Both sets of length date indicate that May-August period when most young sturgeon pass 

RBDD, the average size ranges from 25 to 50 mm. The weekly data (Figure 6) show that mean 

size generally increases during this period, suggesting that young sturgeon are rearing and 

growing above RBDD before moving downstream. 

Glenn-Colusa Irrigation District catches - Since 1988, CDFG personnel have recorded the 

size of young sturgeon collected in a fyke trap (1988-1990) and a rotary-screw trap (1991-2001) 

at GCID (Appendix C). Most of these fish were between 20 and 50 mm and length frequency 

distributions were similar in all years (modes between 23 and 38 mm) except 1991, when the 

mode was centered at 43 mm (Figure 7). Unfortunately, the method for measuring size 

apparently changed over time, from fork length in 1986-1993 to total length in 1996-2001; the 

length-measurement method in the intervening years - 1994-1995 - is unclear. 

 The GCID monthly length data do not show the same general increase in size over the 

sampling season as seen at RBDD (Table 3, Figure 8). Of the 8 years with sufficient monthly 

data to look at trends, only 1993 and 1997 offer the suggestion of consistent growth over time. 

The reason(s) for the difference from the growth pattern at RBDD is unknown, but may be due to 

sampling fish spawned both above and below RBDD, whereas sampling at RBDD captured only 

fish spawned above the dam. Perhaps, closure of the dam gates on May 15 results in more 

protracted spawning below the dam (only early migrant, early spawners make it above the dam) 

and continued recruitment of the smallest size class of downstream migrant sturgeon throughout 

the summer. Some late spawning of green sturgeon is suggested by catches of 34-36-mm larvae 

in October 1997, 1999, and 2000. If data were available, comparisons of length variability 

between sturgeon caught at RBDD and GCID might indicate whether a wider size range existed 

at GCID. 

 A potential problem with length data from rotary-screw traps at both RBDD and GCID is 

the efficiency for small green sturgeon of gear designed to capture juvenile chinook salmon. 

Because they sample near the surface, the traps are probably inefficient at capturing a species 

like green sturgeon that is not surface oriented. In addition, the traps may become less efficient 

as sturgeon grow and this may explain the slow apparent growth, especially at GCID. 
16 

San Francisco Bay Outflow Study - The Bay Study has captured only 61 juvenile sturgeon 

since it started in 1980 (Table 4). They have ranged in size from 20 to 112 cm TL, but fish from 

20 to 60 cm (probably mostly age 1) dominated the catch (Figure 9). 

Juvenile sampling - The earliest information on juvenile green sturgeon size distribution in 

the estuary is from the Delta Fish and Wildlife Protection Study. These results were published in 

1966 as CDFG Fish Bulletins 133 and 136. Ganssle (1966) caught 34 juvenile green sturgeon in 

gill nets and otter trawls in Suisun and San Pablo bays between January 1963 and December 

1994. In Suisun Bay, 10 of the green sturgeon were 27-35 cm and five were 40-48 cm. In San 

Pablo Bay, one fish was 25 cm and the other 18 fish were between 40 and 74 cm. Ganssle does 

not indicate whether these were fork lengths or total lengths. 

 Similar sampling in the delta between September 1963 and August 1964 collected 138 

juvenile green sturgeon in gill nets and 28 in an otter trawl (Radtke 1966). Green sturgeon caught 

during this survey ranged from about 20 to 58 cm FL (Figure 10). Most of these fish were 

probably ages 0 and 1. 

 The more recent juvenile sturgeon sampling (1988-2001) with gill nets, otter trawl, and 

baited set-lines to index year class strength of white sturgeon has caught 21 green sturgeon 

(Table 5). Except for one 169-cm TL adult and a 122-cm fish that was probably immature, all 

these were juveniles from 32 to 71 cm TL. This sample size is not large enough to draw any 

inferences about size distribution. 

Salvage - Since 1968, 86 green sturgeon have been measured at the State Fish Facilities 

and 41 have been measured at the Federal Fish Facilities (Figure 11, Appendix D). These small 

sample sizes for 33 years of salvage records make it impossible to draw any conclusions about 

annual variations in size of green sturgeon salvaged. As in other juvenile sampling in the 

estuary, most of these fish appear to be age 0 and 1. Overall, mean fork length of green sturgeon 

seen at the state facility (30.2 cm) was not significantly different than at the federal facility (32.4) 

(t = 1.02, p >0.30). 

Incidental Observations

 Green sturgeon have been incidently caught in gill nets and fyke traps used to capture 

striped bass for tagging during the spring (see Range, Distribution, and Migration). None of the 
17 

six green sturgeon caught in fyke traps were measured, but the 20 fish caught in the striped bass 

gill nets ranged in size from 42 to 108 cm TL; all but three were <71 cm (Appendix F). 

Klamath River 

 Information on growth of Klamath River green sturgeon comes from two length-age graphs, 

one compiled from sturgeon caught in 1979-1982 (Figure 12) (USFWS 1983) and the other from 

catches in 1990-1993 (Figure 13) (Nakamoto and Kisanuki 1995). All these aged fish came from 

beach seining in the Klamath River estuary and from harvest monitoring of the tribal gill net 

fishery in the lower 70 rkm of the river. Lengths of age 0 fish in the 1979-1982 age-length 

relationship (Figure 12) are a maximum of about 30 cm TL, whereas age 1 fish appear to be 

between 35 and 45 cm TL. Thus, 30 cm is about the maximum size of a age 0 green sturgeon in 

the Klamath River. 

Adults

 From 1980 to 1983, in a sample of 151 mature green sturgeon caught by gill net, seine, and 

hook and line (snagged) in the Klamath River downstream of Weitchpec (Krkm 69.7), mature 

males averaged 166.0 cm TL (s = 14.0, n = 88, range 139-207) and females averaged 189.6 cm 

TL (s = 15.1, n = 63, range 130-228) (Figure 14) (USFWS 1984). Most (90%) males were <187 

cm and most females were >171 cm. 

 Total lengths of green sturgeon harvested by the tribal fisheries on the lower Klamath River 

changed little between 1980 and 1992, the only years for which data are available (Table 9) 

(USFWS 1994). These data are not reliable as an indicator of size trends as they represent only 

catches near the mouth of the river, are only a small sample of all tribal harvest, were caught by 

different gear in some years, and seem to include some fish from USFWS beach seining in the 

early years. 

 Additional information about the size of adult and subadult green sturgeon in the river is 

available from CDFG seining for salmon and steelhead at Krkm 4 in the estuary from May 17 to 

August 1, 1977, when 48 green sturgeon from 70 to 210 cm (whether fork or total length is 

unknown) were captured (Figure 15, Appendix J). Mean length of the adult-sized fish in this 
18 

sample was 165.3 cm (s = 15.19, n = 47). 

Juveniles

 Seining and gill net catches of juvenile green sturgeon by the USFWS (1985) in 1979-1984 

from just inside the mouth of the Klamath River (Krkm 0.1) ranged in size from 30 to 130 cm TL 

(Figure 16). According to available length-age information, these fish were probably between 1 

and 15 years old. An increasing size distribution of the catch between 1979 and 1981 led the 

USFWS (1982) to hypothesize that they were sampling a strong year class of Klamath system 

origin that was growing over time, implying that these were coastal migrants of local origin that 

were re-entering the Klamath River estuary after spending time in the ocean. 

 Beach seine catches of green sturgeon by the CDFG from the upper estuary (Krkm 4 to 5), 

from August to early October, 1984-1990 were composed mostly of age 0 and 1 fish (Figure 17, 

Appendix J). These seining sites were probably upstream of the estuary mixing zone, as river 

velocity varied with the tide, but did not reverse (Hopelain 1988). 

 Healey (1973), sampling in the Trinity River near Willow Creek (Trkm 40) in 1968 found 

YOY green sturgeon ranging from 66 to 151 mm TL in July, 91 to 208 mm in August, and 173 to 

249 mm in September 1968 (Figure 18). These fish are presumed to be YOY and increased 

length over time is due to growth. Monthly mean lengths could not be calculated because original 

data are not available. 

 The USFWS (1999), fishing rotary-screw traps for salmonids at Big Bar on the Klamath 

River (Krkm 80) and Willow Creek on the Trinity River (Trkm 40) in 1996 captured YOY green 

sturgeon from 20 to about 150 mm TL (Figure 19). Catches at Big Bar suggest a prolonged 

spawning period and some growth above the trap site, whereas catches at Willow Creek suggest 

only a brief spawning period with considerable growth upstream of the trapping site. The latter is 

consistent with the interpretation of Healey’s (1973) data. 

 In culture, green sturgeon reached 74 mm 45 days after hatching (Deng 2000). This is 

consistent with growth curves that indicate that green sturgeon reach about 30 cm by the end of 

their first year. 
19 

 Eel River 

Aside from the information in Range, Distribution, and Migration, we have no data on size or age 

structure of green sturgeon in the Eel River. 

Other Coastal Rivers and Bays 

 Among these other areas, size data are available only for green sturgeon tagged in Arcata 

Bay in 1956 and 1992-1993 (Appendix G). The fish tagged in 1992-1993 were significantly 

larger (mean = 131.1 cm TL) than those tagged in 1956 (87.0 cm TL) (t = 11.41, p <0.001) 

(Figure 20). We do not know if this is a true increase in size of green sturgeon using Arcata Bay 

or an artifact of the gear used to capture the fish. We believe both groups of fish were captured 

incidental to bottom trawling by oyster growers to reduce the number of bat rays in the vicinity of 

the oyster beds. However, we presently have no information on how the trawls or fishing 

methods differed between the two collection periods. It is possible that large green sturgeon were 

more vulnerable to the fishing technique used in 1992-1993 than in 1956. 

Habitat Use

Sacramento-San Joaquin System 

Spawning

 Based on information from catches of sturgeon eggs, larvae, and juveniles in the 

Sacramento River and data on white sturgeon, it appears that green sturgeon spawn in late spring 

and early summer from above Hamilton City to above the RBDD, maybe as far upstream as 

Keswick Dam. Present knowledge about green and white sturgeon egg morphology and 

coloration, larval green sturgeon behavior, and adult distribution make it likely that eggs and 

larvae collected in previous CDFG sampling in the Sacramento River above the City of 

Sacramento have been white sturgeon and that green sturgeon are spawning upstream of the main 

white sturgeon spawning area. The evidence for this includes: 
20 

 1. No sturgeon larvae were collected in daytime sampling above Colusa in 1973 (Kohlhorst 

1976), even though the nets were fished at Ord Bend, Woodson Bridge, and Bend Bridge. If 

white sturgeon spawned above Ord Bend, larvae should have been caught at the upstream 

sampling sites. However, lack of larva catches at upstream locations during the day is consistent 

with larval green sturgeon behavior, which is distinctly negatively phototaxic. Thus, they would 

have been unlikely to be caught, even if present. 

 2. All larvae caught in 1973 were morphologically similar (except for one that was small 

and darkly pigmented) and none resembled green sturgeon larvae (D. Kohlhorst, CDFG, pers. 

comm.). 

 3. Sturgeon eggs collected on artificial substrates between Knights Landing and Princeton 

(Schaffter 1997) were similar in morphology and coloration and were not consistent with size and 

coloration of green sturgeon eggs (R. Schaffter, CDFG, pers. comm.). 

 4. Adult green sturgeon have been observed below RBDD during electrofishing surveys 

there in April and May 1991, including one dead fish for which identification was certain. 

However, a few adult white sturgeon, but no green sturgeon were observed the previous year, so 

identification of fish briefly seen in the water may be unreliable and dependent on the experience 

of the observer. 

 5. Two eggs and one larva collected at and above RBDD in early summer 2001 were 

identified genetically as green sturgeon. 

 6. The size range of YOY sturgeon (presumably green sturgeon) at both RBDD and GCID 

suggests that spawning is protracted and extends at least into early summer. The other 

explanation for small (<40 mm) fish in the river in late summer and fall is that growth is much 

slower than in the Klamath and Trinity rivers, where YOY fish at that time are more than twice 

that size. 

 7. Telemetry indicates that few white sturgeon move above Princeton during spawning 

migrations (Schaffter 1997), yet many adult sturgeon are seen in the vicinity of RBDD. 

Rearing

 Based on size and temporal distributions of young green sturgeon, it appears that many of 
21 

them rear for the first 1 or 2 months of life in the Sacramento River between Keswick Dam and 

Hamilton City (Table 3; Figures 1, 6, and 8). Capture of a few 230- to 320-cm fish from July to 

December in some years (Appendix C) suggests that a few fish may continue to reside in this area 

for their first year, or move back upstream after rearing elsewhere. 

 Catches of 1- and 2-year-old green sturgeon on the shoals in the lower San Joaquin River 

(Radtke 1966), at the fish facilities (Appendix D), and in Suisun and San Pablo bays (Ganssle 

1966 and Figure 9) indicates that some fish rear in the estuary for at least 2 years. 

 The occurrence of larger juvenile and subadult fish in San Pablo Bay and, to a lesser extent, 

Suisun Bay and the south delta (Figures 4 and 9; Appendices E, F, H, and I) is somewhat 

puzzling. Apparently these fish have returned to the estuary, possibly temporarily, after spending 

time in the ocean. The reason for their reappearance in the estuary is unknown (see following 

section on Sacramento-San Joaquin Estuary feeding). 

Feeding

 No diet analyses have been done on juvenile green sturgeon rearing in the Sacramento River 

and little work has been done on feeding of green sturgeon in the Sacramento-San Joaquin 

estuary. In the early 1960s, Ganssle (1966) found that fish (mostly 1 and 2 years old) in San 

Pablo and Suisun bays had consumed amphipods, bay and mysid shrimp, clams, annelids, crabs, 

and fish. During the same period, Radtke (1966) found that age 1 and 2 green sturgeon in the 

delta fed exclusively on amphipods and mysid shrimp. 

 It might be expected that the apparent movement of subadult green sturgeon back into the 

estuary from the ocean might be for the purpose of feeding on the abundance benthic invertebrate 

fauna. However, attempts to analyze the diet of green sturgeon in the Columbia River estuary in 

late summer have been unsuccessful because all 50+ stomachs examined were empty (T. Rien, 

Oregon Department of Wildlife and Fisheries, pers. comm.). In the Sacramento-San Joaquin 

Estuary, one green sturgeon (97 cm TL) collected during tagging in fall 2001 was examined and 

contained bay shrimp (Crangon sp.) and overbite clams (Potamocorbula amurensis) in the gut (N. 

Kogut, CDFG, pers. comm.). Gut contents of nine more green sturgeon collected during fall 2001 

tagging have not yet been examined. 
22 

Klamath River System 

Spawning

 In the Klamath River, breaching and other courtship and spawning behavior of green 

sturgeon has been repeatedly observed in a pool upstream of Orleans (Krkm 96) (Moyle et al. 

1992). Spawning probably takes place in deep, fast water (ibid). The upstream limit of sturgeon 

migration is Ishi Pishi Falls (Krkm 107), 1 km upstream of the mouth of the Salmon River, where 

juvenile green sturgeon have been observed (see Range and Distribution). In the Trinity River, 

Gray’s Falls (Trkm 69) is a barrier to upstream migration of sturgeon. Spawning must occur 

between these barriers and the Big Bar (Krkm 80) and Willow Creek (Trkm 40) trapping sites 

where larvae and YOY green sturgeon have been captured. It is not known if green sturgeon also 

spawn below these trapping sites. 

Rearing

Coastal migrants - Green sturgeon in the size range of age 3- to 15-year-old fish (Figures 16 

and 17) are commonly observed in seine catches in the saline portions of the Klamath River 

estuary, but are rarely seined in late summer and early fall in the upper, fresher portion of the 

estuary (Krkm 4-5). Thus, they probably only use the saline portion of the estuary. 

Larvae and Juveniles - As YOY green sturgeon have been found both in the Salmon River 

(see Range and Distribution) and in seine catches between rkm 4 and 5 (Figure 17) (see Size and 

Age Structure), the entire mainstem Klamath and mainstem Trinity rivers below Gray’s and Ishi 

Pishi falls, as well as an unknown portion of the Salmon River, is juvenile rearing habitat. 

Feeding

 Little information is available on green sturgeon diet or feeding behavior in the Klamath 

River system. During 1980, stomachs from nine male and seven female adult sturgeon captured 

in the Klamath River below Weitchpec were empty (USFWS 1981). 
23 

 Eel River 

 There is not enough information available from the Eel River to estimate spawning habitat 

use other than it must include some area upstream of Fort Seward (rkm 109), where YOY 

juveniles were captured in 1968, and must extend at least to rkm 160 near where adult sturgeon 

have been observed. 

 If green sturgeon in the Eel River behave similar to those in the Klamath River, the entire 

river to the estuary should be considered juvenile rearing habitat. 

 No information is available on green sturgeon diet or feeding behavior in the Eel River. 

Other Coastal Rivers and Bays 

 Not much can be said about green sturgeon habitat use in other coastal rivers and bays other 

than that they occur in some of these areas, such as Arcata Bay (see previous sections). We know 

of no data on feeding habits of green sturgeon in other coastal areas. It is possible that green 

sturgeon in Arcata Bay are feeding there, but no gut contents have been collected. 

Pacific Ocean 

 Little information is available on green sturgeon habitat use in the ocean off California. 

They have been incidently caught in commercial fisheries in nearshore areas in Monterey Bay and 

near Bodega Head (Table 2), in Tomales Bay (C. Knutson, CDFG, pers. comm.) and in the surf 

off beaches just south of San Francisco Bay (J. Klinger, Pacifica Tribune, pers. comm.). 

Abundance

Sacramento-San Joaquin System 

Tagging
24 

 Recaptures of tagged white sturgeon in the trammel nets (tagged green sturgeon have never 

been recaptured in the trammel nets) are recorded and used, in conjunction with the number 

tagged, to estimate abundance in previous years using the Petersen estimator and in the same year 

using a multiple-census technique (Ricker 1975). As no independent green sturgeon abundance 

estimate is possible with no recaptures, their abundance is estimated by multiplying white 

sturgeon abundance estimates by the ratio of green sturgeon catch to white sturgeon catch (fish 

>102 cm only) during tagging. This assumes that both species are equally vulnerable to being 

caught in the trammel net and that the movements and temporal distribution in the estuary of fish 

>102 cm of both species is similar. Neither of these assumptions likely is met; green sturgeon 

size, body shape, and shape of scutes probably affect their vulnerability to the net relative to white 

sturgeon and the migratory nature of green sturgeon suggests that a lower proportion of the 

population, especially the spawning population, is in the estuary in the fall than white sturgeon. 

Nevertheless, this is the only estimate of actual abundance available for green sturgeon in 

California. 

 The ratio of green sturgeon to white sturgeon (>102 cm) in the tagging catches has varied 

greatly over the years, from 0.002 in 1998 to 0.030 in 2001 (excluding 1994, when no green 

sturgeon >102 cm were caught) (Table 10). This variability probably has as much to do with 

sampling error in capturing the relatively rare green sturgeon as it does to actual annual changes 

in relative abundance. This is further evidence that the green sturgeon population estimates 

should be viewed with caution. 

 As an aside, and consistent with the expectation that larger green sturgeon are less likely to 

be found in the estuary in the fall when tagging takes place, the ratio of small (<102 cm) green 

sturgeon to white sturgeon in tagging catches has generally been greater than for the larger fish 

(Table 10). Ratios for these younger fish have ranged from 0.011 in 1991 and 1993 to 1.661 in 

1974. 

 Green sturgeon abundance estimates have varied substantially in the Sacramento-San 

Joaquin Estuary (Table 10). Aside from the high estimated abundance in 2001 of 3,580 fish 

(based on September and October catches only, to be comparable with estimates in earlier years), 

the largest estimate was 1,906 in 1979 and the lowest was 198 in 1954. Even without the low 
25 

estimate in 1954 and the high estimate in 2001, there is no trend in these data (F1,10 = 1.49, p 

>0.25), so they provide no evidence for a green sturgeon population decline in the SacramentoSan Joaquin Estuary. Continued high green sturgeon tagging catch and estimated abundance in 

2002 would be consistent with the production of strong year classes in the wet years of the 1990s 

and, possibly, the benefits of current operation of Red Bluff Diversion Dam. 

Juvenile Surveys

 Juvenile monitoring surveys designed to index year class strength, as well as incidental 

catches of larval or juvenile sturgeon in monitoring programs for other species provide 

information on green sturgeon abundance trends. 

Juvenile sturgeon monitoring - Over the years, this has included use of gill nets, otter trawls, 

and most recently baited set-lines to capture juvenile sturgeon (generally 2-7 years old). These 

sampling techniques are described in the previous section on the range and distribution of juvenile 

green sturgeon in the Sacramento-San Joaquin System. 

 Only 21 green sturgeon have been captured during this sampling (Table 5). Most of the 

juveniles (16) were captured in gill nets when that gear was fished from 1988 to 1990. An otter 

trawl caught one juvenile in 1989 and the set-lines caught two juveniles and two older fish in 

1998 and 2000. The higher catches in the early years of this survey are probably the result of 

greater green sturgeon vulnerability to the gill nets used then than to any decrease in abundance 

after 1990. Thus, the small sample size and change in fishing gear make it impossible to infer 

trends in juvenile green sturgeon abundance from these data. 

San Francisco Bay Outflow Study - This monitoring program has only caught 61 green 

sturgeon, all juveniles, since its inception in 1980 (Figure 21, Appendix K). Highest catch (10 

fish) was in the first year and varied between 0 and 9 thereafter. Annual catches did not exhibit a 

statistically significant time trend (F1,20 = 2.97, p = 0.10). Monthly catches were too low to 

ascertain seasonal trends in abundance. 

 For comparison, the Bay Study has caught 886 white sturgeon, for an overall ratio of 0.069 

green sturgeon:1 white sturgeon. This ratio has varied from 0 in 4 years when no green sturgeon 

were caught to 0.600 in 1994 (Figure 22, Appendix K). 
26 

Salvage - State water exports from the south delta began in 1968 and the first green sturgeon 

were seen at the state fish facilities in March of that year, when 12 fish were estimated to have 

been salvaged (Appendix L). Estimated salvage per 1000 acre-feet (TAF) of water exported was 

high in many of the years from the early 1970s to the early 1980s and reached a peak of 3.9 green 

sturgeon/TAF in 1974 (Figure 23). That was by far the highest estimated salvage per effort at the 

state fish facilities. From the late 1980s to the present, estimated green sturgeon salvage/TAF has 

been consistently low, ranging only from 0 to 0.081. The trend in estimated green sturgeon 

salvage/TAF is not statistically significant (F1,32 = 2.53, p >0.10), even though highest catches 

were in the early years of state fish facilities operation. 

 Federal exports from the delta began in 1951, but no green sturgeon were recorded at the 

federal fish facility until March 1981, when it was estimated that 75 green sturgeon were salvaged 

(Appendix L). Federal fish facility estimated green sturgeon salvage/TAF was highest in the mid1980s and reached a peak of 0.653 in 1983 (Figure 23). Like the state fish facility, estimated 

salvage at the federal facility was low from the late 1980s to the present; the range was only 0 to 

0.096. The decreasing trend in estimated salvage from 1981 to 2001 was statistically significant 

(F1,19 = 10.61, p <0.01). 

 As previously described, salvage monitoring at the state and federal fish facilities in the 

south delta at times has been plagued by problems with species identification. This is exemplified 

by the lack of green sturgeon identified at the federal facility until 30 years after export pumping 

began. An additional source of error is that the salvage estimates commonly are based on 

expansion of brief counting periods to several hours of operations. Thus, a few fish recorded in a 

5-minute count could be expanded to several hundred fish over the several-hour period 

represented by the 5-minute count. These two factors may account for the sporadic occurrence of 

green sturgeon in the salvage data and the high variability among months and years (Appendix L). 

The original salvage data is available from an FTP server found under “Fish Salvage Monitoring” 

on the CDFG Central Valley Bay-Delta Branch website (www.delta.dfg.ca.gov). 

Klamath River System 
27 

 There are no population estimates available for adult green sturgeon in the Klamath River. 

Although adult harvest has declined significantly over time (see Harvest section and Table 11), 

fishing effort has not been constant over time and fishing days have been regulated in response 

changing salmonid populations in the system. Another factor which may affect harvest efficiency 

is river flow during the primary spring fishery. These factors have not been analyzed in reports 

by the USFWS with regard to their impact on sturgeon harvest. We do not have data to assess 

changes in harvest as an indicator of adult population trends, but this could be a fruitful avenue of 

investigation. 

 California Department of Fish and Game beach seine catches per unit effort of juvenile 

green sturgeon between 1984 and 1990 varied from 0.047 in 1984 to 0.472 in 1987 (Figure 3), 

suggesting that green sturgeon production in the Klamath River can vary annually by at least an 

order of magnitude. Lengths of these fish are described in Size and Age Structure. 

 Eel River 

 The low number of adult green sturgeon observed in the Eel River (see Range and 

Distribution) suggests that adult abundance is low and that adults may not enter the river every 

year. There has been no known sampling for small fish within the river upstream of the estuary 

since 1970. 

Other Coastal Rivers and Bays 

 We know of no estimates or indices of green sturgeon abundance in other coastal rivers and 

bays in California or any information about green sturgeon population trends in these areas. 

Green sturgeon are at least intermittently common in Arcata Bay, as evidenced by the capture in 

bottom trawls of 49 fish in only 2 days in 1956 and 72 fish in 7 days in 1992 (Appendix G). 

Records of green sturgeon in other coastal areas are so infrequent that they suggest that they are 

rare in most other areas. 
28 

Harvest

Sacramento-San Joaquin System 

 Tag returns by fishers during the first year after tagging are used to estimate annual harvest 

rate. Since 1967, all sturgeon tags have offered a reward to fishers returning them. This reward 

has increased over time, from $5 initially to up to $100 at present, so it is likely that most 

recovered tagged green sturgeon are reported to us. This becomes even more likely when one 

considers the “curiosity factor” that results when a fisher encounters an unusual event, such as the 

catch of a tagged green sturgeon. 

 Because relatively few green sturgeon are tagged and even fewer are reported recaptured, 

estimated harvest rate for most tagging years is zero (Table 12). The exceptions to this are 1948, 

1979, 1984, and 1985, when 1, 2, 1, and 1 tags were reported recaptured during the first year after 

tagging and estimated harvest rates for each of these years were 0.028, 0.077, 0.042, and 0.053. 

Combining all years of tagging (except 2001, for which first-year returns are not complete), the 

estimated “average” harvest rate is 0.022 and the 95% confidence interval (assuming that tag 

return data follow the Poisson distribution - a rare and random event) is 0.009-0.048. These 

harvest rates are all similar or lower than rates considered to be adequate for maintaining the 

white sturgeon in the estuary (Kohlhorst et al. 1991). 

 The actual number of green sturgeon harvested from the Sacramento-San Joaquin 

population is more difficult to determine because it is likely that many of the fish using or 

spawning in the system are not available for tagging in the fall; they are in the ocean. Multiplying 

annual green sturgeon population estimates by the harvest rates yields minimum harvest numbers 

of 147, 46, and 45 for 1979, 1984, and 1985 (Table 12). No estimate can be made for 1948 

because no population estimate is available that year. 

Klamath River System 

 Numerical harvest estimates from 1980 to 1999 have been compiled by the USFWS for 
29 

tribal catches on the Klamath River below Weitchpec and the lower 26 km of the Trinity River. 

These statistics are included as Appendix 2 of the listing petition and reproduced here as Table 

11. Partial comparison with the source material (USFWS 1981, 1982, 1983, 1988, 1989, 1992, 

1994) indicates that the information in Table 11 is generally accurate, with one exception: all fish 

listed in the “poached” column have also been included in the Yurok harvest column (USFWS 

1981, 1982, 1983). This hook and line (snag) fishery on tribal land at Coon Creek was included 

in Yurok statistics even though “many (of the fish) were caught by non-Indians” (USFWS 

1981:86). There have been other unexplained revisions and corrections of Klamath harvest data 

during the 1980s, but other changes are minor (USFWS 1994). Estimated harvest in 1980 and 

1981 was substantially higher than in other years, but even without those years, the decreasing 

trend in harvest is statistically significant (F1,16 = 6.18, p <0.05). These data do not account for 

effort, so trend in catch per effort is unknown and may be different than for the data that is 

uncorrected for effort. 

 Legal sport catches of green sturgeon were observed at Bluff Creek on the Klamath River 

(Krkm 78) before the sport fishery was closed in 1994, but the extent of this fishery and catch is 

unknown (USFWS 1982). 

Eel River 

 No estimates of harvest or harvest rate are available from the Eel River. Most of the Eel 

River system is in Humboldt County and thus is closed to harvest of sturgeon, so there is no legal 

harvest at present. 

Other Coastal Rivers and Bays 

 No estimates of harvest or harvest rate are available for other coastal rivers or bays. 

However, some catch of green sturgeon does occur in these areas, as evidenced by the report of 

two green sturgeon captured by halibut gear in Tomales Bay in August 1993 (Knutson, CDFG, 

pers. comm.), over 20 fish (including several that were legal sized) in the surf off Pacifica on one 
30 

day in May 1995 (J. Klinger, Pacifica Tribune, pers. comm.) and trawl catches in Arcata Bay 

(Appendix G). Commercial catches in the ocean and bays may result is some mortality even 

though green sturgeon are not the target of these fishing efforts and must be released. 

Habitat Impacts

Sacramento-San Joaquin System 

 Major historical changes that likely have negatively impacted green sturgeon have occurred 

in the Sacramento-San Joaquin system, including construction of dams on almost all rivers, filling 

of the bays, altered hydrology, diversions from the rivers, and water exports from the delta. 

These and other historical habitat alterations are adequately covered in the listing petition and will 

not be further discussed here. Instead, we will deal with future activities that have the potential to 

impact green sturgeon habitat. 

Additional Upstream Water Development

 As part of the CALFED process to provide additional and more reliable water supplies 

while also improving conditions for fish and wildlife in the estuary and its tributaries, increased 

water storage in the Sacramento River basin has been proposed. This could take the form of 

raising Shasta Dam to impound more water or to store water in a pumped offstream storage 

reservoir(s) on the west side of the valley. Both of these actions have the potential to 

detrimentally affect green sturgeon habitat by altering the hydrology of the river above Hamilton 

City. Specifically, flows could be reduced downstream of Keswick or below the intake for the 

pumped storage during part of the period of upstream migration of adults. Flow may be a prime 

cue for upstream migration and spawning (Kohlhorst et al. 1991). Enlarged Shasta may also offer 

benefits to green sturgeon through higher flows and cooler temperatures during the summer 

incubation and rearing period. The extent of detriment or benefit will obviously depend on the 

manner and timing of storage and release of additional water. 
31 

Red Bluff Diversion Dam

 The operation of RBDD may be modified to better assist passage of adult salmon upstream 

and juvenile salmon downstream, with consideration also given to sturgeon passage. Essentially, 

the alternatives being considered are: 1) gates open from September 1 to June 30 (10 months), 2) 

gates open year-round (12 months), 3) continue current operation of gates open from September 

15 to May 15 (8 months). Additionally, improvements to the fish ladders are being considered 

that may result in upstream passage of sturgeon. All of these alternatives benefit green sturgeon 

by providing better access to spawning habitat above the dam, even continuation of present 

operations, which has been shown to result in substantial spawning upstream of the dam. 

Increasing the period when the dam gates are raised will reduce an impediment to downstream 

movement of juveniles. Improvements to the fish ladders may also be a benefit if they can be 

designed to emulate the north ladder on Bonneville Dam on the Columbia River, which passes 

sturgeon successfully. 

Glenn-Colusa Irrigation District

 To improve the efficiency of the GCID diversion by providing higher water levels in the 

intake channel, a weir across the Sacramento River just downstream of the intake channel has 

been proposed. If this weir is constructed and is in place during periods of green sturgeon 

migration, it will likely impede upstream movement of adults and may increase downstream 

passage time for juveniles. If it concentrates predators as happens at RBDD when the gates are 

closed, it could also result in increased mortality of juvenile sturgeon. 

Water Diversions

 Aside from the proposed pumped storage reservoir(s) on the west side of the Sacramento 

Valley, no additional diversions from the Sacramento River above Sacramento are proposed in 

the near future. However, numerous diversions exist there already and most small diversions are 

unscreened. Many of the large diversions are now screened and the present emphasis is on 

screening smaller diversions. The intent of all this screening is to protect juvenile salmonids. 

Although loss of larval and juvenile sturgeon in these agricultural diversions has not been 
32 

documented, it is likely that losses occur, especially as most diversion intakes are near the bottom 

and sturgeon larvae are demersal. Present screen technology is probably not as effective for 

sturgeon as for salmonids. Information on white sturgeon behavior in relation to fish screens is 

available from studies done at UCD and at experimental facilities at Hood in the late 1970s and 

early 1980s. 

Water Temperature

 Impacts of possible changes in water temperature as the result of increased water storage in 

the Sacramento River basin are discussed earlier. 

 Water temperature that may be inadequate for spawning and egg incubation occurs in the 

Feather River in many years as the result of release of warmed water from Thermalito Afterbay. 

This may be one reason neither green nor white sturgeon are found in the river in low-flow years. 

It is not expected that water temperatures will become more unfavorable in the near future. 

Water Exports from the Delta

 We have already described the fact that varying numbers of green sturgeon are salvaged at 

the state and federal fish facilities in the south delta and that subadult green sturgeon have been 

found in seining surveys in Clifton Court Forebay. As export rates and through-delta movement 

of water increases in the future, the number of green sturgeon salvaged may increase. However, 

for white sturgeon, although year-class strength is related to freshwater flows in late winter and 

spring, it is not related to the volume of water exported from the delta. 

 A proposal to construct another diversion point on the Sacramento River near Hood to 

transport water into Snodgrass Slough and ultimately to the pumping plants has the potential for 

greater negative impact on green sturgeon than just increases in exports without physical changes 

in the delta’s “plumbing.” This screened diversion might entrain additional juvenile green 

sturgeon (beyond the number that now enter the Delta Cross Channel and Georgiana Slough) if it 

is not efficient for sturgeon. 

 A more significant impact of this additional screened diversion point is the potential for 

attracting upstream migrant adults to the downstream side of the screen through Snodgrass Slough 
33 

and the need to provide passage for them through or over the screen. The technology for doing 

this may not exist. 

Bay Filling

 Filling of San Francisco Bay has historically reduced foraging areas for sturgeon, but this 

activity has been curtailed in recent years. However, plans to add runway capacity to San 

Francisco International Airport will result in filling several square kilometers of the bay. This is a 

contentious issue and may not occur, but if it does, additional sturgeon foraging habitat will be 

lost without assurance that mitigation will be adequate. 

Exotic Species Introductions

 Introduction of exotic species is an ongoing problem in the estuary. The most likely impact 

on green sturgeon of these introductions is through changes in trophic interactions. Many of the 

recent introductions of invertebrates have greatly affected the benthic fauna in the delta and bays. 

The overbite clam, first observed in the estuary in 1988, is now the most common food of white 

sturgeon and was found in the only green sturgeon so far examined among nine fish collected in 

fall 2001. It appears to have replaced other clams in the diet of white sturgeon. 

 The recent introduction of the Chinese mitten crab (Eriocheir sinensis) may have added a 

new prey item for green sturgeon, or, perhaps, another competitor. So far, these have not been 

observed in the diet of either species of sturgeon. However, mitten crabs have had a major impact 

on the sturgeon fishery, as they are voracious bait stealers from late summer through winter in 

brackish areas. This has necessitated changes in fishing locations, techniques, and bait - all of 

which may have made sturgeon anglers less efficient. 

 In 1963-1964, native mysid shrimp (Neomysis mercedis) and amphipods (Corophium spp.) 

were the primary food of green sturgeon in the estuary (Ganssle 1966, Radtke 1966). This mysid 

is now much less abundant than in the 1960 and has been largely replaced in part of its range by 

the introduced Acanthomysis bowmani. Another isopod, Gammarus sp. was added to the delta’s 

benthic fauna recently and a native planktonic copepod (Eurytemora affinis) has given way to 

several introduced species, including Sinocalanus doerri and Pseudodiaptomous forbesi. 
34 

Toxicants

 Even with recent improvements in water quality in the Sacramento-San Joaquin system, the 

influence of toxicants, especially their chronic effects on survival and reproduction of aquatic 

biota, continue to be of concern. No specific information is available on contaminant loads or 

impacts in green sturgeon. However, white sturgeon in the past have contained high PCB loads 

(Kohlhorst 1980), although more recent data showing much lower contamination suggest these 

earlier results may have been erroneous (D. Kohlhorst, CDFG, pers. comm.; unpublished CDFG 

data). White sturgeon in the estuary do accumulate selenium, but tissue concentrations have 

varied among years without trend and do not seem to be related to fish size (White et al. 1989). 

The difference in distribution of green and white sturgeon (ocean migrants vs. estuarine 

inhabitants) probably makes green sturgeon less vulnerable than white sturgeon to 

bioaccumulation of contaminants found in the estuary. 

Klamath River System 

 Two important habitat characteristics critical to successful green sturgeon spawning and 

rearing in the Klamath River system are maintenance of suitable spawning habitats and 

maintenance of suitable water temperature, at least during egg incubation and larva rearing. 

 Deng (2000) suggested that green sturgeon eggs, because of there relative lack of 

adhesiveness, depend on being trapped in crevices in bedrock or under gravel. Larvae younger 

than 6 days posthatch show very limited mobility and older larvae exhibit strong negative 

phototaxis, behavior which would allow them to develop within relatively short, high gradient 

streams (ibid). Thus, the introduction of finer substrate material, especially covering bedrock, 

cobble, or coarse gravel, is probably detrimental to green sturgeon. 

 Cool water temperatures are also probably important to green sturgeon egg and larva 

development. Optimal temperatures for egg survival and development of other species of 

sturgeon is about 14 to 17o

C and egg and larva survival decreasing rapidly at higher temperatures 

(Wang et al. 1985). 
35 

 Past logging practices have contributed to sedimentation in the Klamath River system. The 

loss of sturgeon spawning habitat in the South Fork Trinity River is largely the result of road 

building and clear-cutting. Logging practices are much better than in the past, but any additional 

sedimentation in remaining spawning habitat in the Klamath system is likely to be detrimental to 

green sturgeon spawning success. 

 Both the Klamath and Trinity Rivers have upstream demands on water that could effect 

temperatures in the lower reaches where green sturgeon spawn and rear and the temperature effect 

of present and future water development on these rivers needs to be considered. 

 Eel River 

 The Eel River has probably been more affected by erosion from past logging and other land 

use practices than the Klamath-Trinity system. Also, water temperatures may be more of a 

problem in this drainage because of the more southern geographical location and lower elevation 

of the Eel River watershed. 

Other Coastal Rivers and Bays 

 Due to improvements in treatment of industrial and municipal waste and restriction on 

dumping such waste into bays, conditions for ocean migrant juveniles and adults have probably 

improved in most coastal bays in recent years. However, logging, road building, and agricultural 

activities, among others, in watersheds that historically contained green sturgeon may inhibit 

recolonization of these areas. 

Conservation Actions

Sacramento-San Joaquin System 

Angling Regulations 
36 

 Both species of sturgeon are now protected by sport angling regulations (no commercial 

harvest is permitted) that allow the year-round take of one fish per day between 117 and 183 cm 

TL. In addition, a closure of central San Francisco Bay during the herring spawning season 

(January 1-March 15) protects sturgeon when they are concentrated feeding on herring eggs. As 

female green sturgeon may not mature until they are about 150 cm, they are vulnerable to the 

sport fishery for many years. Their vulnerability is decreased by the fact that they spend most of 

this period in the ocean where they are infrequently caught. 

 No changes in angling regulations are contemplated at this time. Because legal-sized green 

sturgeon are easily distinguished from white sturgeon and are a very minor component of the 

sport fishery, closure of the estuary and its tributaries to green sturgeon fishing would be effective 

and cause little impact to the fishery. 

Enforcement Activities

 Active enforcement of sturgeon angling regulations is a priority at times and in areas where 

sturgeon are concentrated and vulnerable to the fishery, such as the delta to San Pablo Bay area in 

late winter and the upper Sacramento River during the spawning migration. The trophy status of 

white sturgeon and the consequent incentive for retaining oversize (>183 cm) fish is another 

impetus for active enforcement of sturgeon angling regulations. 

 No increase in CDFG enforcement activity for sturgeon is anticipated at this time. 

Current and Planned Operation of Red Bluff Diversion Dam

 See the above section on Habitat Impacts. 

Anadromous Fish Restoration Plan (AFRP)

 This component of the Central Valley Project Improvement Act (CVPIA) implements the 

CVPIA goal to double natural production of anadromous fishes (including sturgeon) in the 

Central Valley by this year (2002). Tools available include enhancing stream flows, relocating 

and screening diversions, and using up to 800,000 acre-feet of Central Valley Project yield for 

fish and wildlife restoration. We are not aware of any AFRP actions specifically designed to 
37 

benefit green sturgeon, but they may benefit from actions taken to increase production of other 

species. 

CALFED Bay-Delta Program

 The CALFED Program seeks to recover the green sturgeon by restoring its population 

distribution and abundance to historical levels. The CALFED Ecosystem Restoration Program 

Plan (ERPP) addresses some of the major factors limiting the green sturgeon population, 

including adequate stream flows for attracting adults to spawning areas in rivers, transporting 

young to nursery areas, illegal and legal harvest, and entrainment into water diversions. The 

ERPP calls for actions that restore ecological processes, restore spawning habitat, improve the 

aquatic food web, reduce stressors, and improve water quality. For instance, the ERPP could 

benefit green sturgeon by providing inflow to the delta for the Sacramento River greater than 

25,000 cfs during the March to May spawning period in at least 2 of every 5 years (an action 

based on production-flow relations for white sturgeon) and improving spring flows in major 

tributaries to the Sacramento River. Other beneficial actions include restoring natural meander 

belts; adding gravel substrate in upstream spawning areas; and restoring tidal perennial aquatic 

habitat, fresh emergent wetland, and delta sloughs. The ERPP also calls for eliminating migration 

barriers such as diversion dams, reducing stranding in the Yolo Bypass, and improving water 

quality to reduce concentrations of toxic substances in prey that can concentrate in sturgeon and 

adversely effect green sturgeon health and reproduction. A new state-of-the-art fish screen and 

fish salvage facility for the State Water Project will also help reduce export impacts on green 

sturgeon. Finally, the ERPP calls for research to fill in knowledge gaps for green sturgeon with 

respect to habitat requirements, distribution of spawning habitat, flow requirements, and factors 

limiting abundance. 

Klamath River System 

Angling Regulations

 From 1954 to 1977, the Klamath River was regulated by statewide sturgeon regulations 

which allowed the year-round take of one sturgeon per day with a minimum size of 102 cm TL; 
38 

snagging was prohibited. From 1978 to 1993, a further restriction on harvest was imposed in the 

form of a spawning closure that prohibited the take of sturgeon in the Klamath River from the 

mouth of the Trinity River upstream to and including Ishi Pishi Falls from April 1 through July 

15. In 1990, a maximum size limit of 183 cm was instituted and the minimum size limit was 

increased in 5-cm annual increments until it reached 117 cm. Since 1993, all sturgeon fishing has 

been prohibited in Del Norte, Humboldt, Siskiyou and Trinity counties. This closure covers all 

waters used by sturgeon in the Klamath-Trinity system. 

Enforcement Activities

 Local CDFG wardens monitor fisheries within their districts on the Klamath and Trinity 

rivers, and special enforcement activities have taken place where problems occur. 

Eel River 

Angling Regulations

 Sturgeon on portions of the Eel River where adult sturgeon have recently been observed by 

CDFG biologists and at all locations where juvenile sturgeon have been documented (Puckett 

1976) have been protected since 1993 by the same sturgeon fishery closure in effect for the 

Klamath River. This closure covers the Eel River from the mouth to rkm 153 and includes all 

waters in the South Fork Eel River downstream of Benbow Dam. 

Enforcement Activities

 CDFG enforcement personnel feel that enforcement problems on the Eel River are less than 

in the past because of reduced population in remote areas because of a decline in logging within 

the watershed (S. Downie, CDFG, pers. comm.). 

Other Coastal Rivers and Bays 

 Sturgeon fishing in rivers and bays in Del Norte and Humboldt counties has been prohibited 
39 

since 1993. These closed waters include the Smith River, Humboldt and Arcata bays, and all tidal 

sections of rivers, creeks, and bays. From Mendocino County south, green sturgeon fisheries are 

subject to the general sturgeon angling regulations: a year-round season with one fish per day 

between 117 and 183 cm TL. 

 

CONCLUSIONS 

 In this section we present our conclusions about the status of green sturgeon in California, 

based on available information, and generally organized according to some concerns expressed in 

the listing petition. 

Green sturgeon have suffered a general (or recent) decline in abundance - Measures available to 

the CDFG for assessing green sturgeon abundance, or abundance trends, are all deficient in some 

way: they are indirect (population estimates from tagging), rely on small numbers of fish (San 

Francisco Bay Outflow Study catches), are of short duration (RBDD catches and CDFG seine 

catches in the Klamath River estuary, rely on unreliable species identification (state and federal 

fish facility salvage), or lack data to correct for temporal changes in effort (tribal harvest in the 

Klamath River system). Only two measures exhibit a significant decreasing trend over their 

period of record and these are probably the least reliable abundance indicators (salvage records 

and tribal harvest). Other abundance measures exhibit no time trend. 

 In this regard, the statement that the green sturgeon has suffered an “88% decline in most of 

[its] range” (Musick et al. 2000:10) cited by the listing petition, and the December 14, 2001 

Federal Register notice of petition finding, cannot be substantiated with any data. Musick et al. in 

turn cite Houston (1988) who actually states that “there is no evidence for a general population 

decline” (p. 288). An inquiry from R. Schaffter of the CDFG to Dr. Musick resulted in an E-mail 

response to Mr. Schaffter from Dan Ha on February 13, 2002, who indicated that he had written 

the sections on sturgeon in Musick et al. (2000) and that his response had been “read and 

approved” by Dr. Musick. His response is as follows: 

 “We would like to apologize for the missing citations, and incorrect figure in the 
40 

section on green sturgeon (which is also incorrect in the section on white). It should read, 

‘...98% decline in most of its range (Cech 1992, Hart 1973),... 

 The misunderstanding comes from the need for compressing a great deal of 

information into a short paper. The original draft of this section read as follows, ‘The 

abundance of all west coast sturgeons, including green, suffered approximately an 88% 

decline in California, as inferred from commercial catch rates (Cech 1992). Similar declines 

occurred in other areas (Hart 1973). Early commercial fisheries records do not distinguish 

between white and green sturgeons, and hence, exact figures for each are unavailable.’ 

NMFS did not distinguish between white and green sturgeons in its records until 1980. 

 We do not debate that this is a tenuous estimation, however, it is the best 

approximation we have. Note that this is not the only risk criterion we found applicable to 

green sturgeon; it also has the risk factors of rarity and specialized habitat requirements. 

Furthermore, we acknowledge in the article that data are needed for precise determination of 

status.” 

 Hart (1973) presents no information concerning green sturgeon abundance trends, although 

he does show commercial harvest figure for white sturgeon in the Fraser River. Cech (1992) 

presents sturgeon party boat catch figures during a period of declining party boat fishing effort in 

his article on white sturgeon. 

Green sturgeon distribution has been restricted - Restrictions in green sturgeon distribution 

mostly would occur as the result of loss of spawning habitat, either through dam building, 

sedimentation, or degradation of water quality (including temperature changes). There is no 

evidence that their marine habitat has been diminished, although historically, potential foraging 

area in San Francisco Bay has been reduced by bay fill. 

 Historical accounts, and what little data are available, support the loss of spawning habitat in 

the South Fork Trinity River and the Eel River system due to anthropomorphic changes and 

natural events that, in combination, increased sedimentation. However, observations in the 1990s 

suggest that a small spawning population of green sturgeon still uses the Eel River. 

 Loss of habitat in the Klamath River and in Central Valley streams is more problematic. 
41 

Both the Klamath and Trinity Rivers have barriers to upstream migration of sturgeon that are well 

below existing reservoirs, so the dams that created those reservoirs are unlikely to have blocked 

access to historical spawning areas. 

 In the Central Valley, the most likely loss of spawning habitat is in the Feather River, as 

Oroville Dam blocks access to potential spawning habitat and Thermalito Afterbay warm water 

releases may increase temperatures to levels that are undesirable for spawning and incubation. 

Nevertheless, anecdotal evidence suggests that adult green sturgeon are still found in the Feather 

River in high flow years, presumably as they take advantage of intermittent opportunities for 

successful spawning. 

 We know of no evidence that green sturgeon historically spawned in the San Joaquin River. 

Based on movement of other fishes in the delta, young green sturgeon found in the lower San 

Joaquin River could easily, and most likely, have come from the known spawning population in 

the Sacramento River. No sturgeon of either species appear to have trapped behind Friant Dam 

on the San Joaquin River when it was constructed in the 1940s (R. Kelly, CDFG, pers. comm.) 

 Present spawning of green sturgeon in the remaining accessible areas of the Sacramento 

River upstream of Hamilton City, and their apparent ready use of additional spawning habitat 

made available by the re-operation of RBDD in the early 1990s, suggest that they historically 

spawned above Shasta Dam. It is, therefore, surprising that only white sturgeon were ever 

observed in Lake Shasta (Fisk 1963). 

Exploitation presently threatens green sturgeon - The two areas of greatest green sturgeon harvest 

are the Klamath River and estuaries and bays in Oregon and Washington. While numerical 

harvest estimates by the tribal fisheries in the Klamath River are available, we have no 

information concerning effort, so trends in catch per effort cannot adequately be explored. As the 

important statistic is harvest rate (fraction of the population harvested annually), not number of 

fish caught, either estimates of abundance or a tagging program are needed to adequately evaluate 

exploitation of the Klamath River stock. 

 Limited information of that sort is available for green sturgeon in the Sacramento-San 

Joaquin system. Annual harvest rate estimates from the tagging program there ranged from 2.8 to 
42 

7.7% and almost all of that harvest was in Oregon and Washington. Because few green sturgeon 

are tagged in most years, tag recaptures by fishers are rare. Combining all tag returns and all 

releases yields an “average” harvest rate of 2.2%. The impact of these low harvest rates on the 

population is unknown. While it is generally felt that harvest rates >10% will lead to long-term 

population declines in white sturgeon (Kohlhorst et al. 1991), even lower rates may be excessive 

for a rarer species like green sturgeon. 

Adequacy of present conservation measures - In California, state regulations allow only sport 

fishing for green sturgeon. Besides restrictive size and creel limits, sturgeon angling is prohibited 

in all areas of the Klamath River system inhabited by green sturgeon and in most of the Eel River. 

The only legal harvest in these north coast rivers is by the tribal fisheries in the Klamath system. 

The extent of illegal harvest is unknown. 

 In the Sacramento-San Joaquin system, although some green sturgeon are harvested, angling 

regulations are almost irrelevant because almost all harvest of fish tagged there takes place in 

other states. Harvest rates for these fish were estimated in years before the present 117-183-cm 

slot limit was instituted, so within the estuary and its tributaries, green sturgeon are afforded even 

more protection than reflected in those estimates. The increase in the minimum size limit from 

102 to 117 cm is probably more beneficial than the maximum 183-cm limit, as it protects many 

subadult green sturgeon that sometimes enter the estuary. 
43 

LITERATURE CITED

Cech, J.J. 1992. White sturgeon. Pages 70-71 in: W.S. Leet, C.M. Dewees, and C.W. Haugen, 

editors. California’s living marine resources and their utilization. California Sea Grant, 

Davis, California. 

Deng, X. 2000. Artificial reproduction and early life stages of the green sturgeon (Acipenser 

medirostris). MS Thesis, University of California, Davis, California. 

Fisk, L.O. 1963. The Shasta Lake sturgeon fishery. California Department of Fish and Game, 

Inland Fisheries Administrative Report 63-12. 

Gaines, P.D. and C.D. Martin. 2001 (draft). Abundance and seasonal, spatial and diel distribution 

patterns of juvenile salmonid passing the Red Bluff Diversion Dam, Sacramento River. Red 

Bluff Research Pumping Plant Report Series, Volume 14. U.S. Fish and Wildlife Service, 

Red Bluff, California. 

Ganssle, D. 1966. Fishes and decapods of San Pablo and Suisun bays. Pages 64-94 in: D.W. 

Kelley, compiler. Ecological studies of the Sacramento-San Joaquin Estuary, part I. 

California Department of Fish and Game, Fish Bulletin 133. 

Hart, J.L. 1973. Pacific fishes of Canada. Fisheries Research Board of Canada, Bulletin 180:82-

84. 

Healey, T.P. 1973. Studies of steelhead and salmon emigration in the Trinity River. 

Anadromous Fisheries Branch Administrative Report 73-1. California Department of Fish 

and Game, Sacramento, California. 

Hopelain, J.S. 1988. A four-year summary of seining/tagging operations in the lower Klamath 

River with emphasis on mature fall chinook salmon, coho salmon, and steelhead trout 1984 

through 1987. Draft report, California Department of Fish and Game, Sacramento 

California. 

Houston, J.J. 1988. Status of the green sturgeon, Acipenser medirostris, in Canada. Canadian 

Field-Naturalist 102:286-290. 

Kohlhorst, D.W. 1976. Sturgeon spawning in the Sacramento River in 1973, as determined by 

the distribution of larvae. California Fish and Game 62:32-40 

47 

Kohlhorst, D.W. 1980. Recent trends in the white sturgeon population in California’s 

Sacramento-San Joaquin Estuary. California Fish and Game 66:210-219. 

Kohlhorst, D.W., L.W. Botsford, J.S. Brennan, and G.M. Cailliet. 1991. Aspects of the 

structure and dynamics of an exploited central California population of white sturgeon 

(Acipenser transmontanus). Pages 277-293 in: P. Willot, editor. Acipenser: Actes du 

premier colloque international sur l’esturgeon. CEMAGREF, Bordeaux, France. 

Moyle, P.B, P.J. Foley and R.M. Yoshiyama. 1992. Status of green sturgeon, Acipenser 

medirostris, in California. Final report submitted to National Marine Fisheries Service, 

Terminal Island, California, May 1992. 

Moyle, P.B. and R.M. Yoshiyama, 1992. Fishes, aquatic diversity management areas, and 

endangered species-A plan to protect California’s Native Aquatic Biota. The California 

Policy Seminar, University of California 1992, pp 69-80. 

Musick, J.A. and 17 others. 2000. Marine, estuarine, and diadromous fish stocks at risk of 

extinction in North America (exclusive of Pacific salmonids). Fisheries 25(11):6-30. 

Nakamoto, R.J. and T.T. Kisanuki. 1995. Age and growth of Klamath River Green Sturgeon 

(Acipenser medirostris). U. S. Fish and Wildlife Service, Klamath River Fishery Resource 

Office, Arcata, California. 

Puckett, L.K. 1976. Observations on the downstream migrations of anadromous fishes within 

the Eel River system. California Department of Fish and Game Memorandum Report, 

January 1976. Sacramento, CA. 

Radtke, L.D. 1966. Distribution of smelt, juvenile sturgeon, and starry flounder in the 

Sacramento-San Joaquin Delta with observations on food of sturgeon. Pages 115-129 in: 

J.L. Turner and D.W. Kelley, compilers. Ecological studies of the Sacramento-San Joaquin 

Estuary, part II. California Department of Fish and Game, Fish Bulletin 136. 

Ricker, W.E. 1975. Computation and interpretation of biological statistics of fish populations. 

Fisheries Research Board of Canada Bulletin 191. Ottawa, Quebec, Canada. 

Schaffter, R.G. 1997. White sturgeon spawning migrations and location of spawning habitat in 

the Sacramento River, California. California Fish and Game 83:1-20. 

USFWS (U. S. Fish and Wildlife Service). 1981. Klamath River Fisheries Investigation 
48 

Program. Annual Report 1980. Arcata, California. 

USFWS. 1982. Klamath River fisheries investigation program, Annual Report - 1981. Arcata 

California. 

USFWS. 1983. Klamath River fisheries investigation program, Annual Report - 1982. Arcata 

California. 

USFWS. 1984. Klamath River fisheries investigation program, Annual Report - 1983. Arcata 

California. 

USFWS. 1985. Klamath River fisheries investigation program, Annual Report - 1984. Arcata 

California. 

USFWS. 1988. Klamath River Fisheries Assessment Program, Annual Report 1987. Arcata, 

California. 

USFWS. 1989. Klamath River Fisheries Assessment Program, Annual Report 1988. Arcata, 

California. 

USFWS. 1992. Klamath River Fisheries Assessment Program, Annual Report 1990 and 1991. 

Arcata, California. 

USFWS. 1994. Klamath River Fisheries Assessment Program, Annual Report 1992. Arcata, 

California. 

USFWS. 1998. Klamath River Fisheries Assessment Program, Annual Report 1995. Arcata, 

California. 

USFWS. 1999. Klamath River Fisheries Assessment Program, Annual Report 1996. Arcata, 

California. 

Wang, Y.L., F.P. Binkowski, and S.I. Doroshov. 1985. Effect of temperature on early 

development of white and lake sturgeon, Acipenser transmontanus and Acipenser 

fulvescens. Pages 43-50 in: F.P. Binkowski and S.I. Doroshov, editors. North American 

sturgeons. Dr. W. Junk Publishers, Dordrecht, Netherlands. 

White, J.R., P.S. Hofmann, K.A.F. Urquhart, D. Hammond, and S. Baumgartner. 1989. 

Selenium verification study, 1987-1988. A report to the California State Water Resources 

Control Board from the California Department of Fish and Game, April 1989. 
49 

Table 1. Green sturgeon tagging summary for the Sacramento-San Joaquin Estuary, 1948-2001. 

Year Number tagged

1948 36 

1949 6 

1954 26 

1967 25 

1968 28 

1974 7 

1979 26 

1984 24 

1985 19 

1987 6 

1990 12 

1991 5 

1993 2 

1997 8 

2001 45 

Grand 

Total 

275
50 

Table 2. Recovery information for green sturgeon tagged in the Sacramento-San Joaquin 

Estuary from 1948 to 1987. 

 Date Total Date Location Recapture Days at 

 tagged length (cm) recaptured recaptured method large

 22-Sep-48 65 7-Apr-49 Monterey Bay, CA Commercial 197 

 27-Sep-54 130 28-Aug-58 Columbia River, WA Commercial gill net 1431 

 29-Sep-54 104 4-Dec-55 Columbia River, OR Commercial otter trawl 431 

 30-Sep-54 117 1-Sep-57 Winchester Bay, OR Commercial gill net 1067 

 11-Oct-67 127 25-Jul-69 Grays Harbor, WA Commercial 653 

 15-Oct-67a 114-127a 20-Sep-68 Columbia River, OR Commercial 341 

 15-Oct-67a 114-127a 17-Aug-70 Columbia River, OR Commercial 1037 

 15-Oct-67a 114-127a 1-Jan-71 San Pablo Bay, CA Sport 1174 

 27-Oct-67 117 23-Dec-67 Monterey Bay, CA Commercial halibut trawl 57 

 14-Sep-79 106 2-Sep-80 Westport, WA Tag found in gill net 354 

 11-Oct-79 145 14-Nov-79 Bodega Head, CA Unknown 34 

 19-Sep-84 116 11-Dec-84 San Pablo Bay, CA Sport (CPFV) 83 

 10-Sep-84 108 9-Jul-88 Grays Harbor, WA Commercial gill net 1398 

 11-Sep-84 108 8-Sep-87 Columbia River, OR Commercial gill net 1092 

 2-Oct-84 129 1-Aug-86 Columbia River, WA Commercial gill net 668 

 9-Sep-85 188 30-Jul-86 Columbia River, OR Commercial gill net 324 

 11-Sep-85 124 15-Sep-85 San Pablo Bay, CA? Unknown 4 

 23-Oct-87 106 10-Oct-90 Near Astoria, OR Commercial 1083 

 

a

 Exact date of tagging unknown; length also unknown, but within range shown. 
51 

Table 3. Monthly mean length (fork length in 1986-1993, total length in 1996-2001, 

measurement method unknown in 1994-1995), standard deviation, and range of larval and postlarval sturgeon captured at the Glenn-Colusa Irrigation District diversion in a fyke trap from 

1986 to 1990 and rotary-screw trap from 1991 to 2001. Only fish <100 mm are included; 

number caught and the range of lengths are the only data available for 1994 and 1995; no 

sampling was conducted in 1998. 

May June July

Year Mean S.D. Range N Mean S.D. Range N Mean S.D. Range N

1986 38.5 2.1 37-40 2

1987 

1988 30.0 7.1 19-38 6 37.1 10.7 26-38 9

1989 47.0 - 47 1

1990 24.7 0.6 24-25 9 27.8 3.6 23-33 3

1991 38.2 8.3 24-61 23 37.6 6.6 25-67 110

1992 34.5 4.3 30-51 36 30.4 5.9 26-80 110 31.4 2.4 27-35 163

1993 30.3 4.5 21-43 76 32.3 3.6 27-39 11 32.8 4.4 26-76 504

1994 26-58 12 26-36 26

1995 28-35 20 22-79 205

1996 34.0 6.9 23-51 41 41.8 22.0 26-98 9 36.1 8.7 20-70 152

1997 31.1 2.2 26-36 28 33.1 4.9 23-53 125 35.3 4.6 26-46 53

1998 - - - - - - - - - - - -

1999 35.9 4.2 30-44 23 36.6 8.1 25-85 170

2000 29.0 0.0 29 1 36.6 11.9 28-71 12 36.9 7.6 24-57 17

2001 39.0 6.1 31-46 3 42.2 16.6 27-87 12 37.1 5.5 24-46 16

August September October

Year Mean S.D. Range N Mean S.D. Range N Mean S.D. Range N

1986 50.0 0.0 50 2 

1987 

1988 

1989 

1990 

1991 37.6 4.3 29-41 6 

1992 31.8 3.3 28-37 11 

1993 35.5 5.7 29-62 89 40.0 - 40 1

1994 

1995 29-52 79 57-75 3

1996 34.9 8.5 26-92 112 

1997 37.0 4.7 29-46 20 37.5 0.7 37-38 2 35.0 0.8 34-36 4

1998 - - - - - - - - - - - -

1999 35.0 11.2 30-70 43 36.0 0.0 36-36 2 34.0 - 34 1

2000 35.0 4.2 32-38 2 32.0 - 32 1

2001 28.0 0.0 28 1
52 

Table 4. Month and location of juvenile green sturgeon catches by San Francisco Bay Outflow Study otter and midwater trawl sampling from 1980 to 2001. 

 Location 

Month South San Francisco Bay Central San Francisco Bay San Pablo Bay Suisun Bay Delta Total

1 1 1 

2 1 1 2 4 

3 1 2 3 

4 2 1 3 6 

5 1 2 3 6 

6 2 1 6 1 10 

7 1 2 3 6 

8 1 5 1 7 

9 1 2 1 3 7 

10 1 4 1 6 

11 4 4 

12 1 1 

Total 3 6 10 21 14 61

Table 5. Green sturgeon catches during juvenile sturgeon sampling designed to index year-class strength of white sturgeon in the Sacramento-San Joaquin Estuary, 1988-2001. 

 

Year Month Day Location Method Sampling duration (hrs) Total Length

1988 8 25 Honker Bay - Simmons Pt. Set gill net 24:00 52 

1988 9 14 Grizzly Bay - Dolphin Set gill net 24:50 54 

1988 9 20 Southhampton Bay Set gill net 21:25 55 

1988 9 21 San Pablo Bay - Petaluma Channel Set gill net 19:55 59 

1989 8 28 Suisun Bay - Lower Reserve Fleet Set gill net 25:45 53 

1989 8 29 San Pablo Bay - Rockwall Set gill net 22:00 50 

1989 8 29 Carquinez Strait - Ozol Set gill net 24:20 48 

1989 8 29 Carquinez Strait - Ozol Set gill net 24:20 54 

1989 10 23 Sacramento R. - Rio Vista Otter trawl 0:10 32 

1989 4 25 Chipps Is. Set gill net 20:45 37 

1989 4 25 Sacramento R. - Chain Is. Set gill net 21:40 34 

1989 5 25 San Pablo Bay - Rockwall Set gill net 21:30 71 

1989 7 24 Sherman Lake Set gill net 19:25 54 

1989 7 27 San Pablo Bay - Rockwall Set gill net 20:00 49 

1989 7 27 Suisun Bay - Lower Reserve Fleet Set gill net 19:00 66 

1990 7 2 Sacramento R. - Decker Is. Drift gill net 0:40 46 

1990 7 2 Sacramento R. - Decker Is. Drift gill net 0:40 47 

1998 8 19 San Pablo Bay - Rockwall Set-line 20:00 57 

2000 7 20 Suisun Bay - Garnet Pt. Set-line 20:00 57 

2000 7 24 Broad Sl Set-line 20:00 169 

2000 8 31 San Pablo Bay - Rockwall Set-line 20:00 122
53 

Table 6. Juvenile green sturgeon catches in the mainstem Eel River from 1967 to 1970, 

expressed as fish per sample day. NS = not sampled. 

Green sturgeon per day

Site Year May Jun Jul Aug Sep Oct-Nov

Rio Dell, rkm 32 1967 NS NS NS 0.1 NS 0 

Holmes, rkm 58 1967 NS NS NS 0.6 0 0 

McCann, rkm 76 1967 NS NS NS 4.4 NS NS 

McCann 1968 0 0 0.4 0 0 0 

McCann 1969 0 0 12.3 0 0 0 

McCann 1970 0 1.0 0a 0 0 0 

Eel Rock, rkm 88 1967 NS NS NS 3.7 0 NS 

Ft. Seward, rkm 109 1968 27.6 0 0 0 0 5 

a

 Only 1 sample day during July 1970 

 

Table 7. Age-length key from green sturgeon collected in the Sacramento-San Joaquin Estuary from 1965 to 1976. 

Length Age

group 1 2 3 4 5 6 7 8 9 Total

35-39 1.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 1.000 

40-44 0.000 1.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 1.000 

45-49 0.000 

50-54 0.000 1.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 1.000 

55-59 0.000 0.444 0.333 0.222 0.000 0.000 0.000 0.000 0.000 1.000 

60-64 0.000 0.176 0.471 0.353 0.000 0.000 0.000 0.000 0.000 1.000 

65-69 0.000 0.158 0.211 0.421 0.105 0.053 0.000 0.053 0.000 1.000 

70-74 0.000 0.000 0.118 0.353 0.353 0.118 0.059 0.000 0.000 1.000 

75-79 0.000 0.000 0.033 0.333 0.467 0.167 0.000 0.000 0.000 1.000 

80-84 0.000 0.000 0.053 0.105 0.421 0.263 0.105 0.053 0.000 1.000 

85-89 0.000 0.000 0.000 0.077 0.385 0.538 0.000 0.000 0.000 1.000 

90-94 0.000 0.000 0.000 0.000 0.000 0.400 0.400 0.200 0.000 1.000 

95-99 0.000 0.000 0.000 0.000 0.000 0.667 0.333 0.000 0.000 1.000 

100-104 0.000 0.000 0.000 0.200 0.600 0.000 0.000 0.000 0.200 1.000 

105-109 0.000 0.000 0.000 0.000 0.000 0.000 0.667 0.333 0.000 1.000 

110-114 0.000 0.000 0.000 0.000 0.250 0.000 0.500 0.000 0.250 1.000 

115-119 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 1.000
54 

Table 8. Size statistics for green sturgeon captured during tagging in the Sacramento-San 

Joaquin Estuary from 1948 to 2001. 

Year Total measured Mean total length (cm) Standard deviation (cm) Coefficient of variation

1948 36 89.2 16.98 19.0% 

1949 6 114.5 36.72 32.1% 

1954 25 106.3 13.88 13.1% 

1967 25 115.7 16.49 14.3% 

1968 28 124.2 25.48 20.5% 

1974 103 80.5 19.40 24.1% 

1979 26 126.9 21.29 16.8% 

1984 31 122.8 32.13 26.2% 

1985 66 101.8 28.31 27.8% 

1987 11 94.7 18.83 19.9% 

1990 20 118.7 32.29 27.2% 

1991 11 108.7 17.22 15.8% 

1993 5 108.8 30.64 28.2% 

1994 11 74.5 17.59 23.6% 

1997 14 122.2 26.68 21.8% 

1998 19 94.9 23.40 24.6% 

2001 208 109.9 22.42 20.4%

Table 9. Average total length, standard deviation, and range of Lower Klamath River green sturgeon harvested in tribal fisheries from 1980 through 1992 (Table 36, p 58, USFWS 1994). Data for 1980-1985 are from fish taken in gill nets, beach seine, and by hook and line. Data 

from 1986 to 1992 are for gill-netted sturgeon only. 

Mean Total Standard Sample Year Length (cm) Deviation Size Range (cm) 1980 173.0 15.25 90 148 - 211 

1981 176.3 17.62 157 138 - 232 

1982 170.7 18.78 82 130 - 216 

1983 170.9 13.64 45 145 - 208 

1984 175.0 16.29 65 140 - 214 

1985 174.8 17.44 34 130 - 208 

1986 169.2 20.99 21 134 - 210 

1987 176.9 23.71 21 143 - 260 

1988 178.8 23.20 16 139 - 218 

1989 169.5 20.05 20 136 - 196 

1990 178.4 20.71 51 129 - 217 

1991 179.9 19.76 63 130 - 222 

1992 178.3 23.94 35 134 - 238 
55 

Table 10. Sturgeon catch during tagging, ratios of green to white sturgeon in the catch, and abundance estimates, 1954-2001. 

Legal-sized Legal-sized 

white green 

 Legal (>=102 cm) Sublegal (<102 cm) sturgeon sturgeon 

Year White Green W/G G/W White Green W/G G/W abundance abundance

1954 961 17 56.5 0.018 33 8 4.1 0.242 11,200 198 

1967 1,612 26 62.0 0.016 114,700 1,850 

1968 1,080 28 38.6 0.026 40,000 1,037 

1974 713 7 101.9 0.010 62 103 0.6 1.661 20,700 203 

1979 1,368 26 52.6 0.019 62 9 6.9 0.145 100,300 1,906 

1984 2,551 24 106.3 0.009 148 7 21.1 0.047 117,600 1,106 

1985 2,419 19 127.3 0.008 68 47 1.4 0.691 107,800 847 

1987 982 6 163.7 0.006 42 5 8.4 0.119 97,800 598 

1990 596 12 49.7 0.020 353 8 44.1 0.023 75,600 1,522 

1991 403 5 80.6 0.012 529 6 88.2 0.011 72,700 902 

1993 207 2 103.5 0.010 271 3 90.3 0.011 46,700 451 

1994 274 0 0.000 552 11 50.2 0.020 

1997 1,015 8 126.9 0.008 354 6 59.0 0.017 141,900 1,118 

1998 1,263 3 421.0 0.002 275 16 17.2 0.058 144,400 343 

2001a 771 23 33.5 0.030 173 62 2.8 0.358 120,000 3,580 

Total 16,215 206 78.7 0.013 2,922 291 10.0 0.100 

 

a

 Excluding August catches 
56 

Table 11. Estimated harvest of green sturgeon in the Klamath River. Data provided by J. Devore, Washington Department of Fish and Wildlife and S. King, Oregon Department of Fish and Wildlife. (from Appendix 2 of the listing petition) 

 Year Yurok2 Hoopa3 Karuk4 Poaching5 Total

 1980 700+ - unknown 400+ 1100+ 

 1981 880+ - unknown 70+ 950+ 

 1982 397+ - unknown 50+ 447+ 

 1983 406+ - unknown unknown 406+ 

 1984 394+ - unknown unknown 394+ 

 1985 351+ 10 unknown unknown 361+ 

 1986 421+ 30 unknown unknown 451+ 

 1987 171+ 20 unknown unknown 191+ 

 1988 212+ 20 unknown unknown 232+ 

 1989 268+ 30 unknown unknown 298+ 

1980s average 420+ 22 unknown unknown 483+ 

 1990 242+ 20 unknown unknown 262+ 

 1991 312+ 13 unknown unknown 325+ 

 1992 212+ 3 unknown unknown 215+ 

 1993 417+ 10 unknown unknown 427+ 

 1994 293+ 14 unknown unknown 307+ 

 1995 131+ 2 unknown unknown 133+ 

 1996 119+ 17 unknown unknown 136+ 

 1997 306+ 7 unknown unknown 313+ 

 1998 335+ 10 unknown unknown 345+ 

 1999 184+ 27 unknown unknown 211+ 

1900s average 255+ 12 unknown unknown 267+ 

 

a

 Available harvests estimates are biased low by variable and inconsistent sampling efforts based on voluntered data. b

 Some Yurok harvest occurs prior to annual monitoring activities of the USFWS. c USFWS data onlv available from 1985. Available harvest estimates are biased low by variable and inconsistent sampling effort based on volunteered data. d Karuk harvest is not monitored by the USFWS. e

 Illegal snag harvest occurred at Coon Creek Falls after 1977, where a debris slide created a migration obstacle. 
57 
56 

Table 12. Annual estimates of harvest rate and catch for green sturgeon tagged in the Sacramento-San Joaquin Estuary. 

Year Tagged 1st -year returns Harvest rate Abundance Catch

1948 36 1 0.028 

1949 6 0 0 

1954 27 0 0 

1967 25 0 0 

1968 28 0 0 

1974 7 0 0 

1979 26 2 0.077 1,906 147 

1984 24 1 0.042 1,106 46 

1985 19 1 0.053 847 45 

1987 6 0 0 

1990 12 0 0 

1991 5 0 0 

1993 2 0 0 

1994 0 0 0 

1997 8 0 0 

1998 0 0 0 

2001 45 Incomplete 

Overall 0.022a

 a

 Excluding 2001, for which 1st year returns are not complete. 
57 

Figure 1. Monthly catch per acre-foot and median total length of sturgeon sampled in rotaryscrew traps at Red Bluff Diversion Dam, 1995-2000 (Figure 1 in Gaines and Martin 2001). 
58 

0

100

200

300

400

500

600

700

800

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Year

Num

ber of Sturgeon

Figure 2. Annual catch of sturgeon <100 mm FL at the Glenn-Colusa Irrigation District bypass 

rotary-screw trap from 1991 to 2001. The trap was not fished in 1998. 
59 

1984 1985 1986 1987 1988 1989 1990

Year

0

0.1

0.2

0.3

0.4

0.5

Sturg

e

o

n

C

atc

h

p

er S

e

ni e

H

a

ul Figure 3. Annual catch per seine haul of green sturgeon in the Klamath River estuary, 1984-

1990. 
60 

Figure 4. 

Total length frequencies of green sturgeon captured during tagging in the Sacramento-San 

Joaquin Estuary in 1974, 1985, and 2001. 

0

10

20

30

40

0

10

20

30

40

N

u

m

b

er

53 63 73 83 93 103 113 123 133 143 153 163 173 183 193

0

10

20

30

40

1974

1985

2001

Total length (cm)
61 

Figure 5. Estimated age 

frequency of green sturgeon < age 9 captured during tagging in the Sacramento-San Joaquin 

Estuary in 1974, 1985, and 2001. Letters above bars indicate year types, where C = critically 

dry, D = dry, BN = below normal, AN = above normal, and W = wet. 

0

10

20

30

40

50

60

1973 1972 1971 1970 1969 1968 1967 1966 1965

 Year Class

0

10

20

30

40

50

60

Number

1984 1983 1982 1981 1980 1979 1978 1977 1976

 Year Class

123456789

0

10

20

30

40

50

60

Age

2000 1999 1998 1997 1996 1995 1994 1993 1992

 Year Class

1974

1985

2001

W

W W

BN W BN

BN

WW

W W

W

W

W

W

BN

AN AN

D 

D 

C 

C 

C 
62 

DRAFT

Figure 6. Mean fork length of sturgeon captured weekly by rotary-screw traps at the Red Bluff 

Diversion Dam from 1995 to 1998. Figure 1 in February 9, 1999 memorandum from P. Gaines, 

USFWS to P. Ward, CDFG. (For original data, contact Phillip Gaines, USFWS, Red Bluff, 

California.) 
63 

012345012345670

10

20

30

400

20

40

60

80

100

120

1400

50

100

150

200

250

300

3500

20

40

60

80

100

1200

20

40

60

80

100

1200

10

20

30

40

50

60

70

8002468

10

12

14

1988

1990

1991

1992

1993

1996

1997

1998

2000

2001

Midpoint of length group (cm)

Number of sturgeon

18 23 28 33 38 43 48 53 58 63 68 73 78 83 88 93 98

02468

10
64 

Figure 7. Length frequency distribution of sturgeon <100 mm caught by the Glenn-Colusa 

Irrigation District rotary-screw trap from 1988 to 2001. Data from 3 years are not included: only 

one 47-mm fish was caught in 1989 and individual lengths are not available for 1994 and 1995. 

Length measurements are total length in 1988-1993 and fork length in 1996-2001. Note that 

scale on the ordinate varies between years as catches differed annually. 
65 

May June July August September October

30

35

40

45

Month

M

e

a

n

L

e

n

g

ht

1991 1992 1993 1996 1997 1999 2000 2001
66 

Figure 8. Monthly mean lengths of sturgeon <100 mm caught by the Glenn-Colusa Irrigation 

District rotary-screw trap from 1991 to 2001. Years with <3 months data and months with only 

1 fish measured are excluded. Length measurements are total length in 1988-1993 and fork 

length in 1996-2001. Data are in Appendix C. 
67 

15 25 35 45 55 65 75 85 95 105 115

0

2

4

6

8

10

12

14

16

Midpoint of length group (cm TL)

N

u

m

b

er

Figure 9. Length frequency of green sturgeon caught in otter and midwater trawls by the San 

Francisco Bay Outflow Study from 1980 to 2001. 
68 

Figure 10. Length frequency distribution of green sturgeon caught in the Sacramento-San 

Joaquin Delta with gill nets and otter trawl from September 1963 to August 1964 (After Radtke 

1966, Figure 7). 

21 24 27 30 33 36 39 42 45 48 51 54 57

0

10

20

30

40

50

Fork length (cm)

N

u

m

b

er

Gill net Otter trawl
69 

0

5

10

15

20

3 8 13 18 23 28 33 38 43 48 53 58 63 68 73 78

0

5

10

15

N

20

u

m

b

er

State Fish Facilities

Federal Fish Facilities

Midpoint of length group (cm FL)
70 

Figure 11. Length frequency distribution of green sturgeon collected at the state and federal fish 

facilities in the South Sacramento-San Joaquin Delta from 1968 to 2001. 
71 

Figure 12. Length-age relation for Klamath River green sturgeon collected during 1979-1982, 

including a von Bertalanffy growth equation for ages 1-30 (Figure 51, page 138, USFWS 1993). 
72 

Figure 13. Length-age relation for green sturgeon from the Klamath River, 1990-1993 (Figure 4, 

page 10, Nakamoto and Kisanuki 1995). 
73 

Figure 14. Combined length frequency distribution of Klamath River adult male and female 

green sturgeon captured during 1980-1983 by beach seine, gill net and hook and line (Figure 53, 

page 128, USFWS 1984). 
74 

70 80 90 100 110 120 130 140 150 160 170 180 190 200 210

0

2

4

6

8

10

Length (cm)

Num

b

er of s ut rg

e

o

n

Figure 15. Length frequency of green sturgeon seined in the Klamath River estuary, May 17 to 

August 1, 1977. Method of measurement (fork or total length) was not recorded. 
75 
76 

Figure 16. Length frequency distributions of green sturgeon captured by beach seine and gill net 

in the Klamath River estuary, 1979-1984 (Figure 47, page 136, USFWS 1985). 
77 

0

10

20

30

0

10

20

30

0

10

20

30

0

10

20

30

1984

n=16

1985

n=21

1986

n=74

1987

n=159

Fork Length - cm

Num

b

er of Sturg

e

on 0

10

20

30

Figure 17. Length frequency of juvenile green sturgeon captured in California Department of 

Fish and Game beach seining in the Klamath River estuary, 1984-1990. 

10 16 22 28 34 40 46 52 58 64 70 76 82 88 94 100

0

10

20

30

1988

n=50

1989

n=19

1990

n=61

0

10

20

30
78 

0

5

10

15

Number of Sturgeon

July

Aug

Sep

51 76 102 127 152 178 203 229 254

Total Length -- mm

Figure 18. Length by month of YOY green sturgeon captured by fyke net in the Trinity River 

near Willow Creek in 1968 (Healey 1973). 
79 

Figure 19. Daily lengths of green sturgeon captured in rotary-screw traps at Big Bar on the 

Klamath River (BBT) and Willow Creek on the Trinity River (WCT) in 1996 (Figure 32, page 

63, USFWS 1999). 
80 

0

5

10

15

20

55 65 75 85 95 105 115 125 135 145 155 165 175 185 195

0

5

10

15

20 N

u

m

b

er

1956

1992-1993

Midpoint of length group (cm TL)

Figure 20. Length frequency distribution of green sturgeon tagged in Arcata Bay in 1956 and 

1992-1993. 
81 

1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

0

2

4

6

8

10

12

Year

Catch

1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Year

GST:WST ratio

Figure 21. San Francisco Bay Study catch of green sturgeon in otter and midwater trawls.

Figure 22. Green sturgeon:white sturgeon ratio in otter and midwater trawl catches by the San 

Francisco Bay Study.
82 

1968 1972 1976 1980 1984 1988 1992 1996 2000

0

1

2

3

4

S

a

vl a

g

e/10

0

0

a

cre-fe

et

1968 1972 1976 1980 1984 1988 1992 1996 2000

0

1

2

3

4

Year

S

a

vl a

g

e

/10

0

0

a

cre-fe

et

State Fish Facilities

Federal Fish Facilities
83 

Figure 23. Estimated annual salvage of green sturgeon per 1000 acre-feet of water exported at 

the state and federal fish facilities in the south Sacramento-San Joaquin Delta.