CALIFORNIA DEPARTMENT OF FISH AND GAME COMMENTS TO NMFS
REGARDING GREEN ST URGEON LISTING

Executive Summary

On December 14, 2001, in the Federal Regist er, 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 s ubstantial 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 wh ich we have access concerning green sturgeon
in California. We have made use of data fr om various units of CDFG and well as relevant published material, both primary and gray lite rature. We discuss green sturgeon range and distribution, migrations, size and ag e 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 si nce 1948; 2) fish facility salvage data from 1968 to present; 3) trawl, gill net, fyke trap, sein ing, and set-line catches fr om surveys starting as early as 1980; 4) juvenile catches at the Gle nn-Colusa Irrigation Dist rict 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 (U SFWS) of adult and young-of-the-year sturgeon observed in the vici nity of Red Bluff Diversion Dam on the
Sacramento River. For the Klamath River system, we present 1) se ining 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 Klamat h, Trinity, and Salmon rive rs as early as 1968.
Information on the Eel River and on other coastal bays and rivers is extremely limited. Onthe Eel River, we present reco rds 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 co nclusions 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 rate s are low (although based on meager data); that dams, with the excep tion of Red Bluff Dive rsion 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 Pr ogram 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 Protec tion Information Center, the Center for Biological Diversity, and WaterKeepers Northern California jointly submitted a petition to the National Marine Fisheries Service (N MFS) to list the green sturgeon ( Acipenser medirostris ) as either threatened or endangered under th e federal Endangered Species Act (ESA). The petitioners justify their request ba sed, generally, on the following assertions: 1) Green sturgeon have experienced a severe recent decline in overall abundance. An
article in Fisheries , an American Fisheries Societ y publication, described the green sturgeon as endangered and indi cated 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. Mo re former spawning populations have been extirpated in the past century than curren tly 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 a nd Sacramento spawning populations would be classified as separate Evolu tionarily Significant Units if adequate genetic information
were available. 4) The green sturgeon may have certain unique depensatory mortalit y factors that take an increasing percentage of progressively smaller populations, dooming them to
extinction. 5) Present fisheries (especially a commer cial fishery in the Columbia River and Washington coastal region and the developi ng tribal gill net fi shery on the Klamath River) continue to deplete a stock of large, ol d 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 stur geon occur in a region with no evidence of4
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, excep t white sturgeon, are considered to be threatened in one way or another. 7) The sport fishery slot limit in Californi a does not offer adequate protection to large and fecund female green sturgeon. On December 14, 2001, the National Marine Fisheries Service (N MFS) published its 90- day finding on the petition in the Federal Regist er. 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 gr een sturgeon to determine if the petitioned action is warranted. To this end, NMFS solicited information and co mments 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 info rmation to which we have access concerning green sturgeon in California. We have made use of data from various un its of CDFG and well as relevant published material, both primary and gray literature. We disc uss 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 da ta not available to the CDFG. These include researchers at the University of California , Davis (UCD) (e.g., genetic differentiation of populations, physiology, reproductiv e biology), the U.S. Fish and Wildlife Service (USFWS)
Fisheries Research Assistance Offices in Arcat a and Red Bluff (e.g., Klamath River harvest, spawning locations, and age stru cture; upper Sacramento River occurrence of juveniles and spawning areas), and the Klamath and Trinity River tribes (harvest and si ze and age structure). Also, the Interagency Ecological Program for th e 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 Migration5
Sacramento-San Joaquin System

Adults Information on adult green sturgeon distributi on and migration is ava ilable from the CDFG tagging program, from a CDFG telemetry study, a nd from incidental observations and anecdotal reports. Tagging - Although we have discovered some ta gging 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 con tinued intermittently since then, most recently by tagging in 2 successive years, skipping 2 years, th en tagging again for 2 years. This pattern is designed to provide the most reliable es timates of mortality rates and abundance. Sturgeon are captured in trammel nets in Sa n 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 r ecorded. Reported recove ries 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 be en tagged in the estuary (Table 1; Appendix A); 17 (7.3%) of these have been recove red, mostly from commercial fisheries (13) (Table 2). Two of the recoveri es 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 a nd probably also came from the es tuary. 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 gr een sturgeon (12) have come from commercial fisheries in Oregon (7) and Washington (5). Eigh t of these recoveries were from the Columbia River (or vicinity), mostly in late summer. Th ree recoveries were from the vicinity of Grays Harbor, Washington and one wa s from Winchester Bay, OR. In 1948 and 1949, apparently inci dental 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 was6
subsequently recovered: a 65-cm fish from Monter ey Bay, 197 days after being tagged (Table 2). These tagging data, although sp arse, indicate that legal-si zed green sturgeon found in San Pablo Bay in the fall make extensive ocean migrati ons and spend much of their lives in the ocean or in Oregon and Washington estuaries (prima rily the Columbia River and Grays Harbor estuaries). The recovery of one tagged fish fr om San Pablo Bay after 3 years at large suggests that some sub-adult green sturgeon remain in th e Sacramento-San Joaquin Estuary for extended periods or move back into the estuary after ye ars in the ocean. We know of no green sturgeon tagged in the Columbia River or other areas in Washington or Ore gon 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 sturge on. This 184-cm fish was tagged on March 7, 1991. It was only located once, 7 days after ta gging, at which time it had moved upstream to river kilometer (rkm) 107, above the mouth of th e 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 gree n sturgeon movements in the Sacramento River.
Incidental observati ons and anecdotal reports - U.S. Fish and Wildlife Service personnel observed sturgeon while electrofishi ng 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 st urgeon (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 stur geon. 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 Ca lifornia, Davis [UCD]; pers. comm.) found7
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’ de scriptions of catching green sturgeon in the Feather River. Subsequent c ontacts by CDFG of bait shops along the Feather River in spring 2000 yielded no information that st urgeon had been caught in that river recently. Possibly, green sturgeon only use (spawn in?) th e 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 av ailable from USFWS catches of young-of-the-year fish at Red Bluff Divers ion Dam, catches at the Glenn-Colusa Irrigation District fish screens, San Franci sco Bay Outflow Study otte r 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 ha ve been caught in traps at two sites in the upper Sacr amento 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 Ju ly 2000 at RBDD and from 1986 through 2001 at GCID. All sampling at RBDD was with rotary-s crew 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 pumpi ng plant; thus, sturgeon catches we re recorded over a longer time period. For purposes of these comments, we assumed th at larval and post-larv al sturgeon captured in this upper reach of the Sacramento Ri ver 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, in8
a 1994 letter to Nick Villa, CDFG; Gaines and Martin 2001). Sturgeon larvae first appear in RBDD catches from early May to ear ly July at lengths ranging from 24 to 31 mm FL. Timing of peak cat ches has varied annually, but has always occurred in either June or July (Figure 1). Migration of most young-of-t he-year fish past RBDD is over by the end of August. At this time, young-of-t he-year migrants have ranged from 32 to 70 mm FL (Gaines and Martin 2001). Sturge on 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 st urgeon 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, larv al and post-larval sturgeon have first appeared at GCID as early as Ma y 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 catch es of 34-36-mm larvae in October 1997, 1999, and 2000. Larger juvenile sturgeon (> 100 mm) have been caught in Ju ly 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). Catc h 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 a nd going downstream through South San Francisco Bay. It has captured only 61 juven ile sturgeon since it started in 1980. They have ranged in size from 20 to 112 cm TL and have been captured th roughout the estuary; however, the majority (42 fish) have been taken from Carquinez Strait upstr eam 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 Prot ection Study. These results were published in
1966 as CDFG Fish Bulletins 133 and 136. Gan ssle (1966) caught 34 juvenile green sturgeon9
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 (Rad tke 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 yea r-class strength of white sturgeon. The gear has included set and drift gi ll nets (1988-1989), otte r trawls (1989-1990) and baited set-lines (1991-2001). All gear was desi gned 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 Broa d Slough in 2000.) (Table 5) and 17 of those were caught in gill nets when they were fished in 1988-1989. The ju venile green sturgeon ra nged in size from 32 to 122 cm and were found throughout the sampling ar e that started in th e 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 indica tes that they occur th ere, either naturally or as the result of
reverse net flows in the centra l and south delta (Appendix D). Estimated salvage of green sturgeon is discussed further in ot her sections of these comments. Also associated with water exports from the south delta are observat ions of green sturgeon
in Kodiak seine catches in C lifton 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 (App endix E). It is likely that these fish are not trapped in Clifton Court Forebay, but can move in and out th rough 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 nets10
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 f yke traps. Gill nets caught 20 green sturgeon in 5 different years between 1989 and 2000; 15 of these were captured in 1 y ear (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 caugh t before 1990, when the fyke traps were moved from Clarksburg to Kni ghts 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 Pabl o Bay in recent years (G. Hough, FV Morningstar skipper, pers. comm.)

Klamath River System

Adults
The Klamath River is accessibl e 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 (M oyle and Yoshiyama 1992). Spawning probably
occurs in the immediate area of Ishi Pishi Fa lls, but young-of-the-year fish have not been confirmed upstream of Big Bar (Krkm 80) (U SFWS 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 ups tream of Trkm 40 (Healey 1973). Mature green sturgeon usually enter the Klamat h River in late March to mid-April with the peak migration in mid-April to mid-May. (USFW S 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 po rtion of the adult harves t occurs after August, especially in the estuary and lower 10 km of the river.

Juveniles Young-of-the-year (YOY) emigration from upriv er spawning areas in the Klamath-Trinity system, as measured by fyke nets in the Trinity River (Healey 1973) and rotary-screw traps in11
the Klamath River (USFWS 1998, 1 999) 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 st urgeon 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 stur geon 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 Oc tober 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 r ecorded, catch per seine haul ranged from 0.047 in 1984 to 0.472 in 1987 (Figure 3), suggesti ng 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. Unpublishe d 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 mi grants were of local origin.

Eel River

Adults Adult (1.5-2.0 m) green sturgeon were obser ved in the Eel River between rkm 100 and rkm 160 by CDFG biologists while conducting ot her surveys in 1995, 1996, and 1997. In 1995, sturgeon were observed during Apr il (1 fish), September (4), and November (1) and in 1996 and 1997, during August (1 fish each year). All but on e of these fish were in Humboldt County and12
were legally protected from captu re by the sturgeon fishery clos ure (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 du ring 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 thr ough fall sampling at McCann (rkm 76) during 1968-1970 and Fort Seward (rkm 109) during 1968 (Table 6). Limited length information indicates that j uvenile 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 stur geon 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 (Appe ndix G). Green sturgeon were again tagged in Arcata Bay in 1992 and 1993, apparently by CDFG a nd Humboldt State Univ ersity personnel.13
In both instances, fish were probably capture d in bottom trawls. We have no record of recaptures from any of these fish, so they pr ovide no information on green sturgeon movements or distribution other than to document the appa rent common occurrence of sub-adult and adult fish in Humboldt Bay. Other evidence of green stur geon 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 sturge on 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 gr een sturgeon in the Sacramento-San Joaquin System is available for fish captured during tagging, set-lining, gill nett ing, trawling, party boat sampling, larva sampling, striped bass tagging, and fr om catches at the Glenn Colusa Irrigation District intake and by th e USFWS at Red Bluff Diversion Dam. Most of these fish were not aged, but age of fish captured afte r their first year of life can be inferred from an age-length key (Table 7) developed from 150 aged fish colle cted 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 ha s 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 194814
(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 dur ing tagging great enough to warrant examining the size and age
structure - the latter with the constraint that th e available age-length key includes only fish age 9
and less and 120 cm and less and with the cavea t that green sturgeon are difficult to age. The size composition of the catch in these 3 ye ars 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 un likely 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 dist ributions provide no strong evid ence that green sturgeon produce strong year classes in wet years, as is the case with white stur geon (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 sa mpled 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-fre quency distributions. However, the USFWS has summarized some of thes e data in the form of weekly mean lengths from 1995 to 1998 (February 9, 1999 memorandum fr om P. Gaines, USFW S to P. Ward, CDFG) and median monthly length for 1995-2000 (Gaine s and Martin 2001). Unfortunately, the 1995-15
1998 data are described as fork length measur ements (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, s uggesting that young sturgeon are rearing and growing above RBDD before moving downstream. Glenn-Colusa Irrigati on District catches - Since 1988, CDFG personne l 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 (m odes 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 leng th in 1986-1993 to total length in 1996-2001; the length-measurement method in the inte rvening 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 c onsistent 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 RB DD, whereas sampling at RBDD captured only fish spawned above the dam. Perhaps, closur e of the dam gates on May 15 results in more protracted spawning below the da m (only early migrant, early sp awners 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 st urgeon is suggested by catches of 34-36-mm larvae in October 1997, 1999, and 2000. If data were av ailable, comparisons of length variability between sturgeon caught at RBDD and GCID migh t indicate whether a wider size range existed
at GCID. A potential problem with length data from ro tary-screw traps at both RBDD and GCID is the efficiency for small green sturgeon of g ear designed to capture juvenile chinook salmon. Because they sample near the surface, the trap s 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 sl ow 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 rang ed 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 re sults were published in
1966 as CDFG Fish Bulletins 133 and 136. Ganssl e (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 fo rk 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 (R adtke 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 ne ts, 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. Th is 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 gr een 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 signifi cantly 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, a nd Migration). None of the17
six green sturgeon caught in fyke traps were meas ured, but the 20 fish cau ght 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 (Fi gure 12) (USFWS 1983) and the other from catches in 1990-1993 (Figure 13) (Nakamoto and Ki sanuki 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. Le ngths of age 0 fish in the 1979-1982 age-length relationship (Figure 12) are a ma ximum of about 30 cm TL, wherea s 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) (U SFWS 1984). Most (90%) males were <187
cm and most females were >171 cm. Total lengths of green sturgeon harvested by th e tribal fisheries on the lower Klamath River changed little between 1980 and 1992, the only year s for which data are available (Table 9) (USFWS 1994). These data are not reliable as an indicator of si ze trends as they represent only catches near the mouth of the river, are only a sm all sample of all tribal harvest, were caught by different gear in some years, and seem to incl ude some fish from USFWS beach seining in the early years.
Additional information about the size of adu lt and subadult green sturgeon in the river is available from CDFG seining for salmon and steelh ead 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 this18

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 avai lable length-age information, thes e fish were probably between 1 and 15 years old. An increasi ng size distribution of the cat ch between 1979 and 1981 led the USFWS (1982) to hypothesize that they were samp ling a strong year class of Klamath system origin that was growing over time, implying that th ese were coastal migrants of local origin that were re-entering the Klamath River estu ary after spending time in the ocean. Beach seine catches of green sturgeon by th e CDFG from the upper estuary (Krkm 4 to 5), from August to early October, 1984-1990 were com posed 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 Ri ver 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 fi sh 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 trap s 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 co nsiderable growth upstream of th e trapping site. The latter is consistent with the interpreta tion 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 stur geon 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 fi sh tagged in 1992-1993 were significantly larger (mean = 131.1 cm TL) than those ta gged 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 oyste r 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 larg e green sturgeon were more vulnerable to the fishing tec hnique used in 1992-1993 than in 1956.
Habitat Use

Sacramento-San Joaquin System

Spawning
Based on information from catches of st urgeon eggs, larvae, and juveniles in the Sacramento River and data on white sturgeon, it app ears 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 gr een 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 da ytime sampling above Colusa in 1973 (Kohlhorst 1976), even though the nets were fished at Or d 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 di stinctly 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 gr een sturgeon larvae (D. Kohlhorst, CDFG, pers. comm.). 3. Sturgeon eggs collected on artificial subs trates between Knights Landing and Princeton (Schaffter 1997) were similar in morphology and co loration and were not consistent with size and coloration of green sturgeon eggs (R. Schaffter, CDFG, pers. comm.). 4. Adult green sturgeon have been observ ed below RBDD during electrofishing surveys there in April and May 1991, incl uding one dead fish for whic h identification was certain. However, a few adult white sturgeon, but no gree n sturgeon were observed the previous year, so identification of fish briefly seen in the water may be unreliable and depe ndent 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 (presuma bly green sturgeon) at both RBDD and GCID suggests that spawning is protracted and exte nds 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 st urgeon move above Prin ceton during spawning migrations (Schaffter 1997), yet many adult st urgeon are seen in the vicinity of RBDD.

Rearing Based on size and temporal distributions of young green sturgeon, it appears that many of21

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). Ca pture 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 fac ilities (Appendix D), and in Suis un and San Pablo bays (Ganssle 1966 and Figure 9) indicates that some fish r ear 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 te mporarily, after spending time in the ocean. The reason for their reappe arance in the estuary is unknown (see following
section on Sacramento-San Jo aquin 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 gr een 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, ba y 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 th e apparent movement of subadu lt 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 a ll 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 ni ne 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 (K rkm 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 ups tream 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 captu red. It is not known if green sturgeon also spawn below these trapping sites.

Rearing Coastal migrants - Green sturgeon in the size range of ag e 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 se ined in late summer a nd early fall in the upper, fresher portion of the estuary (Krkm 4-5). Thus, they probably only use the saline por tion of the estuary.

Larvae and Juveniles - As YOY green sturgeon have b een found both in the Salmon River (see Range and Distribution) and in seine catche s between rkm 4 and 5 (F igure 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 sturge on diet or feeding behavior in the Klamath River system. During 1980, stomachs from nine ma le and seven female adult sturgeon captured
in the Klamath River below We itchpec 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 sim ilar to those in the Klamath River, the entire river to the estuary should be cons idered juvenile rearing habitat. No information is available on green sturgeon diet or feeding behavi or in the Eel River.

Other Coastal Rivers and Bays

Not much can be said about green sturgeon hab itat use in other coastal rivers and bays other than that they occur in some of these areas, such as Arcata Bay (see previ ous 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 sturge on habitat use in the ocean off California. They have been incidently caught in commercial fisheries in near shore 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

Tagging24

Recaptures of tagged white stur geon in the trammel nets (tagged green sturgeon have never been recaptured in the trammel nets) are record ed and used, in conjunc tion with the number tagged, to estimate abundance in previous years usi ng 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, thei r abundance is estimated by multiplying white sturgeon abundance estimates by the ratio of gree n sturgeon catch to whit e 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 a nd 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 st urgeon 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 stur geon 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 vari ability probably has as much to do with sampling error in capturing the relatively rare gr een sturgeon as it does to actual annual changes
in relative abundance. This is further evid ence that the green sturgeon population estimates
should be viewed with caution. As an aside, and consistent w ith the expectation that larger gr een 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 tagg ing catches has generally been gr eater than for the larger fish (Table 10). Ratios for these younger fish ha ve ranged from 0.011 in 1991 and 1993 to 1.661 in
1974. Green sturgeon abundance estimates have vari ed substantially in the Sacramento-San Joaquin Estuary (Table 10). Aside from th e 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 lo west was 198 in 1954. Even without the low25

estimate in 1954 and the high estimate in 2001, there is no tre nd in these data (F 1,10 = 1.49, p >0.25), so they provide no evidence for a gree n sturgeon population declin e in the SacramentoSan Joaquin Estuary. Continued high green st urgeon tagging catch and estimated abundance in
2002 would be consistent with th e production of strong year classe s in the wet years of the 1990s and, possibly, the benefits of current operation of Red Blu ff Diversion Dam.

Juvenile Surveys Juvenile monitoring surveys designed to inde x 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 juve nile 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 du ring this sampling (Table 5). Most of the juveniles (16) were captured in gill nets when th at gear was fished from 1988 to 1990. An otter trawl caught one juvenile in 1989 and the set-line s caught two juveniles and two older fish in 1998 and 2000. The higher catches in the early year s of this survey are probably the result of greater green sturgeon vulnerability to the gill nets used then th an 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 stur geon 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 va ried between 0 and 9 thereafter. Annual catches did not exhibit a statistically significant time trend (F 1,20 = 2.97, p = 0.10). Monthly catches were too low to
ascertain seasonal trends in abundance. For comparison, the Bay Study has caught 886 wh ite sturgeon, for an overall ratio of 0.069 green sturgeon:1 white sturgeon. This ratio has va ried from 0 in 4 years when no green sturgeon were caught to 0.600 in 1 994 (Figure 22, Appendix K).26

Salvage - State water exports from the south delt a 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). Es timated 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, estimat ed 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 (F 1,32 = 2.53, p >0.10), even though highest catches were in the early years of st ate fish facilities operation. Federal exports from the delta began in 1951, but no green sturgeon were recorded at the federal fish facility un til March 1981, when it was estimated th at 75 green sturgeon were salvaged (Appendix L). Federal fish facili ty estimated green sturgeon salv age/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 wa s 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 (F 1,19 = 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 w ith 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 hour s 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 fact ors 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 System27

There are no population estimates available for adult green stur geon 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 sturge on harvest. We do not have data to assess changes in harvest as an indicato r of adult population tre nds, 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 produ ction 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 obs erved 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 info rmation about green sturgeon populat ion 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 ar e 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 af ter tagging are used to estimate annual harvest rate. Since 1967, all sturgeon tags have offered a re ward to fishers returni ng 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 ar e 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 ta gged and even fewer are reported recaptured, estimated harvest rate for most tagging years is ze ro (Table 12). The exceptions to this are 1948, 1979, 1984, and 1985, when 1, 2, 1, and 1 tags were repor ted 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 whic h 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 taggi ng in the fall; they are in the ocean. Multiplying annual green sturgeon population es timates 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 for29

tribal catches on the Klamath Ri ver below Weitchpec and the lower 26 km of the Trinity River. These statistics are included as Appendix 2 of the listing petition and repr oduced here as Table 11. Partial comparison with the sour ce 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 th e fish) were caught by non-Indians” (USFWS 1981:86). There have been other unexplained revisions and correc tions of Klamath harvest data during the 1980s, but other cha nges are minor (USFWS 1994). Estimated harvest in 1980 and 1981 was substantially higher than in other years, but even without thos e years, the decreasing trend in harvest is statistically significant (F 1,16 = 6.18, p <0.05). These data do not account for effort, so trend in catch per effort is unknown a nd 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 av ailable from the Eel Rive r. Most of the Eel River system is in Humboldt County and thus is cl osed to harvest of stur geon, 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 occu r in these areas, as evidenced by the report of two green sturgeon captured by halibut gear in Tomales Bay in A ugust 1993 (Knutson, CDFG, pers. comm.), over 20 fish (including several that were legal sized) in the surf off Pacifica on one30

day in May 1995 (J. Klinger, Paci fica Tribune, pers. comm.) and trawl catches in Arcata Bay (Appendix G). Commercial catche s in the ocean and bays may re sult is some mortality even though green sturgeon are not the target of th ese fishing efforts and must be released.

Habitat Impacts

Sacramento-San Joaquin System

Major historical changes that likely have negatively impact ed green sturgeon have occurred in the Sacramento-San Joaquin system, including c onstruction of dams on al most all rivers, filling of the bays, altered hydrology, diversions from th e 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 pro cess to provide additional and more reliable water supplies while also improving conditions for fish and wildlif e in the estuary and its tributaries, increased water storage in the Sacramento River basin has been proposed. This c ould 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 a ltering the hydrology of the river above Hamilton City. Specifically, flows could be reduced downs tream of Keswick or be low the intake for the pumped storage during part of the period of upstr eam 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 flow s and cooler temperatur es during the summer incubation and rearing period. The extent of de triment 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, improveme nts 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 a bove the dam, even continuation of present operations, which has been shown to result in substantial spawning ups tream of the dam. Increasing the period when the dam gates are ra ised 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 Bonnevi lle Dam on the Columbia River, which passes sturgeon successfully.

Glenn-Colusa Irrigation District To improve the efficiency of the GCID dive rsion by providing higher water levels in the intake channel, a weir across the Sacramento Ri ver 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 move ment 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 resu lt in increased mortalit y of juvenile sturgeon.

Water Diversions Aside from the proposed pumped storage rese rvoir(s) on the west side of the Sacramento Valley, no additional diversions from the Sacram ento River above Sacramento are proposed in the near future. However, numerous diversions ex ist 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 juveni le sturgeon in these agricultur al diversions has not been32

documented, it is likely that losses occur, especially as most dive rsion intakes are near the bottom and sturgeon larvae are demersal. Present scre en technology is probably not as effective for sturgeon as for salmonids. Information on white st urgeon behavior in relati on to fish screens is available from studies done at UCD and at experi mental facilities at Hood in the late 1970s and early 1980s.

Water Temperature Impacts of possible changes in water temperatur e 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 th e result of release of warmed water from Thermalito Afterbay. This may be one reason neither gr een nor white sturgeon are found in the river in low-flow years. It is not expected that water temperatures wi ll become more unfavorable in the near future.

Water Exports from the Delta We have already described the fact that vary ing numbers of green st urgeon are salvaged at
the state and federal fish facilities in the south delta and that subadult gr een sturgeon have been found in seining surveys in Clifton Court Foreba y. As export rates and through-delta movement of water increases in the future, the number of green sturgeon sa lvaged may increase. However, for white sturgeon, although year-class strength is re lated to freshwater flow s in late winter and spring, it is not related to the volum e of water exported from the delta. A proposal to construct another diversion poi nt on the Sacramento River near Hood to transport water into Snodgrass Sl ough and ultimately to the pumpi ng 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 dive rsion might entrain addi tional juvenile green sturgeon (beyond the number that now enter the Delta Cross Cha nnel 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 adul ts to the downstream side of the screen through Snodgrass Slough33

and the need to provide passage for them th rough or over the screen. The technology for doing this may not exist.

Bay Filling Filling of San Francisco Bay has historically reduced foragi ng areas for sturgeon, but this activity has been curtailed in recent years. Ho wever, plans to add runway capacity to San Francisco International Airport will re sult in filling several square ki lometers of the bay. This is a contentious issue and may not occur, but if it do es, additional sturgeon fo raging habitat will be lost without assurance that mitigation will be adequate.

Exotic Species Introductions Introduction of exotic species is an ongoing problem in the es tuary. The most likely impact on green sturgeon of these introductions is throu gh 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 sp ecies of sturgeon. However, mitte n crabs have had a major impact on the sturgeon fishery, as they ar e 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 th e estuary (Ganssle 1966, Radt ke 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 qualit y in the Sacramento-San Joaquin system, the influence of toxicants, especially their chronic effects on surv ival 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 stur geon in the past have contained high PCB loads (Kohlhorst 1980), although more re cent data showing much lowe r contamination suggest these earlier results may have been erroneous (D. Kohlhorst, CDFG , pers. comm.; unpublished CDFG data). White sturgeon in the estuary do accumula te selenium, but tissue concentrations have varied among years without trend an d do not seem to be related to fish size (White et al. 1989). The difference in distribution of green and wh ite sturgeon (ocean migrants vs. estuarine inhabitants) probably makes green sturgeon less vulnerabl e than white sturgeon to bioaccumulation of contaminants found in the estuary.

Klamath River System

Two important habitat characteristics critic al to successful green sturgeon spawning and rearing in the Klamath River system are main tenance of suitable spawning habitats and maintenance of suitable water temperature, at least during egg incubati on and larva rearing. Deng (2000) suggested that green sturgeon eggs, because of there relative lack of adhesiveness, depend on being trapped in crevic es in bedrock or under gravel. Larvae younger than 6 days posthatch show very limited mob ility and older larvae exhibit strong negative phototaxis, behavior which would al low them to develop within relatively short, high gradient streams (ibid). Thus, the introduction of finer substrate material, espe cially covering bedrock, cobble, or coarse gravel, is proba bly detrimental to green sturgeon. Cool water temperatures are also probably important to green sturgeon egg and larva development. Optimal temperatures for egg su rvival and development of other species of sturgeon is about 14 to 17 o C and egg and larva survival decrea sing rapidly at higher temperatures (Wang et al. 1985).35

Past logging practices have contributed to se dimentation in the Klamath River system. The loss of sturgeon spawning habitat in the South Fo rk Trinity River is largely the result of road building and clear-cutting. Logging practices are mu ch 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 st urgeon 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 affect ed 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 indus trial and municipal wa ste and restriction on dumping such waste into bays, conditions for oc ean 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 hi storically contained gr een sturgeon may inhibit
recolonization of these areas.

Conservation Actions

Sacramento-San Joaquin System

Angling Regulations36

Both species of sturgeon are now protected by sport angling regulations (no commercial harvest is permitted) that allow the year-round ta ke of one fish per day between 117 and 183 cm TL. In addition, a closure of central San Fr ancisco 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 th at they spend most of this period in the ocean where they are infrequently caught. No changes in angling regulations are contempl ated at this time. B ecause legal-sized green sturgeon are easily distinguished from white st urgeon and are a very minor component of the sport fishery, closure of the estuary and its tribut aries to green sturgeon fi shing 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 vulne rable to the fishery, such as th e delta to San Pablo Bay area in late winter and the upper Sacramento River durin g the spawning migration. The trophy status of white sturgeon and the conseque nt incentive for reta ining 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 Proj ect Improvement Act (CVPIA) implements the CVPIA goal to double natural production of anad romous fishes (including sturgeon) in the Central Valley by this year (2002). Tools availa ble include enhancing st ream flows, relocating and screening diversions, and using up to 800,000 acr e-feet of Central Vall ey Project yield for
fish and wildlife restoration. We are not aware of any AFRP actions sp ecifically designed to37

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 th e green sturgeon by re storing its population
distribution and abundance to hist orical levels. The CALFED Ecosystem Restoration Program Plan (ERPP) addresses some of the majo r factors limiting the green sturgeon population, including adequate stream flows for attracting adults to spawni ng areas in rivers, transporting young to nursery areas, illegal and legal harvest, and entrainment into water diversions. The
ERPP calls for actions that rest ore ecological processes, restor e 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 th e 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 bene ficial actions include re storing 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 fo r eliminating migration barriers such as diversion dams, reducing stra nding 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 he alth and reproduction. A new stat e-of-the-art fish screen and fish salvage facility for the State Water Proj ect 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 re gulated 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 furt her 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 includ ing Ishi Pishi Falls from April 1 through July 15. In 1990, a maximum size limit of 183 cm was in stituted and the minimum size limit was
increased in 5-cm annual increments until it r eached 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 j uvenile 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 Ri ver downstream of Benbow Dam.

Enforcement Activities CDFG enforcement personnel feel that enforcem ent 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 No rte and Humboldt counties has been prohibited39

since 1993. These closed waters include the Smith River, Humboldt and Ar cata bays, and all tidal sections of rivers, creeks, and bays. From Me ndocino County south, gree n 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 a bout the status of green sturgeon in California, based on available information, and generally organi zed 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 (populati on 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 unr eliable species identification (state and federal fish facility salvage), or lack data to correct fo r temporal changes in effort (tribal harvest in the Klamath River system). Only two measures e xhibit a significant decr easing trend over their period of record and these are probably the least reliable abundance indicators (salvage records and tribal harvest). Other abunda nce measures exhibit no time trend. In this regard, the statement that the green sturgeon has suffere d 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 s ubstantiated 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 i ndicated that he had written the sections on sturgeon in Musick et al. ( 2000) and that his respons e had been “read and approved” by Dr. Musick. His response is as follows: “We would like to apologize for the missi ng citations, and incorrect figure in the40

section on green sturgeon (which is also incorr ect 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, incl uding green, suffered approximately an 88% decline in California, as inferred from commerci al catch rates (Cech 199 2). Similar declines occurred in other areas (Hart 1973). Early commercial fisherie s 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 te nuous estimation, howev er, 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 th e article that data are needed for precise determination of
status.” Hart (1973) presents no information con cerning green sturgeon a bundance trends, although he does show commercial harvest figure for white sturgeon in the Fraser River. Cech (1992) presents sturgeon party boat catc h figures during a period of declin ing party boat fishing effort in his article on white sturgeon.

Green sturgeon distribution has been restricted - Restrictions in gr een sturgeon distribution mostly would occur as the resu lt of loss of spawning habitat, either through dam building, sedimentation, or degradation of water quality (including temperature ch anges). There is no
evidence that their marine habitat has been di minished, although histor ically, 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 spaw ning habitat in the South Fork Trinity River and the Eel River system due to anthropomorphic changes and natural events that, in combina tion, increased sedimentation. Ho wever, 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 Rive rs have barriers to upstream mi gration 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 spawni ng 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 gr een 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 th e 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, ha ve come from the know n 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 constructe d 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 th e early 1990s, suggest that they historically spawned above Shasta Dam. It is, therefore, surprising that only wh ite sturgeon were ever observed in Lake Shasta (Fisk 1963).

Exploitation presently threatens green sturgeon - The two areas of great est green sturgeon harvest are the Klamath River and estuaries and bays in Oregon and Washington. While numerical harvest estimates by the tribal fisheries in th e Klamath River are available, we have no information concerning effort, so tr ends in catch per effort cannot ad equately be explored. As the important statistic is harvest ra te (fraction of the population harv ested 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 to42

7.7% and almost all of that harvest was in Or egon and Washington. Becau se few green sturgeon are tagged in most years, tag recaptures by fisher s 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% w ill 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 re gulations allow only sport fishing for green sturgeon. Beside s restrictive size and creel lim its, sturgeon angling is prohibited in all areas of the Klamath River system inhabited by green sturgeon and in mo st 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, alt hough 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 ma rine resources and their utiliz ation. 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 fish ery. California Department of Fish and Game, Inland Fisheries Administrative Report 63-12. Gaines, P.D. and C.D. Martin. 2001 (draft). Abu ndance and seasonal, spatia l and diel distribution patterns of juvenile salmonid pa ssing the Red Bluff Diversion Da m, 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. Fi sheries Research Board of Canada, Bulletin 180:82-
84. Healey, T.P. 1973. Studies of steelhead a nd salmon emigration in the Trinity River.
Anadromous Fisheries Branch Administrative Re port 73-1. California Department of Fish and Game, Sacramento, California. Hopelain, J.S. 1988. A four-year summary of se ining/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 Depa rtment 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. Ca lifornia Fish and Game 62:32-4047

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. Botsfor d, J.S. Brennan, and G.M. Cailliet. 1991. Aspects of the structure and dynamics of an exploited centr al California populati on of white sturgeon (Acipenser transmontanus). Pages 277-293 in: P. Willot, editor. Acipenser: Actes du premier colloque internati onal sur l’esturgeon. CEMAGREF, Bordeaux, France. Moyle, P.B, P.J. Foley and R.M. Yosh iyama. 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 Aqua tic Biota. The California Policy Seminar, University of California 1992, pp 69-80. Musick, J.A. and 17 others. 2000. Marine, estuarin e, 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 Klamat h River Green Sturgeon ( Acipenser medirostris ). U. S. Fish and Wildlife Serv ice, Klamath River Fishery Resource Office, Arcata, California. Puckett, L.K. 1976. Observations on the downstr eam 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, j uvenile sturgeon, and starry flounder in the Sacramento-San Joaquin Delta with obse rvations on food of sturgeon. Pages 115-129 in : J.L. Turner and D.W. Kelley, compilers. Ecol ogical 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 mi grations 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 Investigation48

Program. Annual Report 1980. Arcata, California.
USFWS. 1982. Klamath River fi sheries investigation program , Annual Report - 1981. Arcata
California.
USFWS. 1983. Klamath River fi sheries investigation program , Annual Report - 1982. Arcata
California.
USFWS. 1984. Klamath River fi sheries investigation program , Annual Report - 1983. Arcata
California.
USFWS. 1985. Klamath River fi sheries investigation program , Annual Report - 1984. Arcata
California.
USFWS. 1988. Klamath River Fisheries Asse ssment Program, Annual Report 1987. Arcata,
California.
USFWS. 1989. Klamath River Fisheries Asse ssment 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 Asse ssment Program, Annual Report 1992. Arcata,
California.
USFWS. 1998. Klamath River Fisheries Asse ssment Program, Annual Report 1995. Arcata,
California.
USFWS. 1999. Klamath River Fisheries Asse ssment 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 Publis hers, 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 Depa rtment 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 27550

Table 2. Recovery information for green stur geon 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 Monter ey Bay, CA Commercial 197 27-Sep-54 130 28-Aug-58 Columbia Ri ver, WA Commercial gill net 1431 29-Sep-54 104 4-Dec-55 Columbia Ri ver, 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 Gray s Harbor, WA Commercial 653 15-Oct-67 a 114-127 a 20-Sep-68 Columbia Ri ver, OR Commercial 341 15-Oct-67 a 114-127 a 17-Aug-70 Columbia Rive r, OR Commercial 1037 15-Oct-67 a 114-127 a 1-Jan-71 San Pablo Bay, CA Sport 1174 27-Oct-67 117 23-Dec-67 Monterey Ba y, 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 Ha rbor, 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 Ri ver, WA Commercial gill net 668 9-Sep-85 188 30-Jul-86 Columbia Ri ver, 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 le ngth 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 Irri gation 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.

Ma y June Jul y Yea r Mean S.D. Ran g e N Mean S.D. Ran g e N Mean S.D. Ran g e 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

Au g us t Se p te m b e r Octobe r Yea r Mean S.D. Ran g e N Mean S.D. Ran g e N Mean S.D. Ran g e 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 28 152

Table 4. Month and location of juvenile green sturgeon catches by San Francisco Bay Outflow Study otter and midwater traw l 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 12253

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 0 a 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 co llected 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 1.00054

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 devia tion, 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 - 23855

Table 10. Sturgeon catch during tagg ing, ratios of green to white stur geon 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 2001 a 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 catches56

Table 11. Estimated harvest of green sturgeon in th e 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 Yurok 2 Hoopa 3 Karuk 4 Poaching 5 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 va riable and inconsistent sampling efforts based on voluntered data. b Some Yurok harvest occurs prior to a nnual monitoring activiti es of the USFWS.
c USFWS data onlv available from 1985. Available harves t estimates are biased lo w by variable and inconsistent sampling effort based on volunteered data. d Karuk harvest is not mo nitored by the USFWS.
e Illegal snag harvest occurred at Coon Creek Falls after 1977, where a debris slide created a migration obstacle.5756

Table 12. Annual estimates of harvest rate and catch for green sturgeon tagged in the Sacramento-San Joaquin Estuary.

Year Tagged 1 st -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 0.022 a

a Excluding 2001, for which 1 st year returns are not complete.57

Figure 1. Monthly catch per acre-foot and median total length ofsturgeon 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
Y ea r N u m b e r o f S t u r g e o n

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

S t u r g e o n C a t c h p e r S e i n e H a u l

Figure 3. Annual catch per sein e haul of green sturgeon in the Klamath River estuary, 1984- 1990.60

Figure 4. Total length frequencies of green sturgeon cap tured 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 e r

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

N u m b e r

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

W BN BN BN

WW

W W W W W

W BN AN AN D

D C

C C62



# D R A F T

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

0 1 2 3 4 5

0 1 2 3 4 5 6 7

0 10 20 30 40

0 20 40 60 80 100 120 140

0 50 100 150 200 250 300 350

0 20 40 60 80 100 120

0 20 40 60 80 100 120

0 10 20 30 40 50 60 70 80

0 2 4 6 8 10 12 14 1988

1990

1991

1992

1993

1996

1997

1998

2000

2001

Midpoint of length group (cm) N u m b e r o f s t u r g e o n

18 23 28 33 38 43 48 53 58 63 68 73 78 83 88 93 98 0 2 4 6 8 1064

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 individu al 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 t h 

## 1991 1992 1993 1996 1997 1999 2000 200166

Figure 8. Monthly mean lengths of sturgeon <1 00 mm caught by the Glenn-Colusa Irrigation District rotary-screw trap from 1991 to 2001. Y ears with <3 months data and months with only 1 fish measured are excluded. Length measur ements 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 e r

Figure 9. Length frequency of green sturgeon ca ught in otter and midwater trawls by the San Francisco Bay Outflow Study from 1980 to 2001.68

Figure 10. Length frequency dist ribution of green sturgeon ca ught 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 e r 

### Gill net Otter trawl69



### 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 20 N u m b e r 

### State Fish Facilities

Federal Fish Facilities

Midpoint of length group (cm FL)70

Figure 11. Length frequency distribution of green sturgeon collect ed 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 st urgeon 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 fo r green sturgeon from the Klamath River, 1990-1993 (Figure 4, page 10, Nakamoto and Kisanuki 1995).73

Figure 14. Combined length frequency distributio n of Klamath River adult male and female green sturgeon captured during 1980-1983 by beach seine, gill net and ho ok 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) N u m b e r o f s t u r g e o n

Figure 15. Length frequency of gr een sturgeon seined in the Kl amath River estuary, May 17 to August 1, 1977. Method of measurement (for k or total length) was not recorded.7576

Figure 16. Length frequency distributions of green sturgeon captured by beach seine and gill net in the Klamath River estuary, 1979-1 984 (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 N u m b e r o f S t u r g e o n

0 10 20 30

Figure 17. Length frequency of j uvenile 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 3078

0 5 10 15

N u m b e r o f S t u r g e o n July

Aug

Sep

51 76 102 127 152 178 203 229 254 Total Length -- mm

Figure 18. Length by month of YO Y 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-s crew 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 e r 

## 1956

1992-1993

Midpoint of length group (cm TL)
Figure 20. Length frequency dist ribution of green sturgeon ta gged 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



### YearCatch

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

YearGST: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 l v a g e / 1 0 0 0 a c r e - f e e t

1968 1972 1976 1980 1984 1988 1992 1996 2000 0 1 2 3 4



### Year S a l v a g e / 1 0 0 0 a c r e - f e e t 

## State Fish Facilities

Federal Fish Facilities83

Figure 23. Estimated annual salvage of green st urgeon per 1000 acre-feet of water exported at the state and federal fish facilities in the south Sacramento-San Joaquin Delta.