State of California Department of Fish and Game

M e m o r a n d u m

Date: October 5, 2011 To: Carl Wilcox Regional Manager, Region 3 California Dept of Fish and Game

From: Randall Baxter Senior Biologist California Dept of Fish and Game

Subject: Fall Midwater Trawl September fish abundance and distribution

The 2011 September Fall Midwater Trawl (FMWT) survey was conducted from September 6 through September 20, 2011. We report total catch from index stations and September abundance index by species and plot September abundance indices for all years for comparison (Figures 1-5). Species distributions are reported as total monthly catch by region. The September indices reported represent the 1st of the 4 monthly indices that will contribute to the annual FMWT indices. The annual FMWT indices are used to monitor species abundance trends through time.

Delta Smelt Forty were collected in September for a monthly index of 50, which represents a large increase from last year’s index of 6 (Figure 1). The September index was already higher than the annual abundance indices since 2005, and higher than September indices for all the POD years (2002-2010).

Delta smelt were collected at index stations in (catch=5), (16), Honker Bay (17), and the Confluence (2). Two delta smelt were collected at a non-index station in Cache Slough.

Age-0 Striped Bass One hundred two age-0 striped bass were collected in September for an index of 112, a large increase from last year’s index of 16 (Figure 2). This monthly index was higher than September indices during all the POD years (2002-2010), except the wet-year 2006.

Age-0 striped bass were collected at index stations in Carquinez Strait (7), Suisun Bay (27), Grizzly Bay (34), Montezuma Slough (5), Honker Bay (10), the Confluence (17), and lower (2). Three additional age-0 striped bass were collected at 2 non-index stations in Cache Slough.

Longfin Smelt Twenty-eight longfin smelt were collected in September for an index of 68. The 2011 September index increased substantially from the past four years’ September indices (Figure 3). Longfin smelt were collected in (9), Carquinez Strait (1), Suisun Bay (17), and Grizzly Bay (1).

Threadfin Shad Forty-eight threadfin shad were collected in September for an index of 67. The 2011 September index almost doubled from last year’s index of 37 (Figure 4), but was the fourth lowest in FMWT history.

Threadfin shad were collected in Suisun Bay (1), Honker Bay (8), the Confluence (3), lower Sacramento River (4), and South Delta (32). Five-hundred-sixty-nine threadfin shad were collected at non-index stations in Cache Slough (174) and the Sacramento Deep Water Ship Channel (395).

American Shad American shad was the most abundant and broadly distributed pelagic fish in September. Three hundred six American shad were collected in September for an index of 413. The 2011 September index more than tripled last year’s index of 130 and represents a substantial increase compared to indices since 2006 (Figure 5); however, it remains only half of the average September abundance index.

American shad were collected in every region sampled: San Pablo Bay (24), (1), Carquinez Strait (26), Suisun Bay (81), Grizzly Bay (6), Montezuma Slough (39), Honker Bay (77), the Confluence (31), lower Sacramento River (18), lower (2), and the South Delta (1). Two-hundred-one American shad were also collected at non-index stations in the Napa River (1), Cache Slough (83), Sacramento Deep Water Ship Channel (116), and the Mokelumne River (1).

cc: DFG Marty Gingras, Supervising Biologist Bob Fujimura, Senior Biologist Kathy Hieb, Senior Biologist

742 572 430 400 350 300 250 200 50 Index 15 3 9 1 150 20 26 33 2 6 100 50 No index No index 0 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02 04 06 08 10 Year Figure 1 FMWT September abundance indices of delta smelt.

11941 3992 4000 3500 3000 2500 2000 Index 1500 18 16 236 57 16 34 9 112 1000 40 32 500 No index No index 0 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02 04 06 08 10 Year Figure 2 FMWT September abundance indices of age-0 striped bass.

35797 7898 15484 15233 5430 3000

2500

2000 1563

Index 1500 127 44 1000 0 2 10 1 2 0 68 500 No index No index 0 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02 04 06 08 10 Year Figure 3 FMWT September abundance indices of longfin smelt.

7000 6000 5000 4000

Index 748 287 3000 137 610 1852 2000 59 37 80 2 67 1000 No index No index 0 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02 04 06 08 10 Year Figure 4 FMWT September abundance indices of threadfin shad. 2245 3246 3345 2000

1119 1600 826 1200 680 413

372 130 Index 800 123 81 400 14 No index 0 No index 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02 04 06 08 10 Year Figure 5 FMWT September abundance indices of American shad.