On June 1^st trapping operations at Hatfield State Park were concluded for the season.  The traps sampled a total 111 of the 129 days from January 24^th to June 1^st.  A total of 414 Chinook were captured this season.  The first Chinook was captured on March 28, the last recorded catch of Chinook occurred on May 23^rd (Figure 1).  The peak catch of 104 Chinook occurred on April 25^th (Figure 2).  This day also had the largest catch of wild Chinook which accounted for 61 of the 104 fish captured.  The largest CWT catch (62 fish) and overall second largest catch of the season of 95 fish occurred on April 26^th.   Season total for wild and CWT Chinook was 191 and 223 fish, respectively.  Wild Chinook account for 46% of the total Chinook catch this season.

Figure 1. Picture of Chinook smolt (FL-55 mm) captured on May 23rd. [click on the photo for enlarged view]

Figure 2. Chart showing Chinook catch vs. flow at the Hatfield traps.

No trap efficiency tests were conducted during this sampling period.  Table 1 summarizes the results of the efficiency tests conducted during the season.  Availability of fish for efficiency testing was limited due to poor escapement results this season.     

Table 1. Marked fish releases conducted at Hatfield State Park to evaluate trap efficiency.

This season a total of 3,367 incidental fish, composed of 20 different identifiable species, were captured in the traps.  Of the 21 different species 14 are potential predators of juvenile salmonids, only 3 of the 14 are native to the Central Valley: Sacramento pikeminnow (Ptychocheilus lucius), prickly sculpin (Cottus asper) and riffle sculpin (Cottus gulosus), the other 11 are introduced.  Centrarchids (black bass and sunfish) compose 9 of the 11 and the other 2 are of the family Ictaluridae (catfish and bullheads). 

During this sampling period a total of six different types of incidental species were captured, spotted bass, largemouth bass, goldfish, hardhead, western Mosquitofish and numerous bass too small to identify to species (Figure 3).

            

Figure 3. Photo of  two juvenile bass (left) and numerous bass many of which were to small to identify to species (right) caught on May 29^th and 30^th, respectively. [click on the photo for enlarged view]

Environmental Data: 

Instantaneous water temperature measured at the Hatfield rotary screw trap ranged from 64°F to 75°F.  Instantaneous turbidity measured at Hatfield rotary screw trap ranged from 1.04 to 5.18 NTU.  During this sampling period flows at Snelling (MSN; RM 46) ranged from 253 to 277 cfs, and at Cressy (CRS; RM 27) from 304 to 334 cfs.  Hourly flows in Dry Creek (DSN; confluence at RM 31.5), which is a significant tributary to the Merced River, ranged from 0 to 1 cfs.