24 CALIFORNIA FISH AND GAME 



Pacific Coast Eelgrass Conditions, 1941-1942 



Summaries of the depletion of eelgrass on the Pacific Coast and 

 its suspected cause were provided by Mnffitt and Cottam (1941), Mof- 

 fitt (1941) and by Dr. C. E. Renn (1942). These reports dealt with 

 the depletion from the time it was first noted in 1940 until the summer 

 of 1941. Observers continued, as much as they were able, to check 

 upon the condition of local eelgrass stands during the autumn and 

 winter of 1941 and in the spring of 1942. Due to the war, however, 

 little information has been secured since the last brant census was 

 taken in February, 1942. 



The conclusion that the writer has reached from study of these 

 reports, from personal investigations in Tomales Bay, California, last 

 winter, and from the results, mentioned beyond, of Dr. Renn's exami- 

 nations of Oregon and California eelgrass samples, is that the disease, 

 Labyrinthula, must be present in a mild form more or less all along 

 the Pacific Coast. Reports of the abundance and appearance of eel- 

 grass in several California bays in February, 1942, indicated in most 

 cases improvement had been made over the previous year. Yet in some 

 instances both the appearance of the eelgrass and Dr. Renn's exami- 

 nations of samples collected from the same localities, indicated that 

 Labyrinthula was still present. It seems that either the type of Laby- 

 rinthula infecting the Pacific Coast eelgrass is a milder form than that 

 which almost completely destroyed the plant on the Atlantic Coast 

 about 10 years ago ; or that the strain or variety of eelgrass inhabiting 

 our waters is much more resistant to this organism. 



Inspection of eelgrass plants in Humboldt Bay by Warden Werder 

 in February, 1942, indicated that normal conditions obtained. Dr. 

 Renn examined samples collected in South Humboldt Bay on February 

 10, 1942, for Labyrinthula, and reported negative results. The behavior 

 of brant in Humboldt Bay last Winter and this Spring indicated con- 

 siderable increase in the quantity of eelgrass since the previous year. 

 On April 25, 1942, John M. Davis of Eureka wrote that while brant 

 were late to arrive at Humboldt Bay the previous winter, normal num- 

 bers seemed to be present by March. Up to April, he stated, he had not 

 observed a single brant feeding in the fresh-water fields, where the year 

 before they were frequently noted after midwinter. These observations 

 indicate that sufficient natural food, eelgrass, was present in Humboldt 

 Bay last Winter to support the number of brant present. 



Warden Laws collected samples of eelgrass in Bodega Bay on 

 February 10, 1942, which Dr. Renn later examined and found to be 

 infected by Labyrinthula. Laws noted little or no improvement in the 

 local eelgrass stands over the previous year. It seems that the reduced 

 quantity of the plant in this bay may be responsible for the small num- 

 ber of brant recorded by the census. 



The writer visited Tomales Bay on September 22, 1941. for the 

 purpose of inspecting the eelgrass and collecting samples of it, The 

 same area was covered in which on July 16, 1941, Cottam and Moffitt 

 (1941) had found plants showing the characteristic appearances of 

 Labyrinthula infection. In September, however, careful search failed 

 to reveal a single plant with any indication that Labyrinthula was 

 present. Furthermore, samples collected at that time and later exam- 

 ined microscopically failed to indicate presence of the disease. All of 



