36 EIGHTH PACIFIC SCIENCE CONGRESS 



but there are still some features which suggest that this may not be 

 complete explanation. 



Internal Waves. 



Another characteristic of the B.C. inlets not previously described 

 is the existence of marked internal waves both at mid-depths and also 

 near the surface. The mid-depth internal waves have been observed 

 in most detail in the region of the temperature minimum at depths be- 

 tween 50 and 150 meters in series of bathy thermograms made for periods 

 up to 70 hours. They have periods of approximately 12 or 24 hours and 

 amplitudes up to 20 m., but it is as yet uncertain whether these waves 

 are progressive or standing in character. 



The most marked shallow internal waves have been observed in 

 Knight and Observatory Inlets in the boundary between the brackish 

 surface water and the deeper saline water. The depths of the boundaries 

 at the time were 5 and 8 m. respectively and the internal waves had 

 amplitudes as great as 8 m. and periods from 1.3 to 2.6 minutes. These 

 shallow internal waves are observed in the vicinity of the sills in these 

 inlets when the tide is turning to the flood. It is believed that they are 

 a consequence of instability in the flow associated with the considerable 

 velocity shear which exists at this time. 



Velocity Structure. 



A start had been made in obtaining vertical velocity profiles in 

 some of the inlets. The depth (650 m. or more) makes anchoring dif- 

 ficult but some preliminary results have been obtained. These confirm 

 the outward flow in the brackish layer, with up-inlet flow below this, 

 and considerable shear in the region of the halocline. Unfortunately 

 the tidal currents are superposed upon the estuarial flow and since their 

 detailed distribution with depth is not at all well understood, it has 

 not yet been possible to separate the estuarial components alone. 



Zoological Collections. 



During the 1951 survey trawling was carried out in shallow waters 

 in many inlets, while plankton hauls were made at regular intervals. 

 Over 1100 fish of 55 species representing 19 families were taken, cottids 

 (sculpins) and peuronectids (soles) being most common. No species not 

 previously reported in B.C. waters were taken but a number of uncom- 

 mon ones were observed and an extension in range of several varieties 

 was noted. 



Both phytoplankton and zooplankton collections were made but 

 only the latter have yet been examined. The total settling volume of 



