Surface-to-Bottom Pot Fishing 

 for Pandalid Shrimp 



By 



LOUIS BARR, Fishery Biologist, and ROLAND McBRIDE, Biological Technician 



Bureau of Commercial Fisheries Biological Laboratory 

 Auke Bay, Alaska 99821 



ABSTRACT 



Baited shrimp pots were used to studythe seasonal and diel changes in vertical 

 distributions of several species of pandalid shrimp (primarily Pandalus borealis, P. 

 goniurus, and P. hypsinotus) in Kachemak Bay, Alaska. This method has good 

 potential for sampling shrimp populations in untrawlable areas. 



INTRODUCTION 



Shrimp of the family Pandalidae are gen- 

 erally captured on, or immediately above, the 

 bottom by trawling and pot fishing. Trawling, 

 which is the more common method, has been 

 used in Europe (Hjort and Ruud, 1938; Allen, 

 1963) and on North America's east coast 

 (Scattergood, 1952; Dow, 1963) and west coast 

 (Hynes, 1929; Harry, 1964). The other common 

 method, pot fishing, has been used in the 

 British Isles (Davis, 1958), Washington State 

 (Westley, personal communication), British 

 Columbia (Butler, 1964), and Alaska (Ellson 

 and Livingstone, 1952; Ronholt, 1963; Harry, 

 1964). Additional methods, used less fre- 

 quently, include: bag (or hoop) nets, which 

 were fished for Pandalus borealis in Dram's 

 Fjord, Norway, during the 1800's (Hjort and 

 Ruud, 1938); kype (or hose) nets, a type of 

 fixed gear, which was occasionally used to take 

 P_. montagui in British estuaries (Matthews, 

 1934--cited by Mistakidis, 1957); and beach 

 seines, 1 which were used in the early shrimp 

 fishery of Puget Sound (Smith, 1937). 



Pandalid shrimp have been caught occa- 

 sionally at midwater depths. For example, 

 they were taken incidentally during exploratory 

 fishing with midwater trawls (Tegelberg and 

 Smith, 1957; Aron, 1959; Rathjen and Fahlen, 

 1962). Nansen (1924--cited by Hjort and Ruud, 

 1938) reported taking shrimp (presumably 

 P. borealis ) by midwater fishing of bag nets 

 in Denmark Strait. 



We have been studying the life history, 

 behavior, and ecology of pandalid shrimp in 

 Kachemak Bay, Alaska, since 1963. We have 

 used pots and bottom trawls to collect the 



1 It Is uncertain whether the beach seines were fished 

 for pandalid or crangonid shrimp. 



shrimp. Incidental visual observations and 

 several sets with pots at midwater and near 

 the surface showed that many shrimp leave 

 the bottom, especially during the night. In 

 addition, we found that some species could be 

 captured in far greater quantities in pots 

 set off the bottom than on the bottom. Thus, 

 the studies reported in the literature and 

 our own limited observations showed a need 

 for a method to investigate the vertical dis- 

 tribution of shrimp. 



In this paper we describe a method of 

 pot fishing that was developed to study the 

 seasonal and diel vertical distributions of 

 pandalid shrimp. In addition, we point out the 

 value of this method in studies of popula- 

 tions of shrimp in untrawlable areas. 



EQUIPMENT AND FISHING METHODS 



The basic unit of gear was five pots spaced 

 at intervals from the bottom to the surface 

 along a vertically suspended line (fig. 1). An 

 anchor was attached to one end of the line, 

 and a surface buoy and a trailer buoy were 

 attached to the other. Heavy nylon twine loops 

 for attaching the pots were tied to the line 

 in the following positions: (1) 1 foot (0.3 m.) 

 above the bottom end, (2) one-quarter of 

 the distance from the bottom to the surface, 

 (3) one-half of the distance from the bottom 

 to the surface, (4) three-quarters of the 

 distance from the bottom to the surface, and 

 (5) 2 feet (0.6 m.) below the surface. A loop 

 for a subsurface buoy was tied 2 feet (0.6 m.) 

 above the three-quarter point between pots 4 

 and 5 (fig. 1). The length of line was equal 

 to the depth fished. 



The anchor was a round lead trolling weight 

 (25 to 50 lb. --11. 3 to 22.7 kg.) heavyenough to 



