behave like live ones, but they do provide some 

 information on flow characteristics through the 

 net and how easily objects are pinned against the 

 mesh. 



The results of the release of preserved salmon 

 smolts into the mouth of the pelagic trawl on two 

 cruises in the open ocean are shown in Table 2. 

 Ninety-seven percent of the fish released in the 

 mouth were recovered in cod end nets 1 and 2 

 within 5-25 min after release: 827c were recovered 

 in net 1. These data indicate an average residence 

 timeofpreservedfishof <10min in the body of the 

 trawl. 



If live animals were delayed by 10-120 min in 

 passing through the net into the cod end, then the 

 number of animals found in different cod end nets 

 may vary, with largest numbers in latter nets and 

 fewest in the first or second net as found by Foxton 

 (1970) and Donaldson (1975) in other cod end 

 opening-closing devices. Coefficients of concor- 

 dance, W, (Tate and Clelland 1957) were not sig- 

 nificant (P>0.2) for rank order of abundance of 

 fishes (12 tows), squids (10 tows), and Steno- 

 brachius leucopsarus, the most common fish (10 

 tows) for nets 2-5 that sampled equal time inter- 

 vals and also caught at least 10 of each of these 

 three types of animals. Similar nonparametric 

 tests of the rank order of abundance of 15 common 

 species were not significant for nets 2-5 of nine 

 tows with same net, where each net fished 2 h 

 (Willis 1979). This lack of correlation of catch with 

 net number provides no evidence for delay or stag- 

 nation of animals in the net over time periods of 10 

 min to 6 h. Characteristic species compositions or 

 size-frequency distributions from specific depths 

 (Willis and Pearcy^) also indicate that cod end 

 catches are predominantly from the depths fished. 



Entanglement or hang-up of fishes and 

 cephalopods in the meshes of the trawl appeared to 

 be restricted to a few types. Fishes such as the 

 stomiatoid, Tactostoma macropus, were oc- 

 casionally found hanging on the meshes of the 

 trawl body by their teeth. Soft-bodied cephalopods, 

 such as Chiroteuthis calyx and Vampyroteuthis in- 

 fernalis, were sometimes entangled in the mesh. 

 The number of animals hung on the net after a tow 

 was always a small fraction of those in the cod 

 ends. These entangled animals that are retained 

 in the net from one tow are probably washed-down 



Table 2. — Results of release of preserved salmon from the ejec- 

 tion device in front of the pelagic trawl. All tows were horizontal 

 at 2.5-3.0 kn. ND means no data. 



'Net failed to close 



2Cod end of trawl was twisted. This trawl was excluded from percentage 

 calculations. 



into the first net of the next trawl. Since this first 

 net is the one that fishes obliquely from the sur- 

 face to the selected depth of sampling, it is not 

 usually used in studying vertical distribution of 

 animals. 



Pelagic Trawi-IKMT Comparisons 



The 17 pelagic trawls caught almost twice as 

 many species of fishes, and about the same number 

 of cephalopod species as the 16 IKMT's during the 

 two major cruises in 1976 and 1977. These differ- 

 ences are mainly due to the large volumes of water 

 filtered by the pelagic trawl and consequently the 

 large number of individuals captured. 



One of the most significant differences between 

 the catches was the presence of some fish species in 

 the pelagic trawl and their complete absence in 

 the IKMT catches (number caught-vessel, where 

 PR = Pacific Raider and EX = Excalibur): 

 Aphanophus carbo (3-PR), Merluccius productus 

 (3-PR), Idiacanthus antrostomus (23-PR), Aristo- 

 stomias scintillans (24-PR, 6-EX), Macrouridae 

 id-PR), Lestidium ringens (37 -EX), Nansenia Can- 

 dida (22-EX), Symbolophorus californiensis (5- 

 EX). In over 2,000 (2, 2.5, and 3 m mouth opening) 

 IKMT tows made off Oregon since 1961, we have 

 never before captured Aphanophus carbo or M. 

 productus in oceanic waters. These fishes were 

 large (436-570 mm) and presumably always avoid 

 IKMT's. 



Length- Frequency Comparisons 



^Willis, J. M., and W. G. Pearcy. Spatial and temporal varia- 

 tion in the population size structure of three lanternfishes (Myc- 

 tophidae) off Oregon. Unpubl. manuscr. 



532 



Significant differences [P<0.5, Kolmogorov- 

 Smirov (K-S) two sample comparisons (Tate and 

 Clelland 1957)] were found in the size-frequency 



