ABSTRACT 



Sonically measuring distances between points in 

 an otter trawl during operation by use of trans- 

 ducers and an echograph recorder presents prob- 

 lems. For example, when the headrope height of 

 an otter trawl is about one-half the wing-end spread, 

 the head-rope and wing-end measurement traces ap- 

 pear at the same location upon the recording paper. 

 The simultaneous overlay of signals can be corrected 

 by use of a sonic echo reflector to replace one of 

 the wing-positioned transducers in the measuring 

 system and by use of the echo-signal method instead 

 of the direct-signal method. The echo signals, how- 

 ever, are weaker than the direct signals. 



This paper reports on a test of three reflectors: 

 plain wood, aluminum sheet, checkered aluminum. 

 All three reflectors gave usably strong echo signals. 

 The best quality signal was given, however, by the 

 aluminum reflector. 



Vol. 4, No. 4. Effect of gamma radiation on 

 thiaminase activity in freshwater fish. By 

 Richard A. Krzeczkowski. July 1968, pp. 133- 

 138, 2 figs., 5 tables. 



ABSTRACT 

 Sensitivity to gamma radiation of the antime- 

 tabolite thiaminase in whole fish was studied so that 

 the potential usefulness of this radiation for con- 

 trolling the activity of thiaminase in fishery products 

 could be estimated. Although gamma radiation will 

 partially inactivate thiaminase in the species stud- 

 ied, its use for complete inactivation does not appear 

 to be economically feasible. 



Vol. 4, No. 4. Relation of temperature, time, 

 and moisture to the production of aflatoxin in 

 fish meal. By Travis D. Love. July 1968, 

 pp. 139-142. 



ABSTRACT 

 Numerous instances have been reported in which 

 moldly vegetable meals, when incorporated into 

 feeds, have produced sjTnptoms of acute toxicity in 

 animals. The several toxin principles (aflatoxins) 

 produced by the mold Aspergillus flai^us have been 

 isolated in crystalline form and chemically identified 

 as lactones, epoxides, or hydroperoxides. 



Commercial fish meal has never been reported to 

 contain aflatoxins. In this study fish meal was 

 heavily inoculated with Aspergillvs flaviis, and the 

 concentration of moisture was artificially increased 

 to 18 percent. The meal developed aflatoxins after 

 being held at 28°C for 35 days. The control meals, 

 which had a normal moisture concentration of 10 

 percent, did not produce aflatoxins at any temper- 

 ature studied, though they were heavily inoculated 

 with Aspergillus flavus and held for 35 days. 



Vol. 4, No. 4. Variation in the fatty acid com- 

 position of Pacific herring (Clupea harengiis 

 pallasi) oil in Alaska during 1964 and 1965. 



By Paul A. Robisch and Edward H. Gruger, 

 Jr. July 1968, pp. 143-150, 9 tables. 

 ABSTRACT 

 Industrial users need knowledge about the vari- 

 ability in the fatty acid composition of Alaska her- 

 ring oil. Accordingly, oil from the 1964 and 1965 

 catch seasons was analyzed for certain of its chem- 

 ical properties — individual fatty acid composition, 

 total concentration of the saturated, monoenoic, and 

 polyenoic fatty acids, iodine value, saponification 

 value, free fatty acid value, and peroxide value. 



The individual fatty acid components varied to 

 some extent. Ranges in the concentration of the 

 monoenoic fatty acids for the 2 years did not over- 

 lap; the average differed by 4.8 percent. Differen- 

 ces in the averages for the saturated and polyenoic 

 fatty acids were only 1.7 percent. Data on iodine 

 value indicated that the total unsaturation of the 

 oil was somewhat greater in 1964 than in 1965 ; data 

 on the other chemical properties indicated that the 

 oil had not undergone appreciable alteration prior 

 to being analyzed. 



The reasons for the above variations could not be 

 determined, since several variables were operating 

 simultaneously. 



Vol. 4, No. 4. Author index of publications and 

 addresses — 1966. Bureau of Commercial 

 Fisheries Branch of Technology and Branch 

 of Reports (Seattle). By Helen E. Plastino 

 and Mary S. Fukuyama. July 1968, pp. 151- 

 164. 



(No abstract.) 



Vol. 4, No. 5. Shrimp-behavior studies underly- 

 ing the development of the electric shrimp- 

 trawl system. By Edward F. Klima. Decem- 

 ber 1968, pp. 165-181, 16 figs., 9 tables. 

 ABSTRACT 



Observation of how shrimp react to different 

 amounts of electrical energy and repetition rates 

 of pulsating direct current in the laboratory and 

 the field provided information on the electric char- 

 acteristics needed for an effective electric shrimp 

 trawl. 



The laboratory studies showed the electric thresh- 

 old voltage of shrimp oriented at different positions 

 to the electrodes and the effect of different voltages 

 on the shrimp's responses. Threshold voltages were 

 affected by the animal's position relative to the elec- 

 tric field, and the shrimp's reaction increased with 

 an increase in voltage. 



The field studies provided information on the elec- 

 trical output needed to force burrowed shrimp out 

 of the substrate. Capacitor-discharge pulses of 4 

 per second with a potential of 3.0 volts or more 

 across 100 millimeters parallel to the electric field 

 were best for forcing shrimp out of the types of 

 bottom on some of the commercial shrimping 

 grounds in the Eastern Gulf of Mexico. 



