WALTERS: ECOLOGY OF HAWAIIAN SERGESTID SHRIMPS 



Cruise 



Table l.-Summary of sampling, 1970-73. 



Dates 



Samples 



Remarks 



3-m IKMT' horizontal open tows 



3-m M'P horizontal opening-closing tows 



3-m IKMT shallow and deep oblique open tows 



3-m MT horizontal and oblique open tows 

 3-m IKMT stratified oblique open tows 



||KMT = Isaacs-Kidd midwater trawl. 

 2MT = modified Tucker trawl. 



Oblique Series: 

 Teuthis XVIII and XXII 



Teuthis XVIII, 30 September to 4 October 1972, 

 represented a departure from our normal sam- 

 pling program. It consisted of a series of oblique 

 tows vi^ith a 3-m Isaacs-Kidd midwater trawl 

 (IKMT) designed to assess the relative importance 

 in numbers and biomass of the various groups of 

 micronekton, and also to determine the proportion 

 of the mid-water community undergoing diurnal 

 vertical migration (Table 1). Two series of oblique 

 tows were taken: "deep" tows from the surface to 

 1,200 m, and "shallow" tows from the surface to 

 400 m. The catches were preserved unsorted in 5% 

 Formalin seawater and returned to the laboratory, 

 where they were sorted into the major taxa, 

 blotted dry, counted, and weighed. Further details 

 of sampling methods and results can be found in 

 Maynard et al. (1975). The sergestids were divided 

 into half-red and all-red types, counted, and 

 weighed. They were later separated by species, 

 counted, and sexed, and the carapace length 

 measured. 



Teuthis XXII, 23-27 May 1973, followed the 

 same sampling protocol as Teuthis XVIII, with 

 series of shallow and deep oblique tows. Sergestids 

 from this cruise were separated by species, count- 

 ed, and sexed, and the carapace length measured. 



Eflfects of Moon: 70-12 and Echo IV 

 The Teuthis cruises were unevenly spaced in 



time, making it difficult to use the data for study- 

 ing growth rates and other aspects of population 

 dynamics. In particular there were no cruises at all 

 between early November and late January. To fill 

 this gap in the seasonal coverage, I examined the 

 sergestids from the December 1970 cruise of T. A. 

 Clarke (70-12). This cruise used a 3-m IKMT for an 

 extensive series of 2- and 3-h horizontal open tows 

 in the upper 1,250 m of the water column (Table 1). 

 Further details of sampling can be found in T. A. 

 Cla'rke (1973). While the material from this cruise 

 helped balance the seasonal data, it raised new 

 questions about the vertical distribution of ser- 

 gestids. Many of the species in the 70-12 samples 

 showed abnormal vertical distributions. Since the 

 cruise took place near full moon, it appeared that 

 the abnormalities, in particular the absence of 

 normal vertical migration patterns in some 

 species until the final two nights of the cruise, 

 were related to lunar phase. Unfortunately, shal- 

 low and deep tows were not taken on the same 

 night, so it was unclear whether entire populations 

 were affected and on which night normal behavior 

 resumed. 



The sampling program of Echo IV attempted to 

 clarify these problems. We planned to make shal- 

 low and deep oblique tows with a 3-m IKMT from 

 first quarter to full moon in an attempt to find 

 when vertical migration ceased. Mechanical 

 difficulties postponed the cruise until three nights 

 before full moon; migration had already ceased by 

 this time. The sampling protocol called for a 

 shallow tow, either 0-200 m or 200-400 m; an 



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