Literature Cited 



Cox. B A . AND R G Mauerman, 



1976. Incidental catch and disposition by the Brownsville- 

 Port Isabel Gulf shrimp fleet. Cameron Co. Ext. Ser., 

 San Benito, TX. and Texas Shrimp Assoc, Brownsville 

 TX, 55 p. 

 Fritts.T H . a B Irvine. R D Jennings, L A Collum. W Hoff- 

 man. AND M A McGehee. 



1983. Turtles, birds and mammals in the northern Gulf of 

 Mexico and nearby Atlantic waters. U.S. Fish Wildl. 

 Serv. Div. Biol. Ser., Wash., D.C., 455 p. 



HiLLESTAD, H O , J I Richardson, and G K Williamson. 



1978. Incidental capture of sea turtles by shrimp trawler- 

 men m Georgia. Proc. Ann. Conf Southeast. Assoc. 

 Fish Wildl. Agencies, p. 167-178. 



Hopkins, S., and J Richardson. 



1984. A recovery plan for marine turtles. U.S. Gov. 

 Print. Off., 281 p. 



Rabalais. S C, and N. N Rabalais. 



1980. The occurrence of sea turtles on the south Texas 

 coast. Contrib. Mar. Sci. 23:123-129. 

 Snedecor. G W . AND W G Cochran. 



1967. Stastical methods. [6th ed.] Iowa State Univ. 

 Press, Ames, lA, p. 536-537. 



Tyrrell A Henwood 

 Warren E Stuntz 



National Marine Fisheries Service, NOAA 

 Southeast Fisheries Center 

 Mississippi Laboratories 

 Pascagoula Facility 

 Pascagoula, MS 39568-1207 



THE RELATIONSHIP BETWEEN LUNAR 

 PHASE AND GULF BUTTERFISH, 

 PEPRILUS BURT/, CATCH RATE 



Through the joint efforts of Japan and the United 

 States, a research program was conducted in fall 

 1984 and spring 1985 to identify squid resources 

 in the northern Gulf of Mexico (Grace 1984, 

 1985). Although large concentrations of squid 

 were not located, commercial quantities of gulf 

 butterfish, Peprilus burti, were encountered. 

 Maximum sustainable yield (MSY) estimates 

 from the spring data indicated annual potential 

 catches of 50,000 t with a projected ex-vessel 

 value of $19 million (GledhilP). Although gulf 

 butterfish are sufficiently abundant to support a 

 fishery, critical gaps of information on gulf but- 



iGledhill, C. T. 1985. A preliminary estimate of gulf but- 

 terfish [Peprilus burti) MSY and economic yield. Unpubl. 

 manuscr., 66 p. Southeast Fisheries Center, Mississippi Labo- 

 ratories, National Marine Fisheries Service, NOAA, 

 Pascagoula, MS 39568-1207. 



terfish distribution and location exist which are 

 needed in order to harvest this resource effi- 

 ciently. Preliminary data from the U.S. -Japan 

 joint surveys indicated that gulf butterfish catch 

 rates were greatest at bottom temperatures of 

 15°-19°C. Subsequent scientific and commercial 

 efforts at targeting gulf butterfish based upon 

 bottom temperature have produced catches rang- 

 ing from few individuals to many tons. In a recent 

 study, we found that fishing success for gulf but- 

 terfish was often high for several days followed by 

 periods of low success (Allen et al. 1986). This 

 phenomena parallels catch patterns encountered 

 by east coast gulf butterfish fishermen (Amos^), 

 who suggest that lunar phase affects catch rates. 

 We analyzed the effect of lunar phase on catch 

 rates. The purpose of this paper is to present evi- 

 dence that bottom trawling success for gulf but- 

 terfish is related to lunar phase. 



Methods 



Gulf butterfish catches from the two U.S.- 

 Japanese joint surveys and from an additional 

 gulf butterfish survey conducted by SEAMAP 

 (August 1985) were examined. Initially, catch 

 rates per hour of individual trawls were calcu- 

 lated per calendar day. A lunar day value (1-29) 

 was assigned to each calendar day of trawling 

 during the three cruises. Lunar day 1 was as- 

 signed to the third calendar day proceeding the 

 new moon on through day 29 falling on the third 

 calendar day following the last quarter moon 

 phase. Mean catch (kg/hour per lunar day) was 

 then calculated and plotted. Catches from trawled 

 stations outside of the depth range in which gulf 

 butterfish were caught during each trip (i.e., 

 < minimum depth or > maximum depth) were 

 not included when calculating mean catch/hour 

 per lunar day. 



The effects of moon phase and trip on natural 

 log catch rates (ln(a: + 1), where x = kg/hour per 

 individual trawl) of gulf butterfish were investi- 

 gated, using the general linear model (GLM) pro- 

 cedures (SAS) Institute (1982). Type III sums of 

 squares were used for the analysis due to unequal 

 number of observations in each subclass. Each 

 observation from each trip was assigned into a 

 lunar phase period (1-4). Mean catch (ln(x + 1)/ 

 hour) and number of trawls sampled during each 

 trip and lunar phase are presented in Table 1. An 



^Duncan Amos, Georgia Marine Extension Program, P.O. 

 Box Z, Brunswick, GA 31523, pers. commun. July 1986. 



FISHERY BULLETIN: VOL 85, NO 4. 1987. 



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