28° 



116° 



26° 



114° 



24° 



112° -* 



22° 



110° 

 20° 



108° 



-j. 



FIGURE 1. — Location of the sampling stations (solid cir- 

 cles) and distribution of Sicyonia penicillata (striped 

 area) according to the occurrence of this species in the 

 samples. 



spring balances. Whenever members of one 

 species or genus accounted for a large part of the 

 total catch, they were weighed apart from the rest 

 of the catch. 



Samples were immediately fixed with a 8% sea- 

 water solution of Formalin 2 , except for the 



Sicyonia samples that were stored in the deep 

 freezer of the vessel at a temperature of -25°C. 

 Frozen samples of S. penicillata were later used in 

 the laboratory to determine individual weights 

 ( W) with a top pan electric balance (± 0.05 g preci- 

 sion). Total length (TL: rostrum tip to telson tip) 

 and carapace length (CL: orbital margin to mid- 

 posterodorsal margin of carapace) of the shrimps 

 were obtained with a dial caliper to the nearest 0.1 

 mm. Determination of linear and exponential re- 

 lationships, TL-CL and W-CL, followed the 

 method of Sokal and Rohlf (1969). 



The analysis of the foregut contents was done 

 with a series of 20 specimens that were selected at 

 random from among the material obtained during 

 trawling activities. The foreguts were removed by 

 dissection, their contents analyzed under magnifi- 

 cation, and the frequency of occurrence of each 

 food item was calculated and expressed as a per- 

 centage of the total number of foreguts examined. 



Results and Discussion 



Geographic Distribution 



Sicyonia penicillata was first described by Lock- 

 ington (1879) from Bahia Bolinas (sic), Baja 

 California (?Bahia Ballenas) and Bahia de Los 

 Angeles in the Gulf of California. Brusca (1980) 

 reported the species as the most common rock 

 shrimp from the Gulf of California (Gulf) and from 

 the west coast of Baja California where it was 

 found as far north as the Laguna Ojo de Liebre 

 (lat. 27°45' N). It also occurs in bays of the western 

 side of the Gulf (Burkenroad 1934, 1938). 



During the present study, S. penicillata was 

 found in the northern part and along the east coast 

 of the Gulf, south to Punta Arboleda (lat. 

 26°45'N), and was captured at 13 of the 32 sam- 

 pling stations (Fig. 1). Although a wide continen- 

 tal shelf runs uninterruptedly from this latter lo- 

 cality south to Bahia Banderas, at the southern tip 

 of the Gulf, the species seems to be absent from the 

 southeastern part of the Gulf. Indeed, monthly 

 sampling made in Bahia de Mazatlan over a 2-yr 

 period and intensive trawling operations made on 

 the continental shelf of southern Sinaloa (lat. 

 22°14' to 23°37'N) on three occasions during a 

 period of 1 yr did not bring up a single specimen of 

 S. penicillata, and the dominant species for this 



2 Reference to trade names does not imply endorsement by the 

 National Marine Fisheries, Service, NOAA. 



716 



