area appears to be S. disdorsalis (Hendrickx 

 1984). Although several species of Sicyonia from 

 the Pacific coast of America have a wide distribu- 

 tion range, S. penicillata seems to be restricted to 

 the southern half of Baja California and the cen- 

 tral and northern Gulf of California (Hendrickx 

 1984). 



Abundance 



A total of 3,502 specimens were collected during 

 the sampling operations, including 1,919 females 

 (55%) and 1,583 males (457c ). Generally S. penicil- 

 lata was rare or uncommon at most of the trawl 

 stations. Most of the catches were < 1 kg/h and 

 commercial-size catches were obtained only twice 

 during the survey (33 and 66 kg/h). The largest 

 catches of all were from the northernmost part of 

 the Gulf at stations 38 and 39 (Table 1) and rep- 

 resented 97 and 88% of the crustacean catch and 6 

 and 69% of the total catch, respectively. All of the 

 sampling was done during daytime or at dusk. 

 Nighttime captures might prove to be much 

 higher as has been the case with S. brevirostris on 

 the Florida's West Central Shelf (Huff and Cobb 

 1979). 



TABLE 1. — Sampling conditions and abundance (kg/h of trawl- 

 ing) of Sicyonia penicillata in the Gulf of California during the 

 survey (catch = for the rest of the stations). 



Bathymetric Range and Substrate 



The species seems to occupy a wide bathymetric 

 range. It has been reported by Burkenroad (1938) 

 from the beach level (under stone) down to a depth 

 of 72 m. In the present study, the shrimp were 

 collected at depths between 26 and 100 m (Table 1). 

 Information on bottom substrates was obtained 

 from samples collected during the same cruise and 



processed by the Laboratorio de Geologia Marina 

 of the Marine Station of Mazatlan and have been 

 summarized in Table 1. Maximum abundance was 

 found at stations with smooth bottom made of 

 compact mud and of very fine sand, although 

 specimens were also collected in small numbers on 

 bottoms made of coarse sand and of crushed shell- 

 sand. 



The distribution pattern of the species in the 

 Gulf indicates a preference for the shelf of the 

 northern Gulf and the eastern central Gulf. No 

 specimens were found at station 19 and south- 

 ward, along the Baja California coast, where sand 

 and gravel were observed. The absence of S. 

 penicillata from the southeastern Gulf platform, 

 where substrate varies with depth from fine sand 

 to mud (mostly silty mud mixed with clay), is 

 probably due to other factors such as water tem- 

 perature or dissolved oxygen level which can be 

 lower than 1 ml/1 at bottom level in this area 

 (January and April data) (Hendrickx et al. 1984), 

 or to competition with S. disdorsalis. 



Natural Diet 



As in other penaeid shrimp, food in the stomach 

 of Sicyonia is usually finely triturated, making 

 difficult identification of the components of the 

 diet (Cobb et al. 1973). Relative importance of var- 

 ious food items in the diet is listed in Table 2 (20 

 stomachs). 



All stomachs examined were at least 30% full 

 and 12 of them were at least 50% full. Sampling 

 was done in late afternoon, and the degree of 

 stomach fullness indicates that the species feeds 

 during daytime. Crustaceans were the most fre- 

 quent item in the diet, followed by small mollusks 

 and polychaetes. Unidentifiable organic matter 

 was present in almost every stomach (80% ) and, in 



TABLE 2. — Food items in the diet of Sicyonia 

 penicillata (20 stomachs). 



Food items 



% Frequency of 

 occurrence 



Algae 



Forammifera 



Nematoda 



Polychaete fragments 



Mollusca; Gastropoda 

 Fragments 



Crustacea: Copepoda 

 Isopoda 

 Amphipoda 

 Fragments 



Fish scales 



Pellets 



Unidentifiable organic matter 



Sand, silt. etc. 



15 

 15 

 10 

 40 

 20 

 40 

 5 

 10 

 35 

 70 

 30 

 45 

 80 

 20 



717 



