HASTINGS: BIOLOGY OF PYGMY SEA BASS 



ing conditions, but whether they require such 

 changes is unknown. For species such as S. 

 pumilio, which are territorial, competition by 

 other species with similar habitat requirements 

 may be important. Two potential competitors of 

 S. pumilio are noted in the following section. 



HABITAT 



Serraniculus pumilio apparently occurs typi- 

 cally at moderate depths (10-70 m) over the con- 

 tinental shelf but may occasionally occur in shal- 

 low coastal waters less than 1 m deep. It has 

 been recorded as deep as 117 m (Bullis and 

 Thompson, 1965). 



During this study, the species was often com- 

 mon in the shallow waters along the jetties at 

 East Pass of Choctawhatchee Bay in depths of 

 about 1-10 m but was usually absent during Jan- 

 uary and February. Inshore populations of Ser- 

 raniculus apparently move offshore to deeper 

 water during the winter. The lowest temper- 

 atures at which the species was recorded at East 

 Pass were 13°-14°C. Shallowwater tempera- 

 tures in the northern Gulf often drop below 10 °C 

 during the winter, while the temperature in 

 water deeper than about 18 m usually remains 

 above about 15°C. The minimum temperature 

 extreme at which S. pumilio can survive may be 

 about 13°C. 



Like other small serranids, this species is most 

 common over sand or shell bottoms near irreg- 

 ularities such as coral or rock outcrops. Springer 

 and Woodburn (1960) noted that it was similar 

 in this respect to Centropristis ocyurus, another 

 species restricted to the continental shelf. Ser- 

 ranvs tigrinus and S. baldwini (Robins and 

 Starck, 1961) also occupy such habitats at about 

 the same depth range as Serraniculus pumilio, 

 but these two species are restricted primarily 

 to coral reef areas of the West Indies where 

 Serraniculus is not found. 



A few specimens of Serraniculus have been 

 collected in grass beds (mostly Thalassia and 

 Syringodium) at the mouth of Alligator Harbor. 

 However, in such areas, numerous bare patches 

 of sand bottom are present, and there are accu- 

 mulations of shell debris in places which provide 

 suitable habitat for the species. 



Apparently Serraniculus pumilio does not have 

 a particularly restricted home range. The num- 

 ber of individuals observed on the East Pass 

 jetties varied considerably, indicating that in- 

 dividuals were often moving into and out of 

 the area. These observations were based upon 

 adults or advanced juveniles; hence recruitment 

 of populations on the jetties resulted from move- 

 ment of adults, not from the immigration of re- 

 cently spawned young. The pattern of move- 

 ment of adults is not known, but more stable 

 populations may occur on the numerous lime- 

 stone reefs which lie short distances offshore 

 in the area. Accumulations of mollusk shells 

 occur over most of the sandy bottom in the area 

 and small fishes suoh as Se7'raniculus could use 

 such accumulations for shelter when moving over 

 open bottoms. In this way Serraniculus could 

 easily move the few miles from the offshore reefs 

 to the jetties. 



BEHAVIOR 



Springer and Woodburn (1960) described 

 Serraniculus pumilio as sedentary, but individu- 

 als apparently move about considerably. The 

 fish rests on the bottom using its pelvic fins as 

 props and moves about in short "hops" over 

 the bottom. It appears to be territorial and 

 protects its temporary abode (near a large shell, 

 rock, or coral ledge) from intrusion by other 

 fishes. The size of the area defended is not 

 known, but when two or more individuals were 

 placed in a 20-gal aquarium, one became dom- 

 inant and forced the other fish to remain off 

 the bottom, even when several rock piles were 

 provided as hiding places. 



During agonistic displays, Serraniciilus 

 spreads its dorsal and caudal fins and gill covers, 

 and presents the lateral side of the body to the 

 opponent (Figure 1). During these displays, 

 the dark and light bands on the side of the body 

 become more distinct and series of small, pale 

 spots are clearly visible along the rays of the 

 dorsal and caudal fins. These displays are fol- 

 lowed by the fish beating the side of its opponent 

 with its caudal fin and the posterior part of its 

 body. When one individual proves subordinate, 

 it retreats with its dorsal fin depressed and usu- 



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