74 Fred C. Rohde and Rudolf G. Arndt 



Aphredoderus sayanus (10), Acantharchus pomotis (1), Enneacanthus 

 gloriosus (3), Lepomis gibbosus (5), Lepomis macrochirus (6), and 

 Etheostoma olmstedi (26). 



Cottus bairdi habitat in Caroline and Dorchester counties, Mary- 

 land, including physicochemical characteristics, is as described for Butler 

 Mill Branch. Maryland fish species-associates include some of those 

 listed previously, plus Etheostoma fusiforme and Percaflavescens. 



RESULTS AND DISCUSSION 



Reproduction 



Spawning occurs in February and March. Two females taken 17 

 March 1974 each contained only two ova, indicating the end of spawning. 

 On 2 March 1975, 1 of 3 1 females was spent and, although other females 

 contained ova, there were fewer than in 1974, 1979, and 1980 pre- 

 spawning samples, indicating spawning was under way. Spawning was 

 completed by 23 March; all ovaries were empty except for some ova 

 being resorbed. Spawning in 1979 was later, and females collected on 16 

 March still possessed a full ova complement. In 1980 females spawned 

 primarily between 9 and 22 March: on 9 March none had spawned, on 15 

 March 2 of 22 were spent, by 22 March all but 1 were spent, and on 30 

 March all taken were spent. Examination of specimens in the field in 

 1981 yielded the following ratios of females heavy with eggs to spent 

 females: 22 February, 13:1; 27 February, 10:2; and 7 March, 7:3. On 

 subsequent dates all taken had completed spawning. 



February and March spawning is generally earlier than that reported 

 for C. bairdi. Other reports based on direct (deposited eggs) or indirect 

 (mature ova or specimens in breeding condition) evidence are: Nagel 

 (1980), Tennessee, early April; Ludwig and Norden (1969), Wisconsin, 1 

 April to 3 May; Ricker (1934), Ontario, middle of May; Bailey (1952), 

 Montana, most of June; Gage (1878), New York, April; Koster (1936), 

 New York, April to June; Smith (1922), Michigan, April and May; Rob- 

 ins (1954), Appalachian region, late March to early May. Pflieger (1975) 

 found presumed C. bairdi eggs in Ozark streams from early November to 

 late February. William L. Pflieger (pers. comm.) has confirmed records 

 of eyed eggs from 2 February 1971 and of males guarding egg masses with 

 embryos far enough advanced to show movement on 23 and 29 February 

 1971, which indicates spawning occurred at least as early as January. This 

 early spawning, however, may not be attributable to C. bairdi, as most 

 Ozark populations are considered to represent an undescribed species. 



Ovary weight as a measure of gonad development during 1973-75 

 was low in October and November 1973, increased rapidly in January, 

 and peaked in February 1974 (Fig. 2, Table 1). The gonosomatic ratio 



