448 



Fishery Bulletin 88(3). 1990 



o 



o 



o 



§§ i 



• Pooled 



a 1977 



a 1978 



O 1979 



V 1980 



O 1981 



« AbserH 



Figure 9 



Catch/effort (mean numher/ 

 10-min tow) by depth for 

 Piilydartylut; octonemux off 

 Freeport, Texas, each year 

 and pooled, October 1977- 

 August 1981. Tows in Janu- 

 ary and February were 

 excluded in calculating ef- 

 fort because no fish were 

 captured then. 



fish had already begun to move offshore as noted be- 

 low. Abundance was generally high at 9-16 m, although 

 it often declined with increasing depth in this range. 

 Abundance declined sharply between 18 and 22 m. 



Young-of-the-year P. octonemus in the northwestern 

 Gulf recruit to estuaries and coastal waters <5-16 m 

 deep. Many young recruited to Galveston Bay in April 

 and May when 50-110 mm (Fig. 10). In the Gulf, re- 

 cruitment was greatest at the shallowest depths oc- 

 cupied. Fish 50-120 mm and 2-4 months old mainly 

 recruited to 5-9 m in March-May, although some 

 recruited as deep as 16 m (Fig. 11 A, Table 2). Fish were 

 most abundant at 5 m. Their abundance declined with 

 increasing depth and was very low deeper than 13-16 

 m. Only one recruit was taken deeper than 16 m, the 

 75-mm fish at 86 m in April that may have been in a 

 pelagic stage. 



Polydactylus octonemus gradually disperse to deeper 

 water in early summer and thereafter. Few age-0 fish 

 were captured deeper than 9-13 m in April and May, 

 but they were found at 18-27 m in June and were abun- 

 dant at 16 m in July (Table 2). This gradual offshore 

 dispersal is supported by the size gradient that existed 

 seaward from Galveston Bay in June-December (Table 

 3), i.e., the smallest mean sizes were usually in Gal- 

 veston Bay and the shallowest Gulf depths. 



Larger P. octonemus lead the offshore dispersal. 

 Minimum sizes were similar at each depth in the Gulf 

 and in Galveston Bay during May (Fig. 10, 11 A). In con- 

 trast, size compositions showed gradients of increas- 

 ing size with depth in June, July, August, September, 

 and October, suggesting larger, presumably older, fish 

 move offshore first (Fig. 11A,B,C; Table 3). 



Peak abundance of P. octonemus shifts towards 

 deeper waters as they disperse offshore. Abundance 

 was greatest by far at 5-9 m in May and June, then 

 included 13 and 16 m in July as fish dispersed offshore 

 (Table 2). Abundance peaked at 16 m in August and 

 September, although fish were abundant from 5 or 9 

 to 18 m, and at 16-24 m in October (Table 2). 



Polydactylus octonemus abandon estuaries and in- 

 shore portions of the Gulf (<5-9 m) in late fall and 

 occupy only the offshore portions (13-24 m) before 

 disappearing in November and December. Two fish at 

 9 m in November were the only individuals captured 

 shallower than 13 m in the Gulf in November and 

 December (Table 2), although peak abundance was at 

 5-9 m in May and June. Gallaway and Strawn's (1974) 

 data show a similar abandonment of estuaries by late 

 fall (Fig. 10). 



Polydactylus octonemus were most abundant in 

 July-September and least abundant November-April 



