aestivalis ), alewife (A^. pseudohar engus ), 

 and American eel ( Anguilla rostrata ). 



Seasonal fluctuations inthe number of species 

 in the foregoing groups are shown in figure 3. 

 The sharp decrease in number of species from 

 October to February corresponds to a period 

 of rapid cooling. In February, when coldest 

 water temperatures occurred, only resident 

 species were taken in sannples. Warfel and 

 Merriman (1944) described a similar relation 

 between temperature and numbers of species 

 from Morris Cove, Conn.; however, they caught 

 no fish in winter in waters below 4°C, 



TOTAL - 



Figure 3. — Seasonal distribution in numbers of 

 species in White Creek, Del. 



M J 

 fish 



Two peaks in availability of fish in White 

 Creek were indicated from the seasonal dis- 

 tribution of catches per unit haul (figure 4). 

 An early peak in May consisted principally of 

 Atlantic menhaden. The second peak, in 

 November, was composed almost completely 

 of four resident species (Atlantic and tidewater 

 silver sides, mummichog, and sheepshead min- 

 now). Lowest level of availability occurred in 

 February, coincident with minimum water 

 temperatures. The dominance of Atlantic men- 

 haden among spring-fall migrants is obvious 

 when the abundance of Atlantic menhaden shown 

 in the upper part of figure 4 is compared with 

 abundance of all spring-fall migrants shown in 

 the lower portion. 



The change in length of seines employed 

 should be considered in interpreting figure 4, 

 The 7.5-m. seine was used from April to 

 September, and the 30-m. seine from late fall 

 to early spring. Thus, the September peak of 

 Atlantic menhaden probably results from im- 

 proved net efficiency rather than from in- 



creased abundance. Also, some increase in 

 availability may have occurred as the fish 

 grouped into larger schools prior to emigration. 



AMJJASONOJFMAMJ 

 Ip5l2el ».l 68l52 I I II I I I I l40l .p l 7;i„ 



I ,2 I I I 12 I I 86 I 63 I 30 I 30 I 32 I 8 I 24 [ 44 I a I 82 I 30m 

 NUMBER OF HAULS SEINE 



400 



300- 



200- 



3 

 < 

 I 



100 



< 



A M 

 1957 



S 



N D J F M A M 

 1958 



Figure 4. — Seasonal abundance of fishes in White Creek, 

 Del., indicated from the average monthly seine catches. 



DISTRffiUTION OF PRINCIPAL SPECIES 



Seasonal variation in the relative abundance 

 of the principal species occurring in the fore- 

 going arbitrary groups is shown in figure 5 



