Able and Grothues: Diversity of the estuarine movements of Morone saxatilis 



431 



Seasonal occurrence in the estuary 

 was the result of departure and re-entry 

 of individual fish (Fig. 2). The number of 

 departures for individuals ranged from 

 to 7, whereas arrivals ranged from to 

 6. In both years most departures and ar- 

 rivals occurred in the spring and during 

 the fall and early winter and not during 

 mid-winter or summer. In 2003, most 

 departures (n=27) from the estuary oc- 

 curred between weeks 12 and 21 (late 

 March-May) and again between weeks 

 39 and 48 (late September-mid Novem- 

 ber), whereas in 2004 departures (n=14) 

 occurred later, during weeks 17-23 (mid 

 May-mid June) and later (n=A) in weeks 

 27 and 45 (mid July and early November 

 (Fig. 2). In 2003, most arrivals (n=4) 

 were detected during weeks 40-46 (be- 

 ginning October and early November) 

 and earlier (n=2) during weeks 16-20 

 (mid May-beginning June), whereas in 

 2004 most arrivals in=l) occurred dur- 

 ing weeks 12-20 (mid March-beginning 

 June) and later (n = 17) during weeks 

 37-46 (mid September-mid November). 



The departure and arrival times 

 (Fig. 2) corresponded with the sea- 

 sonal increase and decrease, respec- 

 tively, of estuarine inlet temperatures 

 (Fig. 3). In both years the number of 

 departures (21% of total fish) and ar- 

 rivals (21%) was low at temperatures 

 <10°C and >20°C, respectively. During 

 the period between these temperatures 

 (when 79% of both departures and arriv- 

 als occurred), departures occurred at a 

 mean of 13.9°C and arrivals occurred at 

 a mean of 14.0°C. These temperatures 

 typically occurred during the spring and 

 fall (Fig. 3). 



Patterns of arrival and departure 

 were especially interesting for several 

 individuals that revisited the study 

 area during 2003 and 2004. The best 

 evidence for frequent, seasonal re-en- 

 try and departure from the study estu- 

 ary comes from the redetection of six 

 striped bass tagged on 2 April 2003 

 at Graveling Point (Fig. 4). Of these, 

 four returned and departed on several 

 occasions. For three of these individu- 

 als (tags 95, 97, 99) the pattern of the 

 timing of return and departure was nearly the same 

 over several seasons (winter 2003, spring and winter 

 2004). Another individual (with tag 96) was rede- 

 tected only once, but it reappeared (spring 2004) at 

 the same time as the other individuals. Even those 

 fish that were not redetected during a later season or 

 year typically departed the estuary at the same ap- 



Tag no. 95 



Retum/Depart 



8/1/03 



12/1/03 



4/1/04 



Tag no. 96 



• Depart 



I 



8/1/04 



Return/Depart 



8/1/03 



12/1/03 



4/1/04 



8/1/04 



Tag no. 97 



Depart 



Return/Depart 



V 



-**- 



:1 



4/1/03 

 30 

 25 

 20 

 15 

 10 



5 







4/1/03 

 30 



25 



20 



15 



10 



5 





 4/1/03 



8/1/03 



12/1/03 



4/1/04 



8/1/04 



Tag no. 99 



Return/Depart 



Deparl 



Depati 



8/1/03 



12/1/03 



4/1/04 



8/1/04 



R 



Tag no. 1 05 



Depail 



8/1/03 



12/1/03 



4/1/04 



8/1/04 



Figure 4 



Occurrence and distribution of selected individual striped bass (Morone 

 saxatilis) tagged on 2 April 2003 at Graveling Point. Filled circles indi- 

 cate when there were detections by hydrophones. Distance upstream 

 is from Little Egg Inlet gate (hydrophones 1-4, 13, reported as km 

 from the inlet) to Chestnut Neck gate (hydrophones 6-8, 18 km from 

 the inlet). Lower Bank gate (hydrophone 10, 28 km from the inlet), and 

 Sweetwater gate (hydrophone 12, 38 km from the inlet). 



proximate time (spring 2003 and spring 2004) as the 

 other fish (Fig. 2). The close agreement in seasonal 

 arrival to and departure from the estuary is probably 

 the result of seasonal migrations during which fish 

 enter this estuary, and probably other estuaries, on 

 their migration south in the winter and north in the 

 spring. 



