SHANKS: SHOREWARD LARVAL TRANSPORT 



1985b). The behavior of the megalopae (Sulkin and 

 Van Heukelem 1981) and their distribution in the 

 plankton (Smyth 1980; Johnson 1985a) both suggest 

 that these larvae are inhabitants of the neuston. Lar- 

 vae that inhabit the neuston can be transported on- 

 shore by internal waves (Shanks 1985). On 4 and 24 

 June and 21 August the densities of Callinectes spp. 

 megalopae and first crabs were significantly higher 

 in the convergence zones over the internal waves 

 than in the divergences, suggesting that Callinectes 

 spp. were being transported onshore by the sampled 

 internal waves. On 24 June, when Callinectes spp. 

 were uncommon, there was not a significant differ- 

 ence in the density of Callinectes spp. in front vs. 

 behind the internal wave nor was there a significant 

 difference in the density of blue crabs over vs. in 

 front of the set of waves. These results are mixed, 

 but they do suggest that the megalopae of Calli- 

 nectes spp. may be transported shoreward in the con- 

 vergence zones over internal waves. 



The megalopae of a variety of crab species were 

 only caught in the water column (Table 3 and see 

 Johnson 1985a). Some of these megalopae as adults 

 occupy near shore and even estuarine habitats. If 

 these megalopae migrate onshore they must be 

 utilizing some mechanism of onshore transport other 

 than slicks over internal waves. 



In conclusion, the data presented in this paper in- 

 dicate that in an area where the tides are of small 

 amplitude and the continental shelf is wide, inter- 

 nal waves are nevertheless capable of transporting 

 larval invertebrates and fish shoreward. The sam- 

 ples collected on 24 June 1985 more critically test 

 the hypothesis that internal waves cause cross-shelf 

 transport and the results support the hypothesis. 



ACKNOWLEDGMENTS 



Assistance with the field work was enthusiastical- 

 ly provided by 0. McMillan, G. Safrit, J. Purifoy, 

 and W. Graham. G. Safrit, in addition, heroically and 

 with really very little complaint, sorted most of the 

 plankton samples. Comments by M. Kingsford and 

 R. Forward improved the manuscript. Figures were 

 prepared by V. and H. Page and F. Schwartz helped 

 to identify larval fish. 



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