UCCTIS OH ECOLOGY OF SEASHOEE Aim SHAU.OW WAIiJl 



Pearl-oyster sro-'jnds in Panajna suita'Dle for conr,:ercial exploitation are confined 

 to a narrov; coastal zone stirrounding the islands. In '.7idth, this zone extends fror. lov;- 

 v.'ater mark to a depth of a'oout 12 fathons. P.ugged cliffs of volcanic origin, povnded Ijy 

 powerful siirf 1 are the most typical haoitat of the tidal zone, which in places extends 

 for about 29 feet vertically above mean low water. Because of this great raiige of tldep, 

 large shore areas, sonetiries several hundred feet v.'ide, are exposed at lov: v/ater. De-oend- 

 ing on the configuration of rocks, the slope is steep or .Viay be gentle (Pigs. S and S) • 

 Tropical jungle descends alnost the v/ater line, and the extended branches of the trees 

 frequently touch the surface of the sea at high tide. At everal stations, such tjA5ical 

 r.arine fon.is as barnacles and oysters vrere grov/ing on the lov/er sides of the horisontal 

 branches of the trees; v/hile concon land snails, Ortlialicus prince-ps d eceptor (Pilrbry) , 

 occupied the upxiersiost side of the same branch. On Isla de Mina, vrhere the photograph 

 (Pig. 9) was taken, several live snails v:ere collected fror: the branches of a nangrove 

 tree shovm in the center of the pict^Ji'e, v/hile naii;.' dead shells of this ST?ecies found on 

 groTind v;ere occupied by hernit crabs. The nonotonj' of roclqy shoreline is often inter- 

 rupted by a glistening exprjise of v/hite saiidy beaches wedged betv/een the bla,ckness of the 

 rocks (Pig. lO). Sone of the beaches are verj' small, not nore than a few hundred feet loiigt 

 v;hile others extend over a distance of several miles. 



A belt of muddy bottom, several miles •.^;ide, extends along the north and northeast 

 coast of the Gulf of Panama and on both sides of the Bay of San Miguel. Bottom deposits 

 of this area consist of a material washed out by soil erosion and deposited by fresh-v/ater 

 streams along the coast line. I had an opportunity to visit the mud flats in the Snsenada 

 de Garachinl, in the Bay of San Miguel, v;here they extend over an area about 12 miles long 

 and 7 miles Wide. A considerable portion of these flats is occu-oied by narrov: and long 

 reefs made of shells of the edible oyster, Ostrea chilensis Philippi. The reefs are bare 

 at lov; tide and are surrounded v;ith very soft and stick;;- riud. In general configuration and 

 structui-e, they resemble the oyster reefs of Ostrea virginica formed on muddy "oottonis in 

 Texas and Georgia (Galtsoff, 1931). 



Figure S Volcanic rocks along the nort?iern shore of 



Coiba Island - lov; tide. 



21 



