in Texas waters. The reefs stood about 2 feet alDove the surface of the surrounding mud. 

 The najority of oysters on the "bar wore in vertical position, v;hich is usiially asaumed "by 

 the oyster in order to protect itself from Tjeing engulfed in mud. 



A few years ago, the oyster Ijars in Knsenada Garachin^ were extensively fished 

 ■fay the local residents. There was no organized trade., Oysters v;ere used primarily for 

 consTimotion at home, but occasionally some of them were ship-oed to Panama. It was said that 

 the reefs v;ere prolific for the last ten years, but that the majority of oysters died in 

 19U7. Examination of the reef confirmed this information. Most of the oysters were dead, 

 although the valves were still connected by their hinges. During one hour of intensive 

 search, I was able to find only seven adult live oysters and 13 live seed. The seed oysters 

 varied from 1 to 2 l/2 Inches in length (2.S-6.6 cm.). Examination of the tissues showed 

 no -oathologicELl conditions. Only one specimen v/as lightly infested with Henatopsis spores. 

 The cysts vj-ere found only in the adductor muscle. Of 10 oysters v/hich v/ere examined 

 microscopically, one small specimen (l inch long, 2,S en.) was in an indifferent sex stage. 

 Others contained either ripe sperm or eggsi there were foiir males and five females. Many 

 of the shells of dead oysters, especially the small ones, were drilled by snails which 

 abounded on the reef. It v/as obvious, hov;ever, that mass mortality of oysters was due to 

 some other cause than depredation by borers. Long exposure at low tide, which may have 

 been caused by an unfavorable combination of v/ind and tides, may have killed these oysters. 

 The -oresence of snail seed oysters indicated that setting on the bar continued. It Is 

 therefore reasonable to expect that, in a fev; years, the oyster population of the bar will 

 be re-established. 



Since oyster reefs in Ensenada Garachin^ ere valuable to the local population as 

 a source of protein food, it is desirable that they be managed in such a vay as to prevent 

 their destruction. Because of the small number of live oysters remaining on the bar at 

 present, it is suggested that the bar be temporarily closed, and that fishing resumed v/hen 

 the oyster poprulatlon is re-established. 



PROBABLE CAUSE OF THE DEPLETION Or PEARL-OYSTER ffiOXnTOS 



From the observations made in the field, and from the examination of the pre- 

 served tissue of pearl oysters, the follov;ing facts become evident. The remaining 

 population of pearl oysters on the principal grounds known to have been productive in the 

 past years is so small that it cannot support the fishery. For practical purposes, the 

 pearl fishery in Panama has ceased to exist. 



The surviving pearl oysters appear to be healthy. They develop gonads» and, 

 judging by the presence of small numbers of young oysters, the propagation of the species 

 continues, although at a very low rate. In the absence of precise information regarding 

 the rate of growth, it is difficult to foresee v/hen the population of pearl oysters may 

 reach its former abundance. My guess is that, barring unforeseen circumstances, the 

 rehabilitation of the grounds would require a decade or more, provided the fishing is com- 

 pletely discontinued, and oysters are permitted to propagate and grow without any Inter- 

 ference from man. 



Field observations do not disclose any evidence that pearl oysters were killed by 

 the red tide or by the dumping of some poison. I observed no significant difference in the 

 conditions of sea bottom around Pearl Islands, Colba, or along the mainland of the v/estem 

 part of the Gulf of Chiriqul. If the assumption is correct that oysters vrere killed by 

 poisons bro^oght in by the currents from the dumping area in the deep water at the entrance 

 of the Gulf of Panama, one v/ould expect higher mortality rate around Pearl Islands than at 

 Colba, located more than'200 miles east of the dumping area, and separated from the Gulf of 

 Penama by a large penins\ila (Fig. 6) . 



The resistance of various marine organisms to adverse conditions is different. 

 Some of them are hardier than others, and therefore may survive in the concentration of 

 poison lethal to less resistant forms. It is, hov^ever, inconceivable that any poison may 

 be so selective as to kill only one species without affecting others living in the same 

 environment. The Panama pearl oyster does not form densely populated reefs or banks 



U6 



