Louisiana State University, Baton Rouge). Apparently 

 shallow natural channels fill with sediments because 

 man-made canals capture waterflow. This phenomenon 

 also occurs where highway embankments cross tidal 

 marshes and disrupt natural channels, which subse- 

 quently fill in. The reduction in the edge: area ratio 

 under these circumstances suggest that the quality of 

 the natural environment has been reduced. Docu- 

 mentation is poor, but in at least one case it has been 

 shown that marsh macrophyte production was signif- 

 icantly reduced (Allen 1975) when edge: area ratios 

 were reduced. 



Refuges. An important component of the natural 

 resource productivity of a basin is its capacity to serve 

 as a refuge for animals. The term "reftige" impUes a 

 variety of uses for a habitat in addition to use primar- 

 ily for its food (trophic) value. "Refuge" also includes 

 shelter provided by habitats which may lie outside of- 

 ficially designated private. State, or Federal refuge 

 boundaries. For threatened and endangered species 

 and perhaps others, the value of the gene pool may 

 far outweigh other values. A habitat, e.g., ridges, rhay 

 provide refuge for migrating species at a critical time, 

 which gives it a value far in excess of its normal carry- 

 ing capacity. 



Species that require refuges can include animals 

 that migrate daily over short distances (intrabasin) as 

 well as seasonal, long-range migrants. Intrabasin 

 migrants include roseate spoonbills and bald eagles, as 

 well as reptiles and mammals that spend part of their 

 lives on ridges and feed in wetlands. Seasonal long- 

 range migrants include a wide range of organisms such 

 as warblers, waterfowl, juvenile shrimp, and even 

 monarch butterflies. 



Natural marshes (salt, brackish, intermediate and 

 fresh) are being lost in the Chenier Plain at the rate of 

 about 1%/yr (table 3.56). Other less abundant habi- 

 tats are often destroyed by man because they are par- 

 ticulariy desirable for development. Wooded cheniers 

 are scarce in the low-lying areas of the Chenier Plain 

 and are particularly suitable for building sites. 



The location and size of private. State, and Federal 

 refuges within the Chenier Plain are identified in plates 

 6A and 6B and table 3.34. These refuges represent 

 14% of the inland area of the Chenier Plain and are 

 comprised of wetland and aquatic habitats whose pri- 

 mary use is for wateri'owl, alligator, and fur manage- 

 ment. The fact that they are closely supervised, that 

 hunting is controlled, and that development is re- 

 stricted make them excellent refuges for threatened 

 and endangered species. For instance several pairs of 

 red wolf are beheved to reside on the Sabine National 

 Wildlife Refuge. On the other hand most of the re- 

 fuge land within the Chenier Plain has been impounded 

 so that movement of migratory fishes and shellfishes 

 between impounded areas and estuaries is discouraged. 

 These refuges therefore represent tradeoffs between 

 fish species and game species. 



Forested cheniers and swamps are two habitats 

 that are rapidly being exploited and should be con- 

 sidered "critical" in the sense of their vulnerability to 

 complete eradication in the region. The latter are 



abundant elsewhere along the Louisiana coast, but 

 local areas of undisturbed swamp within each basin 

 cover less than 1% of the area and are being lost at a 

 rate of about 0.25%/yr (table 3.5 5). Forested cheniers 

 are perhaps the major unique feature of the Chenier 

 Plain. These ridges have been extensively developed, 

 and are in danger of being irretrievably lost. 



Bird rookeries and archeological sites (plates 6A 

 and 6B) are other unique features on the Chenier Plain 

 landscape that fall under tlie general category of re- 

 fuges. 



Commercial and Sport Species. Harvest of the 

 most commercially important species in the Chenier 

 Plain— menhaden, shrimp, oyster, blue crab, nutria, 

 and muskrat— was discussed in part 3.2.4. Long-term 

 harvest trends for these species suggest that they are 

 being exploited at their maximum, and with the pre- 

 sent carrying capacity the possibility of significantly 

 increased harvests is remote. 



Menhaden. Menliaden harvest has increased reg- 

 ularly since 1946 (fig. 3-26). The effort expended 

 during the 1969 to 1974 period seems to be resulting 

 in the maximum sustainable yield (Schaafet al. 1975). 

 Similar clupeid fisheries on the East and West coasts 

 have suffered dramatically from over exploitation. 



Shrimp. Although year-to-year catch fluctuations 

 are fairly large, the white and brown shrimp harvest 

 (1959 to 1973) shows no consistent upward or down- 

 ward trend (figs. 3-27 and 3-28). It is possible that en- 

 Ughtened management can result in some increase, but 

 this would be through control of the size of harvested 

 shrimp, not through increased production potential. 

 Continued wetland loss will eventually be reflected in 

 harvest reduction. 



Oyster. Oyster production varies a great deal lo- 

 cally, since oyster growth depends on suitable sub- 

 strate, favorable salinities, and flowing waters. The 

 trend in the Chenier Plain has been to a reduction in 

 size or loss of oyster beds, or at least to closure be- 

 cause of pollution. This has occurred in the Calcasieu 

 and Sabine basins and in part of East Bay Basin. Oyster 

 production can be increased by appropriate manage- 

 ment as is shown by the development of oyster beds 

 where spoil banks have washed out along the Calcasieu 

 Ship Channel (Van Sickle 1977). However, unless pol- 

 lutant discharge is controlled, oyster production will 

 undoubtedly continue to decline. 



Blue Crab. The small size of the blue crab industry 

 suggests that exploitation could be expanded in the 

 Chenier Plain. Blue crabs are scavengers that seem to 

 adapt to conditions associated with man's develop- 

 ments. For instance, the blue crab industry in Sabine 

 Lake is thriving despite the decline of other species. 

 It would be surprising if the environmental degrada- 

 tion did not adversely affect the edibUity of crabmeat. 

 Even if fully exploited the value of this fishery would 

 be small compared to shrimp and menhaden. 



Other Fishery Species. The only Other group of 

 fish for which an unexploited potential seems to exist 

 is the industrial bottomfishes. The industrial bottom- 



83 



