Conservation of Endemic Rain Forest Fishes of Sri Lanka: Results of a Translocation Experiment ERIC D. WIKRAMANAYAKE* Department of Wildlife and Fisheries Biology University of California, Davis Davis, California 95616, U.S.A.
Abstract: Four potentially endangered species of rain forest fishes, Barbus cumingi, Barbus nigrofasciatus, Barbus titteya, and Rasbora vateraoris, endemic to streams of southwestern Sri Lanka, were translocated in 1981 into a depauperate stream system in the central hills. By 1985 all four species had established self-perpetuating populations in these streams, and had extended their ranges into adjacent stream Barbus nigrofasciatus, a generalist, was one of the most abundant species in these stream It was widely dis- tributed throughout the stream system and in the slower sections of the Mabaveli Ganga (=Mabaveli River), and oc- cupied a wide range of macro- and microhabitat types. The other three species were more specialized in their habitat and diet, and were thus patchily distributed. The microhabitats occupied by B. cumingi, B. titteya, and R. vateritloris resem- bled the specialized microhabitats they occupy in their na- tive stream Presumably because of their specializations, these three species were not as abundant as B. nigrofasciatus. Overall, the biology and distribution of the four species will enable them to survive spatially small-scale environmental perturbations The results suggest that translocations are a feasible means of conserving other endemic fishes of Sri Lanka theatened with extinction. However, such transloca- tions must be carefully planne4 with consideration for the indigenous community as well as the ecological require- ments and genetic integrity of the target species.
Resumen Cuutro especies de peces, potencialmente en pe- ligro de extinci6n de zonas de selvapluvial, Barbus cumingi, Barbus nigrofasciatus, Barbus titteya y Rasbora vaterifloris, que son endemicas a 10s rios del sudoeste de Sri Lanka, f u m n reubicadas, en 1981, a un sistema empobrecido y deterio- rado de nos, en las colinas centrales de esepais. En 1985 las cuatro especies habian establecido poblaciones auto- petpetuuntes en estos nos, y habian expandido su rango a nos adyacentes. Barbus nigrofasciatus, un generalist4 era unu de las especies truiS abundantes en estos rios Esta espe- cie se distribuio extensamente por todo el sistema de n,os y en las secciones truiS lentas del Mabaveli Ganga (el do Ma- haveli), y ocupo un amplio rango de tipos de macro- y mi- cro-habitats. Las otras tres especies son mciS especializadas en su habitat y dieta, y, por ello, se distnbuymn en f o m a irregulat: Los microhabitats ocupadospor B. cumingi, B. tit- teya, y R. vateriiloris se parecian a 10s microhabitats espe- cializados que ocupaban en sus rios nutivos. Sepresume de quepor su especialiazacioq estas tres especies no eran tan abundantes como B. nigrofasciatus. En general, la biologia y distribucion de las cuatro especies posibilitara su sobre- vivencia a perturbaciones ambientales de pequetia escala en lo espaciai Los resultados sugieren que la reubicacion es unu forma viablepara conservar a otrospeces endh icm de Sri Lanka amenazados de extinci6n. Sin embargo, las reubi- caciones deben ser cuidadmarnente planificados tanto en consideracion a la comunidad autoctoria, como, a las necesidades ecologicos y la integridad genetica de las espe- cies en consideraci6n.
Present address: Department of Herpetology, me National Zoolog- ical Park, Smitbsonian Institution, Washington, D.C 20008 Paper submitted 9/14/88; revised manuscript accepted 2/13/89.
Conservation Biology Volume 4, No. 1, March 1990
Wikramanayake Consemtion of Endemic Elshes of Sri h k a 33
The rain forests of Sri Lanka are rapidly being depleted by agriculture, mining, logging, and urbanization. Be- tween 1956 and 1980, total forest cover had been re- duced from 44 percent to 25 percent (TAMS Report 1980). Loss of rain forest is resulting in rapid declines in species abundances, and many are threatened with ex- tinction. One manifestation of rain forest loss is stream habitat degradation due to increased erosion, siltation, extreme flow fluctuations, and decreased shade and cover. Such conditions are largely unsuitable for special- ized rain forest fishes, many of which are endemic to Sri Lanka (Evans 1981; Senanayake & Moyle 1982; Moyle & Senanayake 1984).
Following a survey of the freshwater fishes of Sri Lanka by Senanayake (1980), Evans ( 1981 ) concluded that of the 15 endemic species, 2 were rare (taxa with small world populations that are not at present endan- gered or vulnerable, but are at risk), 7 were vul- nerable ( m a believed likely to move into the endan- gered category in the near future if the causal factors continue operating), and 2 were endangered (taxa in danger of extinction, whose survival is unlikely if the causal factors continue operating) (Table 1 ). Presently, Labeo fish@ which only inhabits deep, fast-flowing sections of the mid to upper reaches of the Mahaveli Ganga (Ganga = River), may already be extinct as a result of habitat loss following the accelerated Mahaveli River Development Project (F. R. Senanayake, personal communication). Other fishes endemic to the south- western rain forest streams are now threatened with habitat loss if the proposed dammings of two major riv- ers in the wet zone, Kalu Ganga and Gin Ganga, are implemented. Because these two drainages hold most of the endemic fishes and because extinctions seem inev- itable following river development (Sheldon 1988), it is imperative that a comprehensive conservation pro-
Table 1. Endemic fishes of S r i Lanka and their status, as listed bv Evans 11981).
SDecies Status ~
Cyprinidae Barbus cumingi Vulnerable Barbus nigrofasciatus Vulnerable Barbus pleurotaenia Vulnerable Barbus titteya Vulnerable Rasbora vatmyoris Vulnerable Labeo fisben Endangered
Belontia signuta Rare Malpulutta kretseri Vulnerable
Cbanna orientalis Rare
Lepidocepbalus jonklassi Endangered
Sicydium balei Vulnerable
gram be initiated immediately. To conserve endemic fishes, Evans (1981) and Senanayake & Moyle ( 1982) proposed ( 1) captive breeding of commerical stocks, (2) regulation of fisheries, (3) better watershed man- agement, and (4) translocation of sensitive species to establish refuge populations.
In 1981, Senanayake & Moyle (unpublished data) translocated four species of fishes, Barbus curningi B. nigrofasciatus, B. titteya, and Rasbora vatmporis, en- demic to the lowland rain forest (wet zone) streams, into depauperate streams in the central mountains within the wet zone (Fig. 1 ). The translocations were an experimental effort to establish refuge populations of these vulnerable species. Here, I present the status of this experiment, investigated four years following the translocations, and comment on the feasibility of further translocations to conserve other endemic fishes of Sri Lanka.
Sri Lanka has centrally located hills surrounded by low- land, and presents a three-peneplain topographic profile (Fig. 1 ), with steep interpeneplain transition zones. Wet and dry zones are determined by differential rainfall
Rasbora vateritloris -~
Figure 1. Distribution of translocated species, Barbus cumingi, B. nigrofasciatus, B. titteya, and Rasbora va- terifloris, in streams of the upper Mahaveli Ganga (= Mahaveli River) drainage. The original transloca- tion sites are indicated by arrows The Mangles indi- cate waterfalls and the solid bar indicates a &m, both of which presumably act as barriers to the translocated fishes The relationship between Ceypo- tha Ela and the tributary network is described in the text. The inset shows the peneplain system and the wet and dry zones of Sri Lanka The location of the translocation streams is indicated by the star.
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34 Conservation of Endemic Fishes of Sri h k a
from the northeast and southwest monsoons (Costa 1980). Most major rivers originate in the central hills and radiate coastward. Over 30 co-occurring species can be found in the first peneplain wet-zone streams, but the second and third peneplain streams usually have S 1 2 and S 5 native fish species, respectively (Senana- yake 1980). Except for L. fisher4 all endemic fishes are native to the wet-zone drainages.
The fish were translocated into several small streams of the upper Mahaveli Ganga drainage (Fig. 1). The in- digenous fishes in these streams are also part of the species assemblages found in the streams to which the translocated species are native. Thus, the translocations were made into assemblages composed of fishes with which the translocated species co-occur in their native streams. The translocation streams were also selected for their similarity in physico-chemical characteristics to the native streams of the translocated species (F. R. Senanayake & P. B. Moyle, personal communication). Translocated fishes were wild-caught, either by Senana- yake and Moyle or by commercial collectors. Although the exact streams from which the fishes were collected are not known, the approximate locality and the river drainages for three species are known (Table 2). The propagule stocks ranged from 3&90 individuals each (Table 2), but the sex ratios and the proportions of juveniles to adults were not recorded.
Indigenous fish species in the translocation streams included herbivores and carnivores; therefore, any en- demic algae, macrophytes, and invertebrates were as- sumed not to be adversely affected by the transloca- tions. Furthermore, some streams had upstream barriers preventing the translocated fishes from colonizing en- tire stream lengths. Thus, any endemic invertebrate fauna and flora would have spatial refugia from exploi- tation by these fishes.
In 1985, I surveyed the translocation streams, adjacent streams, and the section of the Mahaveli Ganga to which
W b a n a p k e
these streams were confluent to evaluate the status of the translocation. To determine species distributions, surveys were made by walking along the streams and observing fishes from the surface; snorkel surveys were made when necessary. For the most part these streams are shallow with clear water, making surface observa- tions a practical means of obtaining data on the fishes' presence or absence.
I determined relative abundances of species by sein- ing twenty stations in each of two translocation streams, Horakoda Ela (ela = stream) and Ceypotha Ela. Twenty stations in Koladeniya Ela (Fig. l), a stream into which three species, B. cumingi, B. nigrofasciatus, and Rasbora vaterifloris, had expanded their ranges, were also seined. The stations were located in stream sections where I had previously documented microhabitat use by both translocated and indigenous fishes (Wikra- manayake 1988). Within these sections I sampled pri- marily in areas that were amenable to seining. The pro- cedure involved placing up- and downstream block nets three meters apart, then removing all large objects such as logs and boulders from within the enclosure to facil- itate seining. Care was taken to minimize disturbing the fish within the potential seine station while the nets were set up. Since activity in the stream tended to at- tract fish from downstream, the downstream net was always set up first. I then seined each station from bank to bank (across stream) with a 3 m seine. Each station was seined until no fish were captured. This enabled me to catch nearly all the fish within a section and also to standardize the effort. AU fishes collected were identi- fied to species, measured (standard length, mm), and released. Catches were recorded separately for each ef- fort ( = seine sweep).
At each station I measured stream width at 0, 1.5, and 3.0 m of the station length. I then determined mean water column velocity (at 60 percent depth; see Bovee & Milhous 1978) and depth at 0.25,0.5, and 0.75 of the distance along each of the above cross-transects using a Gurley pygmy current meter (Model 625) mounted on a topsetting wading rod. The area of each station was
Table 2. Numbers of fishes introduced (propogule stocks) into the streams (ela = stream) of the upper Mahaveli Ganga (=Mahaveli River) drainage. The drainage of the source population is also given, with the general l d i t y .
SDecies ~ ~~
Introduction Barbus Barbus Barbus Rasbora streams cummingi nigrofasciatus titteya vaterifloris
- Balantota Ela - 60 31" Ceypotha Ela - 30 22 52 Ceypotha Ela tribs. - - Horakoda Ela - Kahawatura Ela 50 60 - 56 Walapita Ela - 87 91a 28" Origin of Source Population (drainage locality)
- 31 - - 31
Kelani Ganga; Kalu Ganga; unknown Kelani Ganga, Dehiowita Kalutara Parakaduwa
a Indicates unsuccessful translocations
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Conservation of Endemic Fishes 01 Sri Lanka 35
then determined as the product of the average width (mean of cross-transect widths) and station length ( = 3 m). All values for water velocity and depths at each station were averaged to obtain mean velocity and depth for each station (data presented in Wikramana- yake 1988). Relative abundances and species densities (fish 10 m-) in each stream were also calculated. Spe- cies densities were calculated by considering only those stations where the respective species occurred.
Results Of the 13 translocations of four species into six streams, 10 successfully established self-perpetuating popula- tions (Table 2). The translocations that did not become established were B. titteya in Balantota Ela and Walapita Ela and R vatenporis in Walapita Ela. Three species, B. cumingi, B. nigrofasciatus, and R uateriforis, ex- panded their ranges into adjacent streams (Fig. 1). All three were, for example, found in Koladeniya Ela, a stream located between Kahawatura Ela and Walapita Ela, but on the opposite side of the Mahaveli Ganga. Both R uatenporis and B. cumingi had limited and patchy spatial distributions within each stream. Rasbora vatert$!oris was more abundant in Ceypotha Ela than in Koladeniya Ela, which was a more speciose stream (Ta- ble 3).
Barbus nigmfmciatus, however, was widely distrib- uted and utilized a wide range of habitats. In the three streams where it was found, B. nigrofmciatus was abun- dant in all stations sampled (Table 3). This species was found throughout most of the stream sections accessible to it, and in the slower sections of the river.
Barbus titteya was present only in Ceypotha Ela and its tributaries (Fig. 1, Table 3), which consisted of a network of small (50-75 cm wide, 20-40 cm deep) ditchlike streams that drained a small grass-shrub valley. Barbus titteya had extended its range from the original translocation site to include most of the tributaries. I could not sample this network extensively because ac- cess was difficult due to heavy vegetation and an abun- dant population of terrestrial leeches (Haemadipsa sp.). However, presence of B. titteya some distance from the introduction site suggests that the fish are now wide- spread throughout the network.
Discussion Habitat and Trophic Relationships All four species are maintaining self-perpetuating popu- lations in the translocation streams. Three species, B. cumingi B. nigmfmciatus, and R vatenifloris; have ex- tended their ranges beyond the original translocation areas. Barbus nigrofaciatus, a habitat and dietary gen- eralist (Wikramanayake & Moyle, in press), is the most successful species; it is found in virtually every stream and is one of the most abundant fishes. It occupies all
Table 3. Relative abundance (RA), total number collected (N), number of stations where species were found (Sl), and density (number of ash per 10 mZ) for species in Cerpotba Ela, Horakoda Ela, and Koladeniya Ela sampling stations.
Species RA N STN Density Ceypotha Ela (total area sampled = 343 m)
Barbus nigrofasciatus .64 640 20 Gawa lampta .23 230 17 Rasbora vatenifloris .07 65 7 Barbus titteya .03 32 9 Noemacbeilus notostigma .02 23 12 Opbiocepbalus gaucba ,004 4 3
Danio mulabarkus .48 504 20 Barbus nigrofasciatus .24 250 20 Rasbora daniconius .18 183 16 Barbus bimaculatus .04 46 9 Lepidocepbalus tbermalis .02 24 9 Belontia signata .02 15 6 Tor kudree longispinis .02 17 8 Cbanna orientalis .004 4 4
Horakoda Ela (total area sampled = 260 m)
Koladeniya Ela (total area sampled = 240 m) Barbus nigrofmciatus .57 357 20 Danio malabaricus .16 100 17 Rasbora daniconius .10 60 13 Tor kudree longispinis .07 45 19 Barbus cumingi .04 26 8 Belontia signata .03 17 8 Cbanna orientalis .o 1 4 4 Barbus bimuculatus .01 5 1
Noemacbeilus notostigma 1 1 Lepidocepbalus tbermalis .01 5 4
18.3 7.6 5.4 2.6 1 .o 0.7
21.2 9.3 8.3 3.3 2.0 1.9 1.5 0.7
13.7 5.6 3.7 2.0 2.3 1.8 1.0 3.8 1 .o
types of macrohabitats, such as pools, runs, and even riffles. Within these macrohabitats it utilizes a wide range of microhabitat types (Wikramanayake & Moyle, in press).
The three other species, B. cumingi, B. titteya, and R vatenpork, are more specialized, and occupied macro- and microhabitats similar to those they occupy in their native streams (Wikramanayake & Moyle, in press). Their respective diets (Wikramanayake & Moyle, in press) were also similar to the diets within their native range (De Silva & Kortmulder 1977; De Silva et al. 1977; Moyle & Senanayake 1984). These specialized habitat and microhabitat requirements and food habits may ex- plain their limited distributions and smaller populations. Since B. nigrofasciatus has more generalized habits and ecological requirements, it may be able to establish and maintain large populations by utilizing underexploited habitat types and food resources in these streams, which are less speciose than their native range streams.
Conservation Biology: Status of the Transldons and Recommendations for Future Translocations When establishing refuge populations it is desirable to maximize genetic representation of the target species and to maintain genetic integrity through time. The propagule stocks should then be large enough to (1) maximize intraspecific genetic variability in the refuge population or populations, and (2) maintain the genetic
Conservation Biology Volume 4, No. 1, Mar& 1990
36 Conservation of Endemic Fishes of Sri Lanka
integrity of the species through time by enabling refuge populations to survive demographic and environmental stochasticity and interspecific interactions such as com- petition and predation (see comprehensive treatments in Soule & Wilcox 1980; ShalTer 1981; Frankel & Soule 1981; Schonewald-Cox et al. 1983; SoulC 1986, 1987; Meffe 1986). Appropriate founder sizes would necessar- ily depend on the biological, ecological, and genetic characteristics of the species (Soule & Simberloff 1986; Meffe 1987).
Most propagule stocks in these fish translocations were of around 50 individuals, but some populations were established with smaller stocks. For instance, only 30 B. nigrofmciatus were introduced into Ceypotha Ela, and these fish were effectively isolated from other B. nigrofmciatus populations by a series of high (>20 m) waterfalls. Nevertheless, the Ceypotha Ela population is established and flourishing. However, Ceypotha Ela had only three indigenous species, of which only one, Garra lamptq was abundant, compared to the ten indigenous species found in the other streams. Thus, B. nigrofm- ciatus in Ceypotha Ela may have survived in an envi- ronment of relative competitive release, compared to Kahawatura Ela, Horakoda Ela, and Walapita Ela. Al- though the stock populations in Kahawatura Ela (n = 60) and Walapita Ela (n = 87) were greater, the stock population in Horakoda Ela (n = 3 1 ) was similar to the stock population in Ceypotha Ela. Barbus nigrofmcia- tus was established in Horakoda Ela, but it is not known whether this population was derived from the original propagule stock or if the stream was secondarily in- vaded by B. nigrofmciatus that had become established in other streams. Any future translocations should be monitored closely and continually soon after they are made so that these initial dynamics of population biol- ogy and ecology can be followed.
Despite relatively extreme and stochastic environ- mental variations in the form of high flows during heavy rainfall, when water levels can increase by more than a magnitude of the mean depth (personal observation), all four species have established self-perpetuating popula- tions. This is probably attributable to the existence of spatial and temporal refuges, in which the fish were protected due to their life histories, or both. The large population and the wide distribution should ensure that B. nigrofmciatus will survive stochastic environmental variability in these streams unless the variabilities are of a catastrophic scale that affects the entire system. Fur- thermore, being serial spawners, they reproduce throughout the year, and the probability of extinction through the effects of environmental variability on de- mographic stochasticity is low.
Barbus cumingi and R vateraifloris occur in isolated patches in different streams. Thus, although they could conceivably be eliminated by spatially large-scale envi- ronmental catastrophies, the populations can survive lo- calized perturbations, even if intense, since range exten-
sions by both species suggest that they have the potential to recolonize streams. Barbus titteya is the only species that is highly localized and restricted in its distribution. However, the population in the small trib- utaries is not subject to the high flow regimes that fishes experience in the larger streams following heavy rain. The limited access to these streams also provides refuge from anthropogenic stresses. Thus, the refuge popula- tions should continue to survive through environmental variations and demographic perturbations, provided that the spatial and temporal scales of extreme pertur- bations do not include the entire stream system.
The results of this translocation experiment suggest that a more comprehensive program aimed at conserv- ing other endemic fish species of concern (Table 1) is feasible. However, a number of considerations must be taken into account prior to implementing such a proj- ect. Among these are:
1. Determine the ecological requirements of the po- tential translocation species and of the species compris- ing the recipient assemblages. I suggest that detailed analyses of macro- and microhabitat utilizations and trophic relationships be made using methods detailed in Wikramanayake ( 1988). These data will help determine whether the translocation species will fit into the re- cipient assemblage without intense interspecific inter- actions that may lead to extinctions in either group of species. Furthermore, the macro- and microhabitat availability and food availability in the introduction streams should be determined to ensure that suitable habitat and food are available for the translocation spe- cies. This is especially essential for species that are hab- itat specialists. As an example, in this experiment, the B. titteya introductions into Balantota Ela and Walapita Ela were probably unsuccessful because of lack of suitable habitat. The chemical characteristics of the transloca- tion streams must also be similar to those of the native range streams.
2. Survey the invertebrate fauna and determine the dietary requirements of both indigenous fishes and the potential translocation species. If any endemic inverte- brate species (and algal species) are present, the trans- locations must be planned such that the invertebrates have spatial refugia from excessive fish predation.
3. The genetic and phenetic variability of the source populations should be determined to ensure that the propagule stocks are representative of the species to be conserved (Conant 1988). Such information also provides a means by which managers can monitor, and if desirable, maintain the genetic integrity of the refuge populations through time. However, management does not imply perpetuating photocopies (Carson 1983).
4. The propagule stocks should be large enough to ensure that maximal intraspecific genetic variability is incorporated into the refuge population (Soule &
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W h a n a p k e Consemtion of Endemic Fishes of Sri Lanka 37
Wilcox 1980; Frankel & Soul6 1981; Schonewald-Cox et al. 1983; Soule 1986, 1987; Meffe l986), and the sex ratio of the stocks should be determined, if possible. With endemic fishes, if speciation was due to genetic drift or genetic bottlenecks, there could be less genetic variability; thus, sampling error of refuge populations would be relatively less. However, less genetic variabil- ity among endemics derived from genetic drift or bot- tlenecks has to be determined.
5. Care should be taken to ensure that no diseases or parasites are introduced into the recipient communities during the translocations. All fishes to be translocated should be held in quarantine for a suitable period before being introduced.
Overall, this study shows that successful species trans- locations can be carried out to establish refuge popula- tions of species deemed threatened. However, they should be implemented judiciously. It is also important that future translocations be closely monitored from their inception.
Acknowledgments I thank Peter Moyle, Thomas Schoener, Mary Power, and fellow FERCers Larry Brown, Bill Bennett, Gina Sato, and Liz Strange for their reviews and valuable comments on various drafts of this manuscript. Gary Meffe and an anonymous reviewer also provided excellent reviews. Peter Moyle and Rani1 Senanayake kindly permitted me to use unpublished data on the initial translocations. I acknowledge the support, both moral and financial, given by Peter Moyle during this research. Dale Marcel- lini also provided logistical support during preparation of this manuscript. The study was partially funded by a Jastro-Shields Research Grant from the University of Cal- ifornia, Davis.
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Conservation Biology Volume 4, No. 1, March 1990
Special Section: Population viability Analysis
The following Comment and the three Contributed Papers that follow it constitute a special section of this issue of Conservation Biology on the subject of population viability analysis. The contributed papers are based on talks given at a symposium that was part of the annual meeting of the Society for Conservation Biology at Davis, California, in August, 1988. Dr. Mark Shafer, of the Cooperative Research Units Center of the U.S. Fish and Wild- life Service, was chair of the symposium.
Conservation Biology Volume 4, No. 1, March 1990