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I Dams, diadromous migratory fish and shrimp in

neotropical rivers and the fallacy of mitigation: the case of the La Amistad World Heritage Site (Costa

Rica-Panama)

Asoc. ANAI: Apdo. 170-2070 Sabanilla de Montes de Oca,

Costa Rica mmafla@anaicr.org

(506) 2756-8120

Río Yorkin

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DAMS, DIADROMOUS MIGRATORY FISH AND SHRIMP IN NEOTROPICAL RIVERS AND THE FALLACY OF

MITIGATION: THE CASE OF THE LA AMISTAD WORLD HERITAGE SITE (COSTA RICA-PANAMA)

Dr. WILLIAM O. McLARNEY Program Director

LIC. DANIELLE BOUCHONET Consultant

LIC. ANA MARIA ARIAS MORENO Research Coordinator

LIC. MARIBEL MAFLA HERRERA Program Codirector

Photo: HUGO SANCHÉZ Y MARCIO BONILLA (Naso Parataxonomists)

March, 2012

Asoc. ANAI: Apdo. 170-2070 Sabanilla de Montes de Oca, Costa Rica

mmafla@anaicr.org (506) 2756-8120

Web: www.anaicr.org

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TABLE OF CONTENTS

1. INTRODUCTION

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2. AN EXPERIENCE FROM COSTA RICA

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3. TEMPERATE ZONE FISH PASSAGE STRUCTURES FOR DIADROMOUS SALMONIDS

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4. SPECIAL CONSIDERATIONS IN TROPICAL RIVERS

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5. SHRIMP PASSAGE FACILITIES IN GUADELOUPE

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6. HISTORY OF FISH PASSAGE FACILITIES IN BRAZIL

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7. CONCLUSION

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REFERENCES CITED

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DAMS, DIADROMOUS MIGRATORY FISH AND SHRIMP IN NEOTROPICAL RIVERS AND THE FALLACY OF MITIGATION: THE CASE OF THE LA AMISTAD

WORLD HERITAGE SITE (COSTA RICA-PANAMA) 1. INTRODUCTION

The purpose of this paper is to briefly assess the probability of success in mitigating the barrier effect of large dams in the watersheds draining the huge binational (Costa Rica-Panama) protected area referred to as Reservas de la Cordillera de Talamanca/La Amistad, and especially its largest component, the La Amistad International Peace Park (PILA). However, we believe that our conclusions are broadly applicable to many if not all of the hundreds of dams proposed for the Mesoamerican region. The theoretical basis for our approach rests on the River Continuum Concept (Vannote et al., 1980), which recognizes that: “Large rivers are relatively continuous habitats for fishes, other biota, and ecosystem processes.” (Helfman, 2007)

In our 2010 report to the UNESCO World Heritage Committee (McLarney et al. 2010) we predicted that, no matter what attempts at mitigation are made, damming these watersheds as proposed will result in the elimination of a unique assemblage of 7-9 species of migratory diadromous1 fish plus a large but as yet poorly defined suite of shrimps. This prediction is justified on the basis of experience in other parts of the world, especially Puerto Rico, where the diadromous fish and shrimp fauna is very similar to that of Talamanca and Bocas del Toro, and where the extirpation of migratory fish above all dams is well documented (Kwak et al. 2007), as is the near-total extirpation of shrimp (Holmquist et al., 1998; Benstead et al., 1999, March et al., 2003, Greathouse et al. 2006a, 2006b). Mitigation for dam effects in the context of the La Amistad region is likely impossible, given the lack of detailed life history studies for any of the species in question and of workable fish passage models which might be adapted. Our view is supported by a study commissioned by the World Bank. Ledec and Quintero (2003) stated that “Fish passage facilities are usually of limited effectiveness for various reasons -including the difficulty of ensuring safe downstream passage for many adults and fry.” Here we wish to update and reinforce the case for the impracticability of fish passage facilities as mitigation, citing examples from North America, the Caribbean island of Guadeloupe, and Brazil. This report will focus on the concept of diadromy and attempts at mitigation for diadromous fauna. However, we should also recognize the threat posed by “disrupting the structure and function of metapopulations and compromising the long-term resiliency” of non-diadromous fishes (Liss et al. 2006), in and out of the World Heritage Site. That such 1 Diadromy” refers to a pattern of reproductive behavior shared by many fish and invertebrate species (“diadromes”). Diadromy has 3 recognized forms; the common element is the necessity for diadromes to travel between fresh and salt water in order to complete their reproductive cycle. Anadromous species (most famously the Pacific salmons) grow and mature in the sea but return to rivers to spawn. Catadromous species (notably the commercially important Anguillid eels) spend their adult lives in fresh water but return to the sea to spawn. Amphidromous animals (the majority of tropical species) lay their eggs in fresh water rivers, which carry the eggs and newly hatched larvae to marine environments where they partially complete development, typically returning to the rivers as juveniles.

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fragmentation can result in extirpation and even extinction of native fish species has been well documented for the Rio Grande watershed of Mexico and the southwestern United States (Williams et al. 1985) and has almost certainly occurred elsewhere.

While no endemic primary fresh water fish species have been identified from within the La Amistad World Heritage site Roman-Valencia (2000, 2002) has identified a new species of the widely distributed characid genus Bryconamericus (B. gonzalesoi) -from the lower reaches of the Changuinola-Teribe and Sixaola-Telire watersheds in both countries, including from the Rio Bon, site of the Bonyic dam. Roman-Valencia (personal communication) believes that the possibility of finding additional endemic species of Bryconamericus at higher elevations in these watersheds in high.

Two other genera of primary freshwater fishes found within the World Heritage site (Rivulus and Rhamdia) are considered to be taxonomically difficult, and have never been studied in the La Amistad area. In Costa Rica, Rivulus occurs over a broad range of elevations and is highly diverse on the Pacific slope, with at least 4 species recognized (Bussing, 1998). Presently only one species (R. isthmensis) is recognized from the Atlantic slope but Bussing (personal communication) postulates that there is a considerable possibility of regional endemism. The most recent species list for Panama (Froese and Pauly, 2012) shows 13 species, with 2 possibly endemic to the Bocas del Toro province.

2. AN EXPERIENCE FROM COSTA RICA The only citation we have found which suggests any possible success in mitigating dam effects on Neotropical migratory species is from another World Heritage Site, located on a small island in Costa Rica. Rojas (2005) cites the apparently successful passage of a suite of diadromous animals, including 5 species of fish (2 of them also found in the La Amistad watersheds, with the others represented by closely related species) and an unidentified Macrobrachium shrimp, through a fish passage structure located in the center of an ICE dam on the Rio Genio, in Isla del Coco National Park.

All 6 species, comprising all of the known diadromous fauna of Isla del Coco, were observed to successfully navigate this structure in an upstream direction. Over the period of study (2002-2005) the total number of diadromous animals observed upstream of the dam (fish plus shrimp) increased by 30%. While there is no documentation of successful downstream passage by any life stage of any species, the limited data cited do not suggest extirpations. In an earlier report Rojas (no date) rather disingenuously made reference to this effort as “evidence that planning and execution of this type of work permits the development of infrastructure in harmony with the surrounding ecology”. In fact, the crest of the dam on the Rio Genio is at the normal water surface level and might well be passable by some or all of the species without a special passage facility.

Subsequently Rojas (2005) modified his conclusion to state that “the inclusion of ecological passageways in mini-projects is a satisfactory method for minimizing ecological

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alterations in a critical stream reach.” This may be the case for a dam with an effective height of zero, but extrapolation from results at one such “mini-project” to the “large” dams planned (and in the case of CHAN-75 on the Rio Changuinola in Panama, completed) in the La Amistad watershed is not warranted. The World Commission on Dams (2000) defines a “large” dam as one over 15 m. high – a very different situation from that found on the Rio Genio. 3. TEMPERATE ZONE FISH PASSAGE STRUCTURES FOR DIADROMOUS SALMONIDS The largest body of experience with fish passage structures as mitigation for dams is with the Pacific salmons, principally in the Pacific Northwest region of the United States and Canada. Engineers and biologists attempting to design passage facilities for salmon have several advantages over their counterparts in the tropics: Compared to most tropical diadromes, salmon are relatively large bodied both as adults and downstream migrating juveniles. Biologists can draw on an abundance of life history and behavioral studies covering a relatively non-diverse group of species. And because of the economic importance of salmon, it is far more likely that the necessary investment in design and construction of passage structures will be secured, and that they will be monitored and maintained in operable condition. However, this economic importance has led to the neglect of other, commercially insignificant diadromes in planning for fish passage facilities (Helfman, 2007). Helfman (2007) provides an excellent overview of the roles of lack of adequate life history information, poor design, shoddy construction and prioritization of public relations over actual conservation goals in the long record of total or partial failure of dam site mitigation measures for diadromous fish. Francfort et al. (1994), Orsborn (1987), Petts (1984) and Williams (2006) document the spotty record of mitigation efforts. The National Research Council (1996), Ferguson et al. (2005) and Williams et al. (2005) all conclude that even in the best cases survival of migrants has been severely impacted. 4. SPECIAL CONSIDERATIONS IN TROPICAL RIVERS In contrast, anyone seeking to design fish passage facilities for tropical diadromes, such as the species found in the La Amistad World Heritage Site, faces a series of obstacles. The following considerations greatly reduce the utility of temperate zone experiences as models for fish passage facilities in the tropics.

• In tropical streams, most of the migratory species are small and, even in the case of the larger fish species, part of the migratory pattern involves very small juveniles, larvae and even passively drifting eggs.

• As mentioned above, the state of life history information for the various species ranges from near-zero to substantially incomplete. This factor alone renders the designer’s chore speculative. Any passage facility for any of these species should be labeled as “experimental”.

• Even on the basis of incomplete knowledge, the diversity of behavior and ecological requirements is daunting. While all of the salmons are anadromous, tropical diadromes

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exhibit all 3 forms of diadromy –anadromy, amphidromy and catadromy (see footnote in page 4). To cite the most obvious examples –a large, powerful swimmer (e.g. Joturus pichardi), a medium size climber (most of the shrimp) and a tiny, passively drifting egg require different kinds of passage facilities.

• The economic incentive present in the case of the salmons is lacking. • In contrast to some North American situations, in most of Latin America there is little

hope of design research or construction of fish passage facilities being subsidized by the national governments.

5. SHRIMP PASSAGE FACILITIES IN GUADELOUPE The only attempt to provide passage facilities for tropical diadromes similar to those found in La Amistad of which we are aware is from Guadeloupe, where efforts were made to provide passage facilities for 3 species of diadromous shrimp, each with a different climbing regimen, and one of which supports an economically important fishery. Of the 3 species the Atyid Micratya poeyi was totally blocked by the passage structure which was ultimately built. Fievet (1999) observed that a fraction of individuals of two other shrimp species, the Xiphocarid Xiphocaris elongata and the economically important Palaemonid Macrobrachium faustinum succeeded in passing upstream. He did not provide data on downstream movement by returning adults or newly hatched larvae. Fievet (2000) termed the results biologically marginal and economically inefficient. 6. HISTORY OF FISH PASSAGE FACILITIES IN BRAZIL The only relevant information on attempts to evaluate passage facilities for tropical fish comes from Brazil, where attempts to assist migratory fish around dams date back to 1911 (Godoy, 1985) and where construction of such facilities is mandatory in much of the country (Agostinho et al., 2008). While the ichthyofauna in question is largely potamodromous (migrating entirely within fresh water) the biological diversity of the species in question is greater than that for the La Amistad area, and creates similar design difficulties. It should be noted that while in Brazil, as elsewhere, the original motive for development of fish passage facilities was undoubtedly genuine, it soon became a mere requisite, approached more as an engineering and budgetary challenge than as a biological tool.

Only recently have the results begun to be carefully monitored. In Brazil, as elsewhere, the traditional criterion of success is whether or not upstream migrating adults of the target species are observed to successfully navigate the facility in appreciable numbers. Downstream movement, necessary to complete the cycle, is rarely monitored, thus there generally has been no clear evidence as to whether passage facilities are contributing to survival of migratory stocks in the long run. Pompeu et al. (2011) review the history of fish passage facilities in Brazil, and offer little reason for optimism. Before describing their results, we should note an essential difference between the Brazilian situation and that which obtains in Mesoamerica and the Caribbean,

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including the La Amistad area. With diadromous animals, successful passage between marine and freshwater environments is absolutely essential to population maintenance; the only alternative is extirpation. In the case of species entirely confined to fresh water, a likely result of damming is range fragmentation which may lead to local extirpations, but normally with a less precipitous rate of decline and a lower probability of watershed-wide extirpation. Emphasis in the discussion which follows is not on survival of Brazilian species, but on the effectiveness of fish passage facilities in performing their intended function.

Pompeu and Martinez (2006) concluded that while “there is variation in fish ladders . . . in general, approximately half the fauna that enters the mechanism does not reach the end.” Of those fish which do successfully navigate fish ladders, most probably do not return downstream. Agostinho et al. (2007) conclude that “rheophilic2 behaviour likely precludes downstream migration through large dams and reservoirs”, so that fish passages may constitute “a one-way route that promotes upstream movements of migrants, without the necessary return of adults or their offspring”. That is, large expanses of lentic habitat with no perceptible current, as occur in artificial reservoir lakes, do not permit fish to orient themselves for downstream migration.

Similarly, Freitas et al. (2009) cite “evidence that drifting eggs and larvae disappear in

the lentic areas of the impoundments, and do not reach the dam” (Pompeu et al., 2011). Overall “there is consensus that fish passes built to promote upstream passage cannot provide downstream passage.” (Larinier and Travade, 2002)

Part of the problem, documented principally in the North Temperate zone, but

undoubtedly applicable in the tropics, is that even when bypasses are available for downstream migrants, fish may actively seek out or be trapped into passing through the turbines of the dam, often occasioning high mortality (Kraabol et al., 2009, Cada et al. 2006, Coutant and Whitney, 2000, Schilt, 2007).

The Brazilian experience is not atypical; the “success” of fish passage facilities is normally evaluated by counting the number of individuals of target species which use them to facilitate upstream movement. Thus, the ultimate effect of fish passage facilities for some species may be as “sinks” (Godinho and Kynard, 2009) or ecological traps (Pelicice and Agostinho, 2008), but a majority of species may not even use them. In a study of 13 Brazilian dams, Agostinho et al. (2002) found that in no case did more than 44% of fish species found below a dam enter the fish passage facility. In none of the extensive Brazilian literature is there any report confirming that a fish passage facility has adequately performed a mitigation function. This may in part reflect a failure to monitor hypothetically occurring downstream migrations (Kraabel et al., 2009, Cada and Francfort, 1995; Agostinho et al. 2004). However, Pompeu et al. (2010) conclude that “The few studies evaluating fish passes in South America have indicated problems related to their functioning, such as selectivity in providing upstream passage and the virtual absence of downstream migration”. The enormous differences between upstream and downstream natural migrations mandate separate structures to facilitate downstream movement, yet we are not aware

2 Orienting to flow

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of a single instance where any attempt has been made to provide for downstream passage of any tropical diadromes. In Brazil, fish passage facilities have been evaluated as ineffective in conserving migratory species (Godinho et al. 1991; Oldani, et al (2007), and in some cases are considered to have contributed to regional fishery collapse (Lopes et al., 2007; Pelicice and Agostinho, 2008) by enticing and trapping upstream migrants in reservoirs. In a context of diadromous migration, where there is no possibility of sustaining remnant populations in fragmented habitat, the result of ineffective fish passage facilities can only be worse. 7. CONCLUSION In a summary report on “fish passage at small hydro sites” Therrien and Bougeois (2000) state that considerations about fish passage efficiency should include all of “the species of interest, the number of obstacles in the river and their location and the biological objectives of the project”. In the case of the La Amistad watersheds, all of the species in the rivers, or at the very least those diadromes known to range upstream of the World Heritage Site boundaries, are “of interest” and the biological and conservation objective should be to preserve the conditions which permit their survival in the World Heritage Site and its downstream watersheds. Thus the burden of proof is on dam proponents to show that they can offer such protection. We have shown that at this time there is no reason to believe that preservation of the World Heritage Site ecosystem is compatible with building dams in Panama and Costa Rica as has been proposed. As much was admitted by AES and MWH (2009) in their proposal for a mitigation strategy for the CHAN-75 dam (subsequently completed with no fish passage facility). There they stated that “The construction of a fish passage facility is not an adequate means of mitigation for the Changuinola project”. We conclude that there is no real reason the question of mitigation should even be on the table for the La Amistad watershed dams. Dam proponents should be willing to defend the thesis that the economic benefits which would presumably be derived from building the dams, justify abandoning the commitment to biodiversity conservation implicit in National Park, World Heritage Site and Biosphere Reserve status and more than compensate for loss of biodiversity and other negative environmental, cultural and local economic impacts. Addition of ineffectual fish passage facilities will only increase the economic cost of destructive dams in the La Amistad watersheds.

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