Madagascar 2008 – Report from the Field
Madagascar 2008 – Report from the Field
Written by Sunday, 30 November 2008 00:00
The primary focus of my 2008 field season was to secure specimens of the Tsiribihina basin Pachypanchax, the southernmost known population of this genus in the hope that additional material from this locality would help clarify the conservation status of Pachypanchax nuchimaculatus. This species is known only from a unique type specimen of unknown provenance. A previous visit to Miandrivazo in 2004 to collect adult specimens of this Pachypanchax, represented in the collection of the Museum National d’ Histoire Naturelle in Paris, was not successful. The fish was not to be found in either the main channel of the Tsiribihina or its tributary, the Mania. Nor were efforts to find in three of the Miandrivazo region’s numerous lakes, whose fish fauna consisted exclusively of exotic species. The goal of this year’s trip was to sample smaller streams in the vicinity of Miandrivazo at a higher altitude and to investigate suitable low altitude habitats accessible from the town of Belo.
I was unable to find Pachypanchax in either region. Of the seven accessible streams situated to the east of Miandrivazo, four were dry, two were the sites of intense gold panning activity and carried such heavy silt loads as to preclude the survival of any fish and one was isolated from lower altitude habitats by a 30 m high waterfall and contained no fish at all. Fishermen who claimed to recognize photos of other Pachypanchax species brought me specimens of a mullet species and the goby Awaous macrorhynchus. An older woman, whose reaction to my album of photographs indicated a very thorough knowledge on native Malagasy fishes recognized photographs of other Pachypanchax species and unambiguously differentiated them from the mullets caught by other fishermen. She indicated that Pachypanchax had been present in the Miandrivazo region when she was a girl, but that they were no longer to be found. As all suitable Pachypanchax habitats in the region either no longer hold water on a permanent basis, are infested with exotic species or have been converted into rice fields, there is no reason to disbelieve her.
Collecting in the Belo region was likewise unproductive. Collecting in the main channel of the Tsiribihina yielded two species of mullet, Leiognathus equulus, Oreochromis niloticus, Glossogobius giuris and Awaous macrorhynchus but no Pachypanchax. As in the Miandrivazo region, local lakes are dominated by exotic species, among them Gambusia holbrooki and Channa maculata, predators of juvenile and adult Pachypanchax respectively. According to my topographic maps, there should have been extensive marshes in Belo region that could provide suitable Pachypanchax habitat. Unfortunately, the maps in question were printed in the late 1960’s and do not reflect present patterns of land use. The areas indicated as marshes on the map are now rice fields and the only fish found in the canals feeding them were tilapias and G. holbrooki. While it is disagreeable to contemplate the disappearance of any species, in light of these facts I am forced to conclude that the Tsiribihina Pachypanchax is in all probability extinct.
I had originally intended to return to the Anosy and resume last year’s survey of aquatic habitats in that region. My failure to find the Tsiribihina Pachypanchax taken with a report of drought-induced deterioration of aquatic habitats in the Boina region led me to change my plans for the remainder of the 2008 field season. Instead of flying to Ft. Dauphin, I elected to focus on securing sufficient specimens of the undescribed Pachypanchax species native to the Sofia and Doroa-Loza drainages I first collected in 2004 with the object of establishing captive populations of these threatened killifish as assurance against their extinction. Although water levels of Ankaranobe Creek were much lower than they were in 2004, the inhabitants of Ambodibonara Village were able to collect sufficient individuals of the Doroa-Loza Pachypanchax to permit the establishment of a viable managed population. This was particularly fortunate, as villagers also signaled the presence of Channa maculata in the Doroa-Loza basin. According to my field notes, this was not the case in 2004.
Due to the extreme contraction of fish habitat in the Mandritsara region due to several successive years of below average rainfall, securing adequate numbers of the Sofia Pachypanchax proved much more difficult. However, thanks to the invaluable assistance of M. Randriamihavana Florent, the regional representative of WCS’ Makira Project, I was also able to collect sufficient founders of this critically endangered species to establish a viable captive population. It is impossible to overstate the extent to which several years of drought have negatively impacted fish populations in the Mandritsara region. Lakes along the road from Antsohihy to Mandritsara where fisherman working from pirogues were observed in 2004 were rice fields this year. Stretches of the main channel of the Amboaboa River that were three meters wide and a meter and a half deep in 2004 were just over a meter in width and less than 30 cm deep this year. I was able to confirm the presence of only four of the ten species of native fish reported from the Amboaboa River: Sauvagella robusta, Pachypanchax sp./Sofia, Paretroplus nourissati and Awaous macrorhynchus. According to local fisherman, while Paratilapia polleni and Ptychochromis insolitus are still present, they have become extremely rare. Fortunately, both species have been successfully bred in captivity. It has been four years since anyone in the region has caught a specimen of Arius festinus, Rheocles derhami or the recently described Paretroplus gymnopercularis. As efforts to collect these fish elsewhere in the Sofia drainage have been unsuccessful, their apparent disappearance from the Amboaboa is clearly cause for alarm.
The recent establishment of Channa maculata in the Doroa-Loza basin and the ongoing habitat deterioration in the upper Sofia basin has negatively impacted the conservation status of their respective Pachypanchax. I assessed the Doroa-Loza species as Vulnerable in 2004. It must now be considered Endangered. The Sofia species, which met the criteria for Endangered status in 2004 is now clearly Critically Endangered. The inexorable deterioration of their environment makes establishing managed population of these species ex situ as insurance against their global extinction an absolute necessity. This could have been accomplished in 2004 had I been able to export the specimens I was then able to collect. The necessary export permits were not forthcoming and the fish being held at the University of Antananarivo were subsequently lost. We now have a second chance to save these species. If the 2004 scenario is repeated in 2008, conditions in the Boina region make it highly unlikely that we will be afforded a third.
Fortunately, there is also some good news to report from this year’s field season. In its August business meeting, the governing board of the Madagascar Fauna and Flora Interest Group approved a proposal to conduct a headwaters to estuary ichtyofaunal survey of the Ivoloina River. The broad outlines of this effort were established in a meeting with Dr. Eustache Miasa of the University of Toamasina and Dr. An Bollen, the MadFFIG’s Project Manager. This exercise has been tentatively scheduled for mid-October 2009 and will involve both expatriate researchers and Malagasy faculty and students from the Universities of Toamasina and Antananarivo. I also had a productive interaction with students from Dr. Miasa’s GRENE program. I gave them an introductory Power Point presentation on the fishes of Madagascar, some training in basic water chemistry testing and took them out to the Manambolo River for some hand-on training in basic sampling techniques, e.g., how to use fish traps and beach seines. The students were enthusiastic – and very quick – learners. As the exercise yielded a nice series of the undescribed Bedotia species I discovered there a couple of years ago that will allow me to properly describe the beast, it was productive in more than the narrow pedagogical sense.
The other good news from Ivoloina relates to our first attempt to re-introduce an endemic Malagasy fish species to a habitat from which it had disappeared. According to the staff at the Parc Zoologique d’ Ivoloina (PZI), Paratilapia sp./Fony, the East Coast small spot Paratilapia, was formerly present in the streams feeding Lac Coutance, the large impoundment that was created to provide water to the fish ponds on the Zoo grounds. I did not find it during the course of my first visit to the park in 1996, nor was it found when the lake was drained several years later to permit repairs to be made to the dam. As this species had by that time become reasonably well established in the cichlid hobby in North America, I proposed to the governing board of the MFFIG that we attempt to re-introduce Paratilapia sp./Fony to the PZI. This proposal was approved at the 2001 business meeting of the MFFIG. Between them, Louis Rovner and Lou Pochetino of the Mid-Atlantic Cichlid Association and Laif DeMason of Old World Exotic Fish came up with 187 1” – 2 ½” TL juvenile Paratilapia sp./Fony. The fish were duly shipped from New York to Antananarivo on 21 December 2001. The fish made the 23 hour flight with only a single mortality. The staff of the Wildlife Conservation Society’s Madagascar program met the flight at the airport, cleared the fish through Customs and delivered them to the laboratory of my Malagasy colleague, Dr. Noromalala Raminosoa at the University of Antananarivo. Mr. Lanto Andrianamampianina, from WCS’ Antananarivo office and Mr. Tsilavana Ravelomanna, one of Dr. Raminosoa’s graduate students, drove the fish to the PZI on 23 December 2001 and the following day successfully released them into a previously selected grow-out pond.
The original plan was to grow the fish to adult size in a setting where Tsilavana could regularly monitor their growth under natural conditions, then release them into Lac Coutance. This research, supported by a grant from the Denver Zoo, would serve as the basis for Tsilavana’s MSc thesis and provide us with valuable information on the growth rate and survivorship of Paratilapia sp./Fony under more or less natural conditions. Unfortunately, politics and the weather conspired to scuttle this project. Madagascar’s contested 2001 presidential election resulted in several months of turmoil with two competing governments, one headed by president-elect Marc Ravelomanana – a distant relative of Tsilavana – based in Antananarivo, the other, headed by former president Didier Ratsiraka, based in Toamasina, Madagascar’s principal seaport. In its attempt to retain power, the Ratsiraka faction decided to apply economic pressure on the Ravelomanana government by cutting road and rail links between Toamasina and the capital. Thus even had it been safe for Tsilavana to travel to Ivoloina, there was no way for him to do so. Then in May an unprecedented tropical depression dumped a meter of rain on the Toamasina area over a three day period, flooding PZI’s low-lying ponds. This led us to conclude that our Paratilapia had been washed into the Ivoloina River, effectively bringing to an end this first effort at reintroducing a native Malagasy fish to its former habitat.
Over the next few years, park staff reported occasional sightings of Paratilapia in either Lac Coutance or its affluent streams. However, the first tangible evidence that we might have prematurely written off the 2001 reintroduction exercise came in 2006, when an unbaited fish trap caught a 3” TL juvenile Paratilapia sp./Fony in one of the streams flowing into the lake. In January of this year, I received an e-mail from Tsilavana informing me that he had seen breeding pairs of Paratilapia sp./Fony in the lake. During the course of this year’s visit to PZI, I was able to observe a number of adult Paratilapia sp./Fony ranging in size from 5” SL to 8” SL in Lac Coutance. Given that no Paratilapia were found when the lake was drained a decade ago and given what is known of the growth rate of this species under aquarium conditions, it is not unreasonable to conclude that the individuals I saw were survivors of the fish sent to Madagascar in 2001. While the water levels of the 2001 flood were not high enough to afford the fish direct access to Lac Coutance, they would certainly have allowed them indirect access via its outflow. Irrefutable evidence that this species is breeding successfully in the lake came from the capture this September of seven juveniles ¾” to 1½ “ TL in a baited trap set in the shallows.
The story of the Arola River provides a positive close to this account of my 2008 field season. The Arola is a small tributary of the Rianila(?) River that crosses RN-2, the road connecting Antananarivo and Toamasina about 7 km west of the town of Brickaville. When I first sampled it in 1997, it was a quintessential East Coast blackwater stream flowing from an intact Pandanus-Dracaena swamp and supporting extensive stands of the iconic Madagascar lace plant, Aponogeton madagascariensis and Lagarosiphon madagascariensis, an endemic bunch plant. I have collected six species of native fishes from the Arola, which makes it, by Malagasy standards, a fairly species-rich habitat. Although it supported an important trap fishery for the eel Anguilla bicolor, the dominant position of the freshwater herring Sauvagella madagascariensis and the rainbowfish Bedotia madagascariensis in its ichthyofauna testified to the pristine character of the Arola. Both species are intolerant of even low levels of suspended silt and neither occurs under even slightly eutrophic conditions.
The condition of the bridge over the Arola was, to phrase it tactfully, highly questionable when I first sampled the river. It gave up the ghost during the 2003-2004 rainy season. When I visited the Arola in 2004, construction of a new bridge was in full swing and the river was a mess. Its waters both upstream and downstream of the construction site were red with silt, the extensive stands of aquatic plants were gone and the only fish caught were a few Bedotia in very poor condition. According to the local villagers, the construction of the bridge had driven even the eels away. With a heavy heart, I wrote the Arola off as another victim to progress.
When I revisited the Arola this year, I was thus very pleasantly surprised to discover that it had effectively returned to its original condition. Its waters were clear, the extensive stands of aquatic plants were once again in evidence and both S. madagascariensis and B. madagascariensis were back in force! Understandably concerned to prevent damage to the approaches of the bridge from erosion, Colas, the engineering firm contracted to build the new bridge had planted the surfaces exposed during construction with fast-growing ground cover plants. With the influx of silt thus halted, the Arola was able to clear itself. With the return of water clarity, its community of plants and animals rapidly re-established itself from the reservoir of unimpacted populations well downstream of the disturbance.
While the recovery of a speciose and readily accessible aquatic habitat is in and of itself worth celebrating, the full and surprisingly rapid recovery of the Arola has much broader implications. It suggests that at least on the eastern versant of Madagascar, aquatic communities are surprisingly resilient. Assuming the presence of a reservoir of potential colonists elsewhere in a drainage, even a severely disturbed community can be expected to recover once the stressor or stressors responsible for its deterioration have been removed. The ongoing process of upgrading Madagascar’s transportation infrastructure and the expansion of mining activity guarantee that aquatic habitats, particularly on the eastern versant of the island, will be increasingly subjected to disturbances of this sort. That aquatic habitats can bounce back if given the chance makes it essential for conservation organizations to collaborate with the appropriate Malagasy regulatory agencies with the aim of assuring that civil engineering firms and mining companies both operate in a manner that localizes environmental disturbances to the greatest extent possible and make a budgetary commitment to restoring disturbed habitats to their pre-impact conditions.
Photos by the author.
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