The Aquatic Exodus: An Overview of Migratory Species in Jamaican Freshwater Systems

Prepared by

Ms. Kimberly John

Freshwater Conservation Specialist

The Nature Conservancy

&

Ms. Aisha Bailey

Volunteer - Freshwater Conservation

The Nature Conservancy

Introduction Two mass migration events were recently reported in the Jamaican media (Daily

Observer, January 9 th , 2006 and Jamaica Gleaner November 25 th , 2005). Both involved the natural migration of freshwater species from the sea to upstream areas in rivers.

Active migrations within river systems are not usually noticed or recorded by scientists and locals in Jamaica (although they used to be a regular part of our rural culture).

Consequently, the migrations of freshwater gobies between November 2005 and

January 2006 sparked some temporary curiosity in the Jamaican public. What was not publicly emphasised at the time was that these were not rare, unnatural or ominous events. On the contrary the migration of many of Jamaica’s freshwater species from upstream areas to the sea and vice versa is a regular natural occurrence and an important facet of healthy, functional, aquatic ecosystems. This article aims to provide general ecological information on migration in Jamaica’s rivers -a virtual aquatic exodus- repeated over millennia across the island. This overview will hopefully provide scientists and non-scientists alike with some insight into this fascinating aspect of

Jamaica’s natural history and set us thinking more critically about how our activities impact freshwater ecosystems.

Figure 1: Front page of the Daily Observer, January 9th, 2005 - Spectators watch the upstream migration of thousands of juvenile gobies ( Sicidium Plumieri ) at the Yallahs fording.

Ecology of migration

Baker (1978), defined migration as the act of moving from one spatial unit to another. In ecological studies many kinds of migrations are described; from accidental to non - accidental, home range to navigational and latitudinal to altitudinal migrations. Se asonal migration -migration that corresponds with changes in seasons - is the most common interpretation of the term “migration”. Reproductive migration is a type of seasonal migration in which move to other places or habitats in order to bear and/o r raise young. Relocation occurs generally in order to protect young from predators or other environmental stresses or because the needs a different kind of habitat for that particular life cycle stage. This article deals specifically with the reproductive migratory patterns of Jamaican freshwater fauna.

Freshwater reproductive migration is classified based on the capacities of freshwater species to cope with waters of varying salinities during specific stages in their life cycles

(McDowell 1988). Species that complete their entire life cycle within freshwater systems

(feeding and breeding grounds often being several kilometres apart) are known as potadromous species. Of even greater significance to freshwater and evolutionary ecology are those species whose life cycle takes place partly in freshwater and partly in sea water. These are called diadromous species. Two groups are distinguished among diadromous species. Anadromous species, for instance the well-known Atlantic salmon

(Salmo salar ), reproduce in freshwater while the growing phase occurs in the sea.

Catadromous species, the American Eel ( Anguilla rostrata ) for example, migrates to the sea for breeding and then migrate to freshwaters for growth and trophic purposes.

Jamaica’s Freshwater Migratory Fauna

This article is by no means an exhaustive survey of migratory species in Jamaican rivers. However we will highlight some of the more prominent travellers in Jamaican streams which have adapted to incorporate both freshwater and marine habitats into their life cycles. Among these are fish such as mountain mullet, gobies and the

American Eel, and invertebrates for instance shrimp (janga) and the locally called bussu . Mullets

Figure 2: Young mountain mullet caught with hand

Agonostomus monticola (mountain

Mugilidae (mullets). It is a pelagic fish that occurs in high neo-tropical regions such as Mexico, Central America and the West Indies. Mullets have been recorded in th e Swift, Buff Bay and Yallahs Rivers in Jamaica, although their distribution is probably widespread. Aiken (1998) reports that a relatively familiar species in Jamaican streams, but highlights the limited knowledge regarding its bi ology and ecology. Mountain mullets appear to be a catadromous species migrating to the sea from freshwater to spawn. Several reports of mountain mullets in other Caribbean rivers note the presence of spent individuals and the absence of gravid females in the rivers coupled with the presence of larval forms in sea with a simultaneous migration of spent individuals back to the rivers which suggest that these mullets breed in sea water. It is postulated that the spawning period of the mountain mullet coincides closely, but not always, with the rainy season.

Gobies

The upstream migration of (Sirajo goby) (locally known as

‘suckstone’) in Great and Yallahs Rivers was recently captured in Jamaica’s print and electronic media (figure 1) . Sicydium plumieri is a dermersal anadromous fish belonging to the family Gobiidae (gobies), and subfamily . They are distributed mainly in the subtropical freshwaters of Central America and the West

Indies. S. plumieri post-larval migrations have been noted across the Caribbean. The post-larvae are a local delicacy in Puerto Rico, Guadeloupe, Dominica and Martinique where they are called “ceti” and in Jamaica where they are known as “fryers”.

Sicydium adults spawn in headwaters where females deposit their eggs on the substratum under supporting structures such as boulders, stones and crevices or even among vegetation. The eggs are attached to these structures with adhesive filaments.

These eggs are then fertilised by the male gobies which also protect them from predation. After about two days the eggs hatch and the larvae drift downstream.

Spawning occurs in every month of the year but peaks during the rainy seasons when the increased volumes of the river water carry the larvae downstream to the river mouth.

It is in these brackish or marine environments that the larval and post-larval stages remain for one lunar month. At about the last quarter of the moon phase, post-larvae appear along the sea shore as they approach the river mouth. The post-larvae then metamorphose into juveniles.

Upon completing the juvenile stage the fish aggregate in large numbers and set out on the journey back to the headwater regions of their ancestors. They normally move inconspicuously below the water surface. However in areas where the channel is constricted, - such as the Great River Dam or Yallahs Fording- massive shoals of these young fish become visible as they congregate along the banks, walls and boulders.

These goby juveniles have specialized pelvic discs and tails that are used to climb physical barriers, even outside of the water, in order to migrate upstream.

American Eel

The American Eel ( Anguilla rostrata ) is a catadromous fish, outstanding because of the scale of its migration and the morphological and physiological changes that occur during its life. A. rostrata is distributed across coastal areas and streams in the West Atlantic, from Canada in the north to Trinidad in the south. It occurs in Jamaica, however its specific distribution across the island is unknown (We have observed a child catching an eel in upper Rio Grande with a simple hook and line). The eel’s life cycle begins with spawning Sargasso Sea in the south-west Atlantic. Sexually mature eels migrate from streams across their range for this annual mass spawning event between February and

April. It is assumed that adult eels die after spawning. The first stage in the life cycle, called a leptocephalus, drifts and swims towards the continental shelf where it metamorphoses into a “glass eel” because of its transparency.

Figure 3: Diagram of A. rostrata 's life cycle. (taken from Communications D irectorate Fisheries and Oceans Canada, 2000)

Upon reaching coastal areas, glass eels become pigmented and are known as

“elvers ”. Many elvers swim upstream into rivers and streams in search of less crowded or better quality habitat and replace eels that have already matured and left the river.

However, a proportion of the elvers remain in estuaries. Elvers mature into adults which are called “yellow eels”. A. rostrata may remain in freshwater ecosystems for up to 15 years before sexual maturity and embar king on the spawning migration.

Freshwater shrimp

Invertebrate freshwater species are also common migrants in Jamaican rivers. There are several species of migratory shrimp in Jamaica (Hunte, 1978) usually belonging to the Palaemonidae family. Macrobrach ium , commonly called Janga by locals, is one migratory palaemonid which is relatively abundant in Jamaican rivers. These organisms are generally subtropical and are very important for nutrition, recreation and commerce throughout the Caribbean.

Figure 4: Macrobrachium spp in Rio Grande tributary. R. Love.

Macrobrachium spp. are anadromous spending most of their life cycle in freshwater streams while larval stages reside temporarily in estuarine waters. Gravid females remain in stream headwaters and release planktonic larvae which drift downstream to estuarine regions. The larval stages remain planktonic for approximately 12 weeks after which they begin to metamorphose into juveniles. The juveniles are benthic and migrate upstream into freshwater. Hu nte (1980) and March et al (1998) noted that release and hatching of eggs and larval drift occurred during the night so as to reduce the effects of predation and hence decrease larval and juvenile mortality.

Bussu ( punctulata )

The gastropod Neritina punctulata is yet another migratory invertebrate present in

Jamaican streams. These snails belong to the family are quite abundant in tropical regions such as Indo -Pacific islands and the Caribbean. In the Caribbean neritids have been found in Jamaica, Dominican Republic, Dominica, Costa Rica,

Guadeloupe, St. Lucia, St. Vincent and Martinique. In Jamaica N. punctulata has some nutritional and economic value and is traditionally harvested in northern Blue Mountain streams. However, its exploitation may be increasing with commercial harvesting in support of events such as the annual Bussu Festival held in Portland parish.

N. punctulata has a similar anadromous migratory pattern to Sicydium and

Macrobrachium . The female snail lays her eggs in streams. The eggs hatch after 20-22 days and the planktonic larvae produced are carried to estuaries or the sea where they develop into juveniles for approximately one year. These juveniles then migrate back to the freshwater systems. Other observations also suggest that some neritids migrate back to freshwater ecosystems as larvae, attach to substratum and then continue their development. Several studies regarding the downstream and upstream migrations of neritid snails have been conducted. However until recently mass or gregarious migrations of snails have not been described. Schneider and Frost (1986) described the mass upstream movement of juvenile neritids in a Costa Rican stream and it would be interesting to investigate whether these kinds of migrations occur in Jamaican streams.

Conservation Implications of Aquatic Migration

Migratory aquatic species are highly dependent on the characteristics of the different aquatic environments that support specific stages in their life cycle as well as the ecological corridors that maintain connectivity between these habitats. In Jamaica, this has implications for how we manage freshwater and marine ecosystems as well as the estuarine areas in between.

The fact that there are important aquatic species utilising entire river systems and estuaries highlights the need for a more holistic approach to the conservation of freshwater ecosystems in Jamaica- beyond our attempts at controlling water pollution and protecting upper watersheds. First and foremost we need information on the distribution, ecology and status of migratory freshwater species. This remains a huge data gap that can only be filled through focussed and systematic scientific research into migratory aquatic species. We must also generate information on how activities that have been shown to be detrimental to migratory species in other countries, such as dams, affect our own fauna. However, Jamaica cannot wait for all the necessary scientific information before taking conservation action. We can begin now, to manage our freshwater ecosystems based on the available data and sound ecological principles.

For example, there is some evidence that dams and hydrologic stations are common obstructions to migratory species in Caribbean rivers (Benstead et al 1999). Ideally we should assess whether our old dams presently allow aquatic fauna to pass them on their way upstream. However, at a minimum we should ensure that new dams and fordings are constructed with passages and fish ladders. It appears that a significant proportion of migrations that occur in Jamaican streams follow seasonal or even diel

(daily) patterns. Surely we can take this seasonality into consideration during sand mining and river dredging. These seasonal patterns may also have implications for the harvesting of freshwater biodiversity particularly in light of the increasing popularity of

“crayfish” (shrimp) and “bussu” festivals in Portland.

An interesting detail about migratory freshwater species that we have encountered is the fact that all these species have evolved from families that are or were entirely marine. Therefore the capacity of these populations to inhabit inland freshwater systems and become entirely established is a fascinating evolutionary and biogeographical phenomenon in the insular Caribbean. Hopefully in the future we will incorporate such intriguing scientific information on aquatic migrations, and other ecological processes in everyday affairs like collecting water, discarding waste-water, constructing dams and diversions and harvesting freshwater animals for food and sport.

Acknowledgements :

We would like to thank Dr. Eric Hyslop of the Department of Life Sciences, University of the West Indies, for the literature and information that formed the basis of this article and particularly for his time in checking for accuracy. Thanks also to Dr. Karl Aiken of the same department and to the many rural Jamaicans who have shared their information on freshwater biodiversity over the years.

References  Aiken, K.A, (1998) Reproduction, diet and population structure of the

mountain mullet, Agonostomus monticola in Jamaica, West Indies .

Environ. Biol. Fishes 53:347-352, Netherlands.  Benstead, J.P., March, J. G., Pringle, C.M., Scatena, F.N. (1999) Effects of a

Low-Head Dam and Water Abstraction on Migratory Tropical Stream

Biota , Ecological Applications , Vol. 9, No. 2

 Baker, R. Robin. 1978. The Evolutionary Ecology of Animal Migration .

Holmes & Meier Publishers, Inc. New York.

 Bell, K. N. I. & Brown, J. A., 1995. Active salinity choice and enhanced

swimming endurance in 0 to 8-d-old larvae of diadromous gobies,

including Sicydium punctatum (Pisces), in Dominica, West Indies .

Marine Biology 121 : 409-417.

 Communications Directorate Fisheries and Oceans Canada (2000). Ottawa,

Ontario. www.dfo-mpo.gc.ca

 Daily Observer , Front Page Caption, January 9,2006

 Erdman, D.S., 1986. The Green Stream Goby, Sicydium plumieri, in

Puerto Rico . Tropical Fish Hobbyist , TFH Publication, New Jersey

 Fievete. E. & Leguennec, B., 1998. Mass Migration of Sicydium spp.

(Gobiidae) in the Streams of Guadeloupe Island (French-West Indies)-

Implications for the Derivation Race of Small Hydroelectric Power-

Stations . Cybium 22 : 293-296

 Gross, M. R., Coleman, R. M., McDowall, R.M, 1988. Aquatic Productivity

and the Evolution of Diadromous Fish Migration .

 Hepburn, Monique, “Migratory Eels Spark Renewed Interest”, Jamaica

Gleaner , November 25, 2005  Hunte, Wayne (1978) The distribution of freshwater shrimps (Atyidae and

Palaemonidae) in Jamaica . Zoological Journal of the Linnean

Society 64 The Linnean Society of London.

 Hunte, W., 1980. The Larval Development of the Shrimp . Caribbean

Journal of Science 15 : 3-4

 Keith, P., 2003. Biology and ecology of amphidromous Gobiidae of the

Indo-Pacific and the Caribbean Regions . Journal of Fish Biology 63 : 831-

847

 Larinier, M., 2000. Fish Migrations and Dams . World Commission on Dams

 March J. G., J. P. Benstead, C. M. Pringle and F. N. Scatena, Migratory drift

of larval freshwater shrimps in two tropical streams, Puerto Rico. Freshwater

Biology 40 : 261

 Martin, T. R., 2004. Aspects of the Biology Neritina punctulata

() in two Portland Rivers

 Migration Basics . February, 2006. Online. Internet.

http://www.nps.gov/akso/ParkWise/Students/ReferenceLibrary/general/Migrati

onBasics.htm . National Park Service U.S. Department of the Interior

 Pyron, M. & Covich, A.P., 2003. Migratory Patterns, Densities, and Growth

of Neritina punctulata Snails in Rio Espiritu Santo and Rio Mameyes,

Northeaster Puerto Rico . Caribbean Journal of Science Vol. 39 , No. 3: 338-

347

 Schneider, D. W. & Frost, T. M., 1986. Massive upstream migrations by a

tropical freshwater neritid snail . Hydrobiologia 137 : 153-157

Contact Information Name: Kimberly John Email: [email protected] & Name: Aisha Bailey Email: [email protected]

Mailing Address The Nature Conservancy - Jamaica Unit 5 32 Lady Musgrave Road Kingston 5, Jamaica (876) 978-0766