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Copy of Janitor Fish Pterygoplichthys disjunctivus in the Agusan Marsh: a Threat to Freshwater Biodiversity
Transcript of Copy of Janitor Fish Pterygoplichthys disjunctivus in the Agusan Marsh: a Threat to Freshwater Biodiversity
The janitor fish are considered threat to freshwater biodiversity.
Their wide distribution in the Marsh may lead to an increase in their number rapid enough to displace the native fish species in that area.
The greater their number, the greater their contribution to water turbidity and soil erosion.
They also cause socio-economical damage such as destruction of fishing gears.
Janitor Fish Pterygoplichthys disjunctivus:
a Threat to Freshwater Biodiversity
Practical control measures to reduce their population were discussed.
A BIO8 report
Ann Marjorie Luz
shelly Monique Petras
Knizza Valerie Tan
Darwin Philip Teh
RESULTS AND DISCUSSION
More studies in the Marsh have yet to be conducted
The lack of study of the freshwater biology in the area leads to the apprehension that the presence of janitor fish may change the present aquatic faunal composition before this can be fully studied
The purpose of this study is to gather baseline information on the following:
taxonomy, distribution, pupulation and biology of the janitor fish
their possible impacts on freshwater biology
invasive alien species: species that are non-native that cause a natural disturbance to the habitat to which they are introduced
Pterygoplichthys disjunctivus belongs to Family Loricariidae (Order siluriformes), the largest catfish family with 80 genera and 680 known species
This family is characterized by large dorsal fins with 9 or more dorsal fin rays, presence of adipose fin, and an enlarged stomach connected to the dorsal abdominal wall
They can also be recognized through a ventral, suctorial mouth, jaws that are designed for rasping along submerged surfaces and a long gut
Locariids with 10 or more dorsal fin rays belong to the genus Pterygoplichthys (sailfin catfish)
RESULTS AND DISCUSSION
POSSIBLE IMPACTS TO FRESHWATER BIODIVERSITY
The Pterygoplichthys could become widely establishd in Southeast Asia and cause an alteration of food web dynamics.
Large populations can alter the energy budget of a water body by reducing the amount of energy available to other herbivores such as aquatic insects and arthropods.
This, in turn, will cause reductions in the populations of other animals who feed on arthropods.
Some economically important fish species in the marsh share similar habitats and food with the P. disjunctivus.
This indicates overlapping food choices and a higher competition for food.
Non-living organic fractions (e.g. detritus) are essential to organisms in the Marsh because they are the principal source of nutrition for primary consumer fishes.
RESULTS AND DISCUSSION
ENVIRONMENTAL AND SOCIO-ECONOMIC IMPACTS
Their burrowing behavior in river banks may contribute to water turbidity and soil erosion.
High water turbidity alters the amount of light that can pass through the water column, thus slowing down photosynthesis.
They cause destruction of fishing gears such as gillnets, subsequently destroying the livelihood of the Manobos.
P. disjunctivus now comprises the bulk of their catch.
Their gillnets, designed for tilapia, common carp and giant gourami, now end up catching more janitor fish.
PROPOSED MANAGEMENT SCHEMES
Conduct long-term assessment to monitor the status of janitor fish in the Agusan Marsh
Purchase janitor fish catches from the fishermen (through the provincial government) by companies that can use them as raw material for leather, feeds and fertilizer.
Make use of the janitor fish for home and office decor.
Strengthen the enforcement of wildlife and environmental laws in the country.
For home and office decor
The fish will be preserved with 10% buffered formalin for two weeks, dried under the sun for a month, then dipped in natural plum dye to make it more attractive.
The primary aim of the study is to verify reports on the presence of invasive alien catfish, locally known as janitor fish, and their possible impact on freshwater biodiversity in the Agusan Marsh.
The study employed procedures such as morphological analysis, field sampling and questionnaire surveys in order to determine the exact taxonomic status, distribution and the population and size estimates of the fish.
Results showed that Pterygoplichthys disjunctivus, a species earlier reported from Laguna Lake and nearby rivers in Luzon, had invaded the Agusan Marsh, resulting in a 0 to 146 individuals caught per fishing trip.
Janitor fish: local term for the South American vermiculated sailfin catfish
popular among fish hobbyists because of their ability to graze and remove attached algae and detritus on the aquarium tank, keeping the surfaces and sand clean, hence the name
Pterygoplichthys disjunctivus: scientific name of the species
Agusan Marsh: a protected marshland in Agusan del Sur, Mindanao; locale of the study
Invasive species are considered a threat to aquatic ecosystems worldwide.
They have been known to cause dramatic changes in species diversity, abundance and energy flow
About 80% of the world's endangered species are at risk due to non-native species introductions.
In the Philippines, well-known cases of biological invasion are the freshwater fishes that have been introduced to freshwater habitats.
310 out of 3, 100 fish species (10%) are freshwater fishes
221 (72%) of these are native
46 (15%) are endemic
38 (12%) are introduced
5 (1%) are questionable or not established
There had been several instances of introduction of non-native species in the Philippines.
In the 1980s and 1990s, the Nile tilapia (Oreochromis niloticus) was introduced. (the most alarming instance of aquatic invasion)
In Lake Lanao in Lanao del Sur, more than 15 endemic species of carp were displaced.
This was further hastened by the introduction of Glossogobius giurus and Micropterus salmoides.
After the 1950s, the South American sailfin catfish (Pterygoplichthys disjunctivus) and P. pardalis were caught in the Laguna Lake and nearby rivers.
Their introduction was most probaby caused by aquarium release and aquaculture farm escape
In 2002, there were reports tof a rise in catfish population and their alleged responsibility for the decline in fishery catch.
Recently, P. disjunctivus was reported in the Agusan Marsh
Probably through an international release within the Agusan Marsh Wildlife Sanctuary (AMWS) or fish farm escapes upstream near Davao sometime between 2002 and 2005
The Agusan Marsh is one of the largest marshlands in Asia
It is endowed with seven biologically important habitats
75% of the country's extracted timber comes from this area.
It is home to several endemic species of mammals, birds, reptiles and amphibians
It is also home to an indigneous group, the Manobos
DESCRIPTION OF THE STUDY AREA
The Agusan Marsh is a protected marshland in Agusan del Sur, Northeastern Mindanao.
A complex of marshes, water courses with small shallow lakes and ponds.
For the purpose of the study, the ArcGIS 9 (based on the forest and land use plan of the DENR) was used to determine the area of the Marsh; total marsh area is 113, 000 hectares, 110, 000 hectares based on topography, 40, 868 hectares on protected area and 14, 835.9 hectares based on the declared protected area of the Ramsar Convention on Wetlands.
Sampling was conducted by local fishermen using gillnet from April to July 2006
Fishermen recorderd the fishing ground, the number of janitor fish caught and the longest lengths of the janitor fish caught.
The external morphology of the fish was examined.
body shape, mouth type, type of teeth, type of caudal peduncle, body color, total length, number of anal and dorsal fins and other distinguishing characters
IDENTIFICATION OF HABITAT AND DISTRIBUTION
Questionnaire surveys were coinducted in the nine municipalities of Agusan del Sur.
Habitat and distribution of the janitor fish were described and tabulated.
POPULATION AND SIZE ESTIMATES BASED ON CATCH DATA
A 12-hr fishing trip for janitor fish was conducted by local fishermen in coordination with the barangay captain and local officials using gillnet
Conducted from April to July 2006 in the following sites
San Jose and Poblacion, Sta. Josefa
Sabang-Adgawan, La Paz
Katipunan, Osmena and Villa Paz, Loreto
Nueva Era, Bunawan
Fishermen recorded the fishing ground, janitor fish catch, and the smallest and longest lengths (total length) of the janitor fish caught
Catch data was tabulated and the fishing grounds were classified as downstream, midstream and upstream areas
Mean and total janitor fish catch were obtained
IDENTIFICATION OF POSSIBLE IMPACTS ON FRESHWATER BIODIVERSITY
Possible impacts were determined by comparing the habitats and diet composition of economically important fish species with that of the janitor fish.
Other environmental and socio-economic impacts were also discussed.
Proposed management schemes for the species were also included and discussed.
External morphological analysis showed that the janitor fish in the Agusan Marsh is Pterygoplichthys disjunctivus, as confirmed by Dr. Jonathan Armbruster (Auburn University, Alabama, USA)
It has a long, tapered, dark brown body covered with rows of armor plating
Nearly all spots on the abdomen coalesce to form vermiculations
It has a sucker-mouth with villiform teeth
The caudal penduncle is short but slightly broad with an adipose fin and a forked caudal fin with one lobe longer than the other
It has one dorsal spine and 12 dorsal soft rays.
Can tolerate adverse climactic conditions
Their morphological features make them difficult to prey on
With the absence of natural predators, they can multiply fast and out-compete native fish and organisms
HABITAT AND DISTRIBUTION
The results of the questionnaire surveys conducted in the 9 municipalities showed that the janitor fish inhabits lakes, rivers and creeks, but not the peat forest and mixed swamps.
The janitor fish was probably introduced through an international release within the Agusan Marsh Wildlife Sanctuary (AMWS), and possibly fish farm escaped upstream (near Davao) possibly between 2002 and 2005.
With no natural predators in the Marsh, they continued to proliferate, reaching several areas in Agusan del Sur such as Talacogon, La Paz, Loreto, San Francisco, Rosario, Bunawan, Trento, Veruela and Sta. Josefa.
QUIZ TIME! :P
Based on the article reported, why is the janitor fish considered an invasive species?
Enumerate the methodologies used by the researchers in studying the janitor fish? Explain how these methodologies help them in their research.
Based on the findings, what management schemes were proposed to address the problems caused by the janitor fish in the Agusan Marsh?
What is the name of the doctor from Auburn University, Alabama, USA who identified the morphological structure of the janitor fish?
Good luck! BWAHAHAHA
POPULATION AND SIZE ESTIMATES ON CATCH DATA
Were obtained from catch and length data
The upstream and downstream areas have the highest number of janitor fish
the midstream area may be the possible site of introduction or release
The midstream area has the lowest number of janitor fish