Amazon Fisheries Lessons

By Dr. G.F. Hartman

Fish Market worker holds prized Tucanare or Peacock Bass a  fish that can grow to longer than 50 cm and  weigh more than 10kgs!    

Editor’s Note:

Dr. Gordon Hartman was born in Fraser Lake and known the world over as one of the most knowledgeable scientists on any fishery. 
He has a Ph.D. in zoology, was the scientist in charge of a major fish-forestry research project,  held senior positions in the provincial government and the Yukon government; Deputy Minister status in the latter until he asked to be relieved of that role.   He has taught at the university level for about six years (University of Guelph and Addis Ababa University) and spent three years in Africa with CIDA for two, and FAO for one. He thinks he has about 80 publications, scientific, or managerial, or philosophical.  He has submitted several articles to Opinion 250, including  Fraser and Nechako Rivers, Where do We Want to Go?   

THE RIVER

The Amazon is the largest river in the world. If you spread its drainage basin out over our country, it would cover most of western Canada from the west coast to the Ontario boundary. About 20% of all of the river flow in the world runs from this one river. Its mean annual flow is <175,000m³/sec. For a sense of scale, think of the Fraser River, during peak flow it runs at about 9,000 m³/sec at Hope. An un-dammed Nechako would have run at about  200 m³/sec, mean annual flow, above Fort Fraser.

The Amazon has a regular seasonal pulse which begins in October and peaks in the February-March period. During the pulse it may rise as much as 15 m at many locations. Far up the river, in its mid-location, it may spread as wide as 40 km. When we walked in the ‘flooded forest’ areas, we could see the water line 5 me above our heads on the tree trunks.

The total area of river, flooded forest, and ‘floating meadow’ is about 350,000 km2 during the peak of the flood pulse.

When you travel on this river, even at low water, it seems as though you are out on a very wide lake, not a river. In spite of its great width and low gradient, the river moves along at about 7 km/hr.

THE FISH

Jansen Zuanon, a fish taxonomist at Manaus, told me that there are about 2,600 identified fish species in the system. He believes that the total number of freshwater fish species in the Amazon River system may be as high as 5,000. We have a total of about 85 species in B.C., 180 in Canada, and 1,000 in North America. Although there is an enormous number of fish species in the Amazon system, there are only about 120 species that figure strongly in the commercial fishery, around 200,000 tons/yr, in the Amazon.

As a west coast B.C. fisheries person, I was surprised to learn that several species of catfish undergo longer freshwater migrations than any salmon. Some of them migrate from the lower Amazon, near Belém, for about 4,000 km or more up-river to near the east slopes of the Andes Mountains.

There are many fish that are normally considered as marine in the river. These include puffers (Family Tetradontidae), soles (Family Soleidae), needle fish (Family Belonidae), and Amazon stingrays (Family Potamotrygonidae).

There are some fish that are better left alone. The book “Peixes de Lagos do Medio Rio Solimoes” lists nine kinds of Piranhas. These fish do not go about, all of the time, stripping cattle and people of all of their flesh. However, some species of them may attack, in groups, during periods of low water and food stress. Another species, the electric eel, is better left alone. It is up to 2.5 m long with 5,000 or 6,000 electroplaques, which can produce a jolt of 500 volts @ one amp.

Many parts of the Amazon are turbid and low in oxygen. One group of fish there, the Gymnotiformes, produce electrical fields around their bodies. They can sense things in the environment around them by detecting changes in these electrical fields. Because of the low oxygen, many species gulp and swallow air from the surface and extract the oxygen from it as it passes through their intestine.

(At right, a  fisherman stands in his canoe in the "floating meadow" waiting for a Pirarucu to surface, when it does, he will harpoon the  fish)

THE MANAGEMENT OF THE FISHERY

Fishery management in most parts of the Amazon basin is in the hands of local communities. A typical fishing community may be made responsible for managing a group of three or four lakes. With some advice from government agency people, the communities make decisions about the amount of fish that they will catch.

Profits from the fishery are shared by the whole community. The community may have decided ahead of time how it will spend the earnings from the fishery, whether it be for building repair, material for the school, or shared income. We went out with one group of fishermen who harpooned and netted two six foot-long, 200 pound “Pirarucu”. These fish were sold within hours to a buyer. The funds went to the community; the harpoon thrower got the appreciation of the group.

(at left,  fisherman  pulls second 200 pound Pirarucu into the canoe)

Without the elements of individual competition and greed, there is less difficulty in setting limits and controlling the catch. On the other hand, slacking was not acceptable. We were told that the community made sure that all people pulled their weight in the fishing effort.

 In one community that we visited, we were told that all fishing would be stopped on the next day. The lake would be left alone for one year. In another lake, the community determined that that gill netting had cut the stocks of some species down too far. They stopped all gill netting and fished with hook and line only.

They face many difficult questions in managing the fish in the groups of lakes. During the height of the flood pulse the lakes may all be connected together and to the rest of the river system. Given this, to what extent are they actually fishing local populations? They understood this kind of issue. The reaction was to be cautious and conservative in the face of limited knowledge.

As a retired fisheries research scientist (DFO), and before that a manager, I wondered if these folks, with average education perhaps around grade four, didn’t look after the fish there just as well as we do with ours here. Their approach of caution and cooperation, combined with good local knowledge, may make up for their limited technical skill and scientific information.

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