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SUMMARY
Catch and fishing effort in the Upper Meta River System for the hydrological year April 10, 1978 - April 9, 1979, were estimated using a statistically designed catch assessment survey (CAS). The design was based on CAS methods used at Auburn University and incorporated results from a frame survey conducted during the 1977 hydrological year on the Upper Meta River.
Total catch in 1978 was 1,071,366 kilograms from 126,334 Fishing Economic
Unit (FEU)-days where I FEU-day was equivalent to 1.8 fisherman-days. Average
catch per FEU-day was 8.1 kilograms. Ninety-one percent of the catch came
from the main river and upper tributaries (70 percent and 21 percent, respectively).
Similarly, 88 percent of fishing effort (FEU-days) was expended in the main
river and upper tributaries (70 percent and 18 percent, respectively). Catch
and fishing effort in lower tributaries, especially those on the southern
side of the Meta River, were relatively insignificant.
The annual harvest was evenly distributed between the high and low water seasons. However, because the low water season was 71 percent as long as the high water season, daily catch was actually higher during low water. This was due primarily to increased daily fishing effort within the main river stratum during the low water period. Catch per unit effort changed only slightly from the high water season (7.9 kilograms per FEU-day) to the low water season (8.4 kilograms per FEU-day). The relative standard error (RSE) for fishing effort (9.9 percent) indicated that samples were providing relatively precise estimates of this variable on an annual basis. Variation in fishing effort was inherently low because artisanal fishermen live near the river and their frequency of fishing changes little within seasons. Catch estimates were more variable, however, giving a RSE of 25.1 percent for the year; greatest variation was encountered in the low water season (RSE = 44.4 percent). Further seasonal stratification is recommended to reduce variation in catch estimates.
Future catch assessment surveys on the Upper Meta River are outlined and
sampling schedules within time strata are defined. The number of time strata
will be increased from two to four with the addition of one stratum for the
rising and one stratum for the falling water season. It is recommended that
six samples be taken within each time stratum; due to the logistics of sampling,
two or three samples will be taken during a single field trip and trips will
be systematically scheduled. The Upper Meta River will be divided into two
geographical strata, one composed of all tributaries and the other composed
of the main river only. Sample sections will be chosen with nonuniform probability,
with twice as many samples coming from the main river stratum as from the
tributary stratum (four samples and two samples, respectively).
Application of nonuniform probability sampling is recommended for initial
surveys of all river fisheries within Colombia's Orinoco System. A pre-survey
overflight will
provide initial sampling probabilities based on number of canoes counted per
section, and initial time strata will be the same as defined for the Upper
Meta River. Strata definition and sampling probabilities for later surveys
can be amended based on information gathered during the initial survey.
A 1O-year CAS sampling program for Colombia's Orinoco System is proposed.
Sampling will be conducted on the Upper Meta River in alternate years (from
1978), Six other Orinocian rivers will be sampled, one each year, during successive
alternate years beginning in 1979. These other rivers have much less potential
for immediate fisheries development than does the Upper Meta River and thus
merit less sampling effort. After 1989, consolidation of sampling to include
two or more river fisheries in I year may be feasible, thereby allowing completion
of data collection necessary for a Schaefer surplus yield model in all fisheries
of the Colombian Orinoco System within 15-20 years from 1978. Methods for
obtaining estimates of maximum sustainable yield and optimum fishing effort
at the community level based on the Schaefer surplus yield model are discussed.