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PAPUA NEW GUINEA
Yonki fisherfolk: report of a survey among people fishing at Yonki Reservoir, upper Ramu River, Eastern Highlands Province
A report prepared for the Sepik River Fish Stock Enhancement Project, PNG/85/001
by
Peter G.M. van der Heijden (Associate Professional Officer)
FOOD AND AGRICULTURE ORGANISATION OF THE UNITED NATIONS Rome 1993
11
This report was prepared during the course of the project identified on the title page. The conclusions and recommendations given in the report are those considered appropriate at the time of its preparation. They may be modified in the light of further knowledge gained at subsequent stages of the project.
The designations employed and the presentation of the material in this document do not imply the expression of any opinion whatsoever on the part of the United Nations or the Food and Agriculture Organisation of the United Nations concerning the legal or constitutional status of any country, territory or sea area, or concerning the delimitation of frontiers. ill
Acknowledgements
This survey would not have been possible without the permission and support from the Papua New Guinea Electricity Commission (ELCOM). I would especially like to thank Mr. Jack Orere, ELCOM Assistant Environmental Officer based at Yonki, who has been very helpful with organising transport and accommodation and for providing valuable information. I would also like to thank Mr Henry Gumanz who has been responsible for a great number of the interviews conducted along the reservoir, and who has been a very helpful and pleasant companion during many surveys conducted by the author in Papua New Guinea.
For bibliographic purposes this report should be referred to as:
Van der Heijden, P. G. M. 1993. Yonki fisherfolk: report of a survey among people fishing at Yonki Reservoir, Upper Ramu River, Eastern Highlands Province. A report prepared for the Sepik River Fish Stock Enhancement Project. FI:/PNG/85/001 Field Doc. 19. FAO, Rome. 26p.
Keywords:
Papua New Guinea, Socioeconomics, Reservoir, Fisheries, Ramu River Basin, Fisheries Production, Fisheries Yields, Fish Stocking, Fish Introductions iv TABLE OF CONTENTS
1. INTRODUCTION ...... 1
2. METHODS ...... 1
3. RESULTS ...... :...... 6
3. 1. Number of people interviewed; places of residence ...... 6 3. 2. Participation by other members of the household in fishing; estimated fishing frequencies of the respondents ...... 6 3.3. Fishing methods used, duration of the fishing trips ...... 6 3.4. Yield per fishing trip ...... 9 3.5. The composition of the catch ...... 10 3.6. How the fish was used; the sale of fish ...... 15 3.7. Fisheries problems experienced by the respondents ...... 15 3.8. Fish species preferred for consumption ...... 15 3.9. Sources of cash income; average annual income derived from these sources ...... 17 3.10. Consumption of food of animal origin ...... 18 3.11. Number of people fishing and the number of fishing craft...... 19
4. DISCUSSION ...... 19
4.1 Some notes on the accuracy of the data collected ...... 19 4.2 Participation of the various sex/age groups ...... 20 4.3 Dailtfish yield ...... 20 4.4 Yield per hook-hour ...... 20 4.5 Total annual catch from Y onki reservoir...... 21 4.6 The economic status of respondents ...... 22 4.7 The consumption of food of animal origin ...... 22 4.8 Fisheries problems experienced by the respondents ...... 23 4.9 Preferences for fish species ...... 23 4.10 Some concluding remarks about the Y onki reservoir fishery and its future ...... 23
5. REFERENCES ...... 25
ANNEX ...... 26
Length-weight relationships for the fish species ...... 26
FIGURES & TABLES:
Fig. 1. Map of Y onki reservoir ...... 2
Fig. 2. Average weight of fish caught per person per completed fishing trip from the shore with hook & line in Yonki reservoir in 1992 ...... 14 v Fig. 3. Average number of fish caught per person per completed fishing trip from the shore with hook & line in Yonki reservoir in 1992 ...... 14
Table 1. The fish species of which pictures were shown to the respondents, the total length (TL, mm) and corresponding weight (WT, gr) of the various sizes shown on the pictures ...... 4
Table 2: Dates the surveys were conducted, number of men, women, boys and girls interviewed, and economic status of the respondents ...... 7
Table 3: Places of residence of the respondents, and the number of people interviewed from each village or township ...... 8
Table 4. The average number of fishing trips per season and per year of men, women, boys and girls interviewed at Yonki Reservoir ...... 8
Table 5. The percentage of the respondents from each sex/age group that stated to have started fishing only after Yonki Reservoir was made ...... 9
Table 6. The number of unfinished and completed fishing trips from the shore as reported by the respondents, the number of persons involved, the total catch and the yield/fishing person/day ...... 10
Table 7: The total catch of all completed fishing trips, average of the various sex/age groups, the number of persondays and the average yield/person/fishing day for each sex/age• group ...... 11
Table 8. The number of fishing trips (unfinished plus completed) which took place from the shore, the total catch, the total fishing effort in hookhours and the average yield/hookhour at each site ...... 11
Table 9. The number of fishing trips (unfinished plus completed) which took place from the shore during the 5 surveys, the total effort in hookhours, and the average yield/hookhour during each survey ...... 12
Table 10. The number of fishing trips (unfinished plus completed) which took place from the shore, the number of persons involved, the total catch and the average yield/fishing person/day at each site ...... 12
Table 11. The number of completed fishing trips with a raft or canoe, the number of persons participating, the total catch of these trips and the average yield/person/day ...... 13
Table 12. The composition of the catch of the respondents during the surveys (sum of catch of unfinished+ completed trips) ...... 13
Table 13. The use of the fish caught from Yonki reservoir ...... 15 vi Table 14. The percentage of the respondents who stated to have sold some fish in the past...... 15
Table 15. Problems relating to fishing at Yonki Reservoir as reported by the respondents (N = 192) ...... 16
Table 16. Fish species preferred for consumption by people fishing at Yonki Reservoir...... 16
Table 17. Sources of cash income, the number of households having an income from these sources, and the average annual amount per household earned from these sources ...... 17
Table 18. Types of food from animal origin consumed in the 2 days before the interviews took place or during the last meal with food from animal origin if none was eaten during the 2 days before the interview took place ...... 18
Table 19. The number of people found fishing at Yonki Reservoir, the number of bamboo rafts, canoes, fish traps and gill nets counted on three occasions ...... 19
Table 20. Estimate of the total annual yield of Y onki Reservoir ...... 21
Table 21. Average annual yields (kg/ha) from reservoir fisheries of six Asian countries. (from De Silva, 1988) ...... 22 1 1. INTRODUCTION
In January 1991 the dam built for electric power generation at Yonki township in the upper Ramu was closed. This started the flooding of grasslands, gardens and coffee plantations in the Arona Valley. In November 1991 the reservoir, which is at 1260 meters above sea level, reached the Full Supply Level and water started to flow over the spill way. At this level the reservoir covers an area of 2200 hectares. The shoreline of the reservoir is very dendritic and has an approximate length of 50 to 60 km. The new reservoir is the biggest water body in the high altitude region (i.e. > 1000 m above sea level) of the Sepik-Ramu catchment area. According to the 1990 National Population Census 9179 people live in census units within approximately 6 km from the reservoir, of which 2631 live in Yonki Township. Figure 1 shows a map of the reservoir with Y onki township and some of the nearby villages.
The fish already present in the upper regions of the Ramu River successfully colonised the growing lake and before the water reached the spillway level the residents of Y onki township and of the nearby villages had staited to catch fish in the reservoir. Every day people with fishing poles can be seen from the Highlands Highway which crosses the Ramu River at the dam site. To study this interesting increase in fishing activity the Sepik River Fish Stock Enhancement Project approached the Electricity Commission (ELCOM), which manages the lake, and asked for approval and technical support to conduct a number of surveys among the people fishing in the reservoir. The approval and support were given and from February 1992 to December 1992 the development of the fishery at the reservoir was monitored. This report contains the results of the surveys which were conducted durin~ 1992 to monitor the development of the fishery at Yonki. Due to time constraints the analysis has been only brief.
2.METHODS
Five surveys were conducted in 1992 at 2 to 3 months intervals. During one survey between 38 and 45 people were interviewed at 3 or 4 different sites along the shore of the reservoir while they were fishing. In total 201 interviews took place in which 196 people were interviewed. Five persons were interviewed twice. Interviews took place at a total of 6 sites along the reservoir and along the pool below the spillway. These sites are indicated in Figure 1. The interviews were conducted by two male staff members of the Sepik River Fish Stock Enhancement Project. One of the staff members was a national Department of Fisheries & Marine Resources technician (Henry Gumanz) and the other was an FAQ staff member (Van der Heijden). A survey form developed by the Sepik River Fish Stock Enhancement Project (SRFSEP) for surveys in the Sepik-Ramu catchment area was used, sample forms are provided in Van der Heijden (1993a). The interviews were conducted in PNG Pidgin English. At the start of each interview the date, place and time were recorded. Questions asked were relating to the following topics:
- Name, sex, religion, place of residence, marital and economic status of the respondent (i.e. wage earner; lives in village from farming, hunting and fishing, student; owns a business/store; etc) - Number of members in the household of the respondent, sex and age of any other fishing household member. - Approximate fishing frequency of the respondent during the rainy 2 Fig. 1. Map of Yonki reservoir
Scale: approximately 1:55,000
_ ... -..:to Lae ,,,. .,...... ,,,. ,,,. - ,,,.
... ""~Swiss N ... .,. .,. .,. •. Mission t
...... ·.. .• • .. .. . Anasina •••• ...... *···· .. .. lo ...... 3 .::..:;.bonamo Kainantu • ~\ \ \ \ \ \ "' . \ ... _,,,. "' YONKI .
RESERVOIR 4. Pundibasa :'*...... * • .· .• ...... • .• .. • ...... *-.' •• Bioka •• •• •. • to :I Aiyura
------Highlands highway
• • .. • • • • .. * • • • • • Gravel road
7 Interview sites
-f;r: Village 3 and during the dry season. - If fishing was practised before Y onki Reservoir was created. - Dates, place, and estimated duration of the most recent 1 to 4 fishing trips at Y onki Reservoir. - Methods used to catch fish during the most recent fishing trips at the reservoir; the number of hooks used during each reported fishing trip if the fish was caught with hook & line; if the fishing took place from the shore or from a bamboo raft, canoe or boat. - Estimated catch of each reported trip: species caught, number and sizes of each species caught. - The number of people who were involved in catching the fish during the most recent fishing trips. - How the fish was used (i.e. eaten by the household members, donated, sold, etc) - If the respondent ever sold fish caught from Y onki Reservoir, or if he/she or any other household member ever bought fresh or smoked fish caught from Yonki Reservoir or elsewhere. - Problems experienced that are related to fishing at Y onki reservoir. - Which fish species was preferred for consumption. - Types of food from animal origin eaten during the 2 days before the interview took place, or during the last meal with animal protein if no food from animal origin was eaten during the 2 days before the interview. - Sources of cash income of the household of the respondent, and •estimated amount of cash obtained per year from each source.
Question 8 (dealing with sources of cash income on the individual survey form, Van der Heijden l 993a) was only asked during the last 2 surveys (October and December 1992). The fish species caught by the respondents on the day the interview took place were recorded, including their numbers and sizes. The fish caught by the respondents during their most recent fishing trips were identified by showing the respondents coloured pictures of the fish species commonly caught in Yonki Reservoir (see also Van der Heijden 1993a). From each species 4 or 5 different sizes were shown, and the respondent could indicate the size of the fish caught during the most recent fishing trips by comparing them with the size of the fish on the pictures shown. For example: a person could point at the pictures of the common carp and say that she caught 2 carps of size 2 and 1 carp of size 3 the day before yesterday. The weight of the fish with the same size as the ones shown on the pictures was estimated with length-weight equations which were derived from the numerous measurements and weighings of fish done by the SRFSEP in the past. The length-weight relationships of the fish species commonly caught at Yonki Reservoir are listed in the Annex. The fish species of which pictures were shown to the respondents, the total length (TL, mm) of the different sizes of fish shown, and the estimated total weight (WT, gr) of fish with these lengths are listed in Table 1.
During the first survey the number of hooks used was only recorded from 14 out of 39 people interviewed. One survey took 2 to 3 days to complete. 4 Table 1. The fish species of which pictures were shown to the respondents, the total length (TL, mm) and corresponding weight (WT, gr) of the various sizes shown on the pictures.
s12eciel2 ITL WTITL WTI TL WTI TL WTI TL WT! TL TW Common carp 180 8 I llO 241170 651220 1821310 5151390 1038 (C~12rinys car12io) I I I I I I I I I I I I Tilapia, makau 170 51100 19 1130 421190 ll5 I 265 3351 (Oreochromil::l mos- I I I I I I sambicys) I I I I I I I I I I I I Redbreast tilapia 170 81100 211130 401180 ll41270 3191 (Tilagia ~endalli) I I I I I I
In general the rainy months in the Yonki area were reported to be from December to May, and the dry months are from June to November. For computation of the average yearly fishing frequency, a rainy season lasting six months and a dry season of the same length was assumed.
If the frequency of the most recent fishing trips (called actual fishing frequency) was not in line with the stated fishing frequency for the season during which the interview took~· place then the average of the stated and actual frequency was used to compute the estimated fishing frequency for that season. For example: if an interviewee stated to fish three to four times per week during the rainy season, but she actually went only 3 times during the past 3 weeks, and the interview was conducted during the rainy months, then the average freqtiency of 2.25 times/week was used to compute the fishing frequency during the rainy season. No similar correction was made on the stated fishing frequency during the dry season for this respondent. If a respondent stated to have fished "the whole day", it was assumed that he/she fished for 9 hours. If he/she stated to have fished only "a half day" then it was assumed that the fishing was done during 4.5 hours. The fishing which was done at the moment of the interview is called an unfinished fishing trip, and the reported trips which took place before the day of the .interview are called finished or completed trips.
Answers like "once a week" or "twice a week" were often received at the question about the frequency with which food crops were brought to the market for sale. To compute the annual income from this source it was assumed that marketing took place during 35 weeks per year, allowing 17 weeks during which the gardens did not yield enough to make the trip to the market worthwhile. So marketing was supposed to have taken place 35 or 70 times when the respondent answered "once a week" or "twice a week" respectively. The income from one day at the market was estimated by averaging the income from a day with good sales and the income from a day with bad sales at the market as stated by the respondent.
Distance between the house and the fishing site was always expressed in minutes or hours walking. To compute the distance covered a walking speed of 5 km per hour was assumed. The respondents were grouped in 4 groups according to their age and sex. Men 5 and women are defined as males resp. females who are 16 years of age or older, and boys and girls are defined as males resp. females who are 15 years of age or younger.- The data collected during the interviews were entered into a computer data base (Programme: Lotus-123). For each survey a separate file was made. Data were entered under the same column headings as used for the surveys conducted in various villages within the Sepik-Ramu catchment area as far as these were also applicable for the Yonki surveys. The column headings and the way the data are entered and processed are described in detail in van der Heijden (1993a). For the Yonki surveys the following extra columns were added:
- "NoGearUsed" in which the number of hooks used during the reported trip was recorded.
- "Effort" in which the total fishing effort in hookhours of the trip was recorded. The value entered in this column is equal to the value entered under "Duration" x the value entered under "Eff01t". When the reported catch was the combined catch of the respondent plus one or more other persons than one the effort of the other person(s) is added to the effort of the respondent.
- "Fished before?", under which the answer to the question whether the respondent also fished before Yonki reservoir was created is entered (Yes or No).
- "Raft/canoe?", under which a yes is entered when a raft or canoe ..was used to reach the fishing site, and nothing was entered when fishing was done from the shore.
The total fishing effort for a fishing trip was expressed in hookhours and computed by multiplying the duration of the trip (in hours) with the number of hooks used during the trip. A hookhour is defined as an hour of fishing with one hook. For example, if a respondent reported the result of a trip which lasted a half day (= 4.5 hours) and she fished with 3 hooks, than a value of 13.5 is entered under "Effort". If she was accompanied by one child who fished with one hook and the reported catch was the combined catch of both, then a value of 18 was entered under "Effort".
On 3 occasions the number of people fishing on the shore or from a canoe or raft were counted while riding a boat parallel to the shoreline of the reservoir. The sex and whether the person seen fishing was an adult or a child was also recorded. The number of rafts and canoes used for fishing or parked at the shoreline, and the number of stationary fishing gear seen (i.e gillnets and fence traps) were also recorded. Two counts were done during weekdays, and one was done during a weekend. It took approximately 4 to 5 hours to complete a boat ride around the whole lake parallel to the shore. Counting took place in the late morning and in the afternoon. 6 3. RESULTS
Copies of the raw data are contained in Van der Heijden (1993a).
3. 1. Number of people interviewed; places of residence
Table 2 shows the dates the interviews took place, the number of interviews conducted during each survey, the number of people in each sex/age group, the economic status of the interviewees of each survey. Table 3 lists the names of the villages where the respondents were residing, and the number of people from each village that were interviewed. Respondents from Keketuantu, Uminufintenu, lsontenu, Barola, Kainantu, Agarabi, Barapa, Kainua, Keyae, Tumar, and Isomfa (which are at a distance of 8 to 25 km from the reservoir) all came by car (private or public transport) to the reservoir. Practically all the other respondents walked to the fishing site. People stated to have walked a distance between 20 meters and 10 km from their house to the fishing site, with an average distance of 2 to 3 km for the respondents who could give an estimate of the time spend to reach the site.
3. 2. Participation by other members of the household in fishing; estimated fishing frequencies of the respondents
The respondents belonged to 181 households with a total number of 1020 members (average: 5.64 members/household). In these households 496 members (48.6%) are reported to fish at least once a year, mostly at Yonki Reservoir. The sex/age composition of these fishing b.ousehold members was as follows:
Men: 42.3% Women: 19.2% Boys: 28.4% Girls: 10.1 %
The average fishing frequency of the 181 respondents (excluding those who were fishing for the first, second or third time during the interview) was 130.6 times year. If the 16 respondents who fished for the first, second or third time are included the average fishing frequency of all respondents was 120.1 times per year. The average fishing frequency of the various sex/age groups is listed in Table 4. This table does not include the respondents who fished for the first, second or third time.
Of the 17 4 respondents who answered the question whether they fished before Y onki Reservoir was created 47.1 % stated that they started fishing only after the reservoir was established. There is remarkable difference in the answers between the sexes: 76.5% of the female respondents and 40.0% of the male respondents took up fishing only after the reservoir was made (Table 5).
3.3. Fishing methods used, duration of the fishing trips
During 99.0 % of the 572 fishing trips reported by the respondents only bamboo fishing poles with lines and hooks were used. The poles were 2 to 4 min length. On average 2.6 poles were used per respondent. The hooks were baited with either a worm, a piece of boiled sweet potato or a piece of home-baked fritter (flour ball). A bamboo raft or canoe 7 was used on 22 occasions(= 3.8% of the total number of reported fishing trips) to transport the respondents to a fishing site away from the shore.
Table 2: Dates the surveys were conducted, number of men, women, boys and girls interviewed, and economic status of the respondents.
I 1992 I IFebr May July Octo Dec em I Res12ond!ilnts 123-25 7-9 2~~30 7-10 19-23 I Total I % . I I I Number of men I 32 24 28 21 24 I 129 I 64.0 I I I Number of women I 3 6 6 10 5 I 30 I 14.9 I I I Number Of boys I 4 7 4 8 14 I 37 I 18.4 I I I Number of girls I 0 1 0 2 2 I 5 I 2.5 I I I Total I 39 38 38 41 45 I 201 1100.0 I I l I Stap long ples* I 18 25 30 34 27 I 134 I I Wage earners: I 0 7 3 5 3 I 18 I I Business/store I 1 0 0 0 0 I 1 I I Student I 2 4 1 2 14 I 23 I I PMV owners/dravers\ 3 0 1 0 0 I 4 I I Status unknown I 16 2 2 0 1 I 21
* "Stap long ples" is the PNG Pidgin description of a person who lives in a village, has no income from wages or a business, does not attend school and lives mainly from subsistence agriculture, hunting, fishing, and sales of some food and/or cash crops. 8 Table 3: Places of residence of the respondents, and the number of people interviewed from each village or township
Number of Nfillle village/townshig :i;:es12ondents Abonamo 17 Kainua 2 Agamura: 2 Kainantu 1 Agarabi 3 Kaporei 3 Akay Plantation 1 Kassam 13 Aki pa 4 Kasempa 2 Anasina 20 Keketuantu 17 Arona 1 7 Keyae 1 Arona 2 1 Kolwar a 1 Barapa 1 Korean Camp 2 Baro la 1 Marnarai 4 Batakona 1 Noandava 1 Bioka 5 Okentenu: 2 Bona fa 1 Pundibasa 1 1 Driller's Camp 1 Pundibasa 3: 23 Goroka Block 5 Simera: 2 Isomfa 3 uminufintenu: 11 Isontenu 3 Wopepa 1 Puri 5 Yauna 9 Tumar 1 Yonki township 17
Table 4. The average number offishing trips per season and per year of men, women, boys and girls iijterviewed at Yonki Reservoir.
Sex/age I I Average number of fishing days grou:g I Numl;;2er I Rg,in;;..:: season I Dr;;..:: season I Year I I I I Men I 63 I 78.3 I 62.3 1140.7 I I I I Women I 18 I 66.0 I 79.2 1145.2 I I I I Boys I 23 I 65.6 I 60.5 1126.0 I I I I Girls I 4 I 39.3 I 65.0 1104.3 I I I I All I 108 I 72.1 I 64.9 1136. 9 9 Table 5. The percentage of the respondents from each sex/age group that stated to have started fishing only after Yonki Reservoir was made.
Men Women Bovs Girls All
37.7 75.9 47.1 80.0 47.1
Total number of_responents that answered this question: 1106 29 34 5 174
The average amount of money spent on hooks and fishing line was K 0.98/respondent, and ranged from nil to K2.50. Lines and hooks were bought from stores at Yonki, Kassam Mission, Kainantu and Lae.
During 2 reported trips only bare hands were used to catch fish in a shallow bay of the lake after the water was made muddy to force the fish to come to the surface. During 2 reported trips bow and arrows were used to shoot fish. During 2 reported trips a lady used a fine-meshed handnet to catch the small (30 to 40 mm long) mosquito fish (Gambusia affinis) in a shallow part of the reservoir. Only one respondent reported also to have used a borrowed gill net on several occasions in the past, but the results from the days he used this gear were not recorded since they happened too long ago.
The respondents spent on average 6 hours fishing during one fishing day.
3.4. Yield per fflihing trip
Table 6 shows the number of completed and the number of unfinished fishing trips which took place from the shore line, the number of persons who were contributing to the total reported catch, the total catch for all these trips, and the average yield/person per fishing trip for the 5 surveys. The average yield/person/fishing day for the various sex/age groups was computed from all the total catch of all completed fishing trips (including fishing from a raft or canoe and with all methods). The average yield/person/fishing day is given in Table 7. Table 8 shows the number of fishing trips that were reported to have taken place at the 7 sites along the reservoir where the interviews were conducted (see Figure 1) in each survey, the total fishing effort (hookhours) at each site, the total catch of the trips at each site, and the average yield/hookhour at each site for each interview. Table 9 shows the number of fishing trips, the total fishing effort, the total catch and the average yield/hookhour for each survey. Table 10 shows the number of fishing trips, the total fishing effort, the total catch and the average yield/hookhour for each site where the respondents reported to have fished. The average yield/hookhour for all fishing trips (finished+ unfinished) with hook and line from the shore was 31.2 gr.
During the surveys of May, July and October some respondents reported the results of trips during which a raft or canoe was used to reach the desired fishing spot. During several of these trips the number of fish caught was too high for the respondents to be able to give an accurate estimate. Instead the quantity was expressed as "a sauce pan full", a "lOkg rice bag half full", and "a bucket full". These quantities were assumed to weigh 1.0 10 kg, 4.0 kg and 7.0 kg respectively. The results of these trips during which a raft or canoe was used are summarised in Table 11.
Table 6. The number of unfinished and completed fishing trips from the shore as reported by the respondents, the number of persons involved, the total catch and the yield/fishing person/day.
F!iib:!Z Ma:t::n Jul9Z Q~t;9Z Q!ilC22 :rotg,l Unfinished triQs: 39 28 39 38 45 189 number of persondays 42 33 39 48 52 214 Total catch (gr} 4186 4620 3779 8320 8464 29369 Yield/pers/day(gr} 100 140 97 156 163 137
COlllQleted triQS: 82 62 73 76 . 68 361 Number of persondays 82 67 73 86 70 378 Total catch (gr} 30757 28504 28724 45585 26878 160448 Yield/pers/day (gr} 375 425 393 53 0 384 424
The average catch/person/fishing day of the 2 trips during which only bare hand were used to catch the fish was 1860 gr. The average catch/person/fishing day of the 2 trips during which bow and arrows were used was 182 grams. The average catch/person/fishing day for the 2 trips during which a handnet was used to catch mosquito fish was estimated at 1 kg.
3.5. The composition of the catch
Only two fish species were reported to be caught during the surveys of February and May 1992. These species are the common carp (Cyprinus carpio) and the Mozambique tilapia (Oreochromis mossambicus). In the survey of July 1992 a third species appeared: the redbreasted tilapia (Tilapia rendalli). This species was introduced in the Upper Ramu area by the Sepik River Fish Stock Enhancement Project in the second half of 1991. In September and October 1992 an additional 28000 redbreast tilapia fingerlings were stocked at Yonki Reservoir by the SRFSEP. Table 12 shows the catch composition of the total observed and reported catch of all the unfinished and completed trips of the 5 surveys. The trips of which the respondents could not give an estimate of the number except from descriptions like "a 10 kg rice bag half full" or "a bucket full" are left out from the estimated number of fish caught.
Figure 2 shows the average yield/person/completed fishing trips, and the contribution of the various species to the weight of the catch. Figure 3 shows the average number of fish caught per person per completed trip and the contribution of each species to the average number of fish caught per trip. 11 Table 7: The total catch of all completed .fishing trips, the average of the various sex/age groups, the number of persondays and the average yield/person/fishing day for each sex/age group.
Total Total number Average yield/ Se:i:;;Lg,ge m:o!JQ CatQb (g;i;;:l Qs:l:t:§lOOQQ.;LS Q!,ilrsonLs:lia:L (gr) Men 150983 237 637 .1 Women 28774 60 479.6 Boys 28661 71 403. 7 Girls 1436 14 102.6
Table 8. The number offishing trips (unfinished plus completed) which took place from the shore at the sites indicated on Figure 1, the total catch, the total.fishing effort in hookhours and the average yield/hookhour at each site.
Total Number Total Effort Yield/ Site Montb repo;i;;:ts catch.gr (bookbours) bookbour.gr
1 May 29 16294 234.5 69.5 Oct 47 24584 525.5 46.8
2 Feb 9 3923 78 50.3 Jul 32 11714 307 38.2 Dec 27 3120 196 15.9
3 • Feb 9 3076 89 34.6 Jul 43 8541 449 19.0 Dec 35 9160 308.25 29.7
4 May 24 3950 224.5 17.6 Oct 31 16562 321 51. 6
5 Oct 21 5403 444 12.2
6 Feb 12 1559 132 11. 8 Jul 38 13112 594 22.1 Dec 51 23062 1064 21. 7
7 May 37 17973 316.75 56.7 Oct 13 6639 120 55.3
Total: 458 168672 5403.5 553.0 Average: 34.6 StanDev: 17.8 12 Table 9. The number offishing trips (unfinished plus completed) which took place from the shore during the 5 surveys, the total effort in hookhours, and the average yield/hookhour during each survey.
Survey Number Total Total Yield/ Month of reports catch lgrl Effort hookhour
February 30 8558 299 28.6
May 90 38217 775. 75 49.3
July 113 333 67 1350 24.7
October 112 53188 1410.5 37.7
December 113 35342 1568.25 22.5
Total 458 168672 5403.5
Average 32.6
Standard Deviation: 18.l
Table 10. The number offishing trips (unfinished plus completed) which took place from the shore at the sites indicated on Figure 1, the number of persons involved, the total catch and the average yield/fishing person/day at each site.
• !Number !Total \Total number! Yield/ Sitelof trips!Catch.grJof hookhoursl hookhour (gr)
1 76 40878 760 54
2 68 18757 581 32
3 87 20777 846.25 25
4 55 20512 545.5 38
5 21 5403 444 38
6 1101 37733 11790 21 I I 7 I 50 24612 I 436.75 78 I I Total 1458 168672 15403.5 286 Average I I 40.9 StanDeviatl I 18.l 13 Table 11. The number of completed fishing trips with a raft or canoe, the number of persons participating, the total catch of these trips and the average yield/person/day.
IMa:l '92 JUl:i '92 Oct '92 Tots:i,1 Number of trips I 9 4 9 22 Number of persons I 12 4 11 27 Total effort,hookhoursl249 57 240.5 546.5 Total catch (kg) I 33.939 3.938 18.754 56.631 Yield/person/day (kg) I 2.828 0.985 1. 705 2.097 Yield/hookhour (gr) 1136 69 78 103. 6
Table 12. The composition of the catch of the respondents during the surveys (sum of catch of unfinished+ completed trips).
SQe~iSlS Feb92 Mg,y92 Jul92 Oct92 Dec92 Total c.car12io number 370 314 232 315 248 1479 % of total number 83.7 43.5 38.7 21. 4 17.4
O.mossgmbic]Js number 72 408 675 513 1668 % of total number 16.3 56.5 45.8 36.0
T.rendalli number • 0 0 483 664 1147 % of total number 0 0 32.8 46.6
O.mossambicus + 368 368 T. rendalli 61.3
Total number 442 722 600 1473 1425 4662 14 Fig. 2. Average weight of fish caught per person per completed fishing trip from the shore with hook & line in Y onki reservoir in 1992.
H tn
~ 0 {{) 600 H w Pi "Pi 500 ·rl H j.) 400 'I) ·· .. ·<::::::::::::::::::·""' w j.) "·~ w 300 rl Pi 8 0 200 ~/ / ..... u ! / / l/// /// "'I) rl 100 (//' w (,:/ ·rl ( ~
w 0 --'-"~+-''--'--""-~'""'--''--'i-_._'-'-~""'--<--J--+--'-"-""----'--'--''-+-"--''-'-~-'-'-_._,__..._,_, tn Feb Ma.y Ju.l Oct:: Dec ~ Su.r-'..Teoy (m=n.th) ~ V..Zl c . c a.r-pi = L~: ... :·:.;: o . me:> .s s a..rnb i cu. .s ~ T .. i-en c_---3_a_ l l i > ~
Fig. 3. Average number of fish caught per person per completed fishing trip from the shore with hook & line in Y onki reservoir in 1992.
13
12
11
10
9
8 . " .. ··.. ·.'
7 ;.... ·····... :::~~.·...... :"··.. l
6 ;-... ::::::~:··..... : s !::::::<.. ::·<:::::::::::.·.:.:.:.:·'..: ... ".".".".".·.:! t~ . "·· ... ···.... 2~ ~/ ?7~' ~ ~ :~-1/.c ~ l@A-Y~ Febr-u.a.r-y Ma.y Ju.l Oct Dec
Su.r-'-Tey (m=n.th) VZ.I C .. ca.rpic:> 1.':::·:..":·:·:·~ o.rnc:>ssa.rnb:Lcu.s ~ T .. ren..da..lli 15 3.6. How the fish was used; the sale of fish
Table 13 summarises the answers to the questions related to the use of the fish that were caught during the reported fishing trips. One respondent who had not yet caught any fish on the day the interview took place said that he planned to take the fish alive to the creeks near his village (Pundibasa 1 ), and release them to boost the fish stock in these streams. These creeks are within the Markham catchment area.
Table 14 shows the number of respondents who reported to have sold some fish caught at the reservoir in the past.
Table 13. The use of the fish caught from Y onki Reservoir
Number Percentage Fish consumed by the respondent and his/her household: 2739 88.0
Donated to people from the same village as respondent: 298 9.6
Stocked in fish pond: 32 1. 0
Donated to people from outside the village: 2 0.1
Fish sold: 42 1. 3
Total: 3113 100.0
Table 14. The percentage of the respondents who stated to have sold somefzsh in the past.
survey I Feb Ma:,:: Jul Oct Dec Total Number of respondents from I whom an answer was recorded: I 30 35 37 39 42 183 Percentage of respondents I that sold fish: I 3.3 11. 4 13. 5 17.9 16.7 13 .1
3.7. Fisheries problems experienced by the respondents
Table 15 shows the number of respondents in each survey who stated to have the problems mentioned that are related to fishing at Yonki Reservoir.
3.8. Fish species preferred for consumption
Table 16 summarises the answers given by the respondents to the question about fish species preferred for consumption. Respondents who mentioned more than 2 species were grouped together with the respondents who indicated to have no clear preference. 16 Table 15. Problems relating to fishing at Yonki Reservoir as reported by the respondents (N =192).
Mentioned by % of the Problem Number respondents No Problems: 25 13. 0
Seasonal problems: 114 59.4
Distance to the lake too far: 60 31.3
The fish are too small: 48 25.0
There is not enough fish: 24 12.5 overfishing is taking place: 7 3.6
Can not fish far from shore: 1 0.5
Sometimes no fish caught: 13 6.8
Respondent has not enough fishing gear: 5 2.6
Not enough carp in the lake: 2 1. 0
Now catch is smaller than last year: 1 0.5
Favorite fishing spot too far to reach: 1 0.5
Big fish sometimes breaks line, takes hook: 1 0.5
Water is too turbid to use speargun: 1 0.5
Hooks lost on tree trunks: 1 0.5
Redbreast tilapia ate and chased carp and Mozambique tilapia: 3 1. 6
Table 16. Fish species preferred for consumption by people fishing at Yonki Reservoir.
Prefered by Species number of respondents Percentage carp Cyprinus carpio 80 57.9 Tilapia Oreochromis mossambicus 16 11. 6 Redbreast tilapia Tilapia rendalli 19 13. 8 Eels (Anguilla sp) 11 8.0 Trout (Onchorynchus mitschii) 1 0.7 Carp + redbreasted tilapia 2 1. 4 No clear preference: 9 6.5 17 3.9. Sources of cash income; average annual income derived from these sources
Table 17 lists the sources of cash income mentioned by the respondents in the surveys of October and December, the percentage of the households which derive part of their total cash income from this source, and the average level of income derived from this source by the households that have an income from this source. As can be observed from this table ownership of a Public Motor Vehicle (PMV), a store or. other business, or a having a job all make up a big proportion of the total annual income of the households who do have these sources of cash income. However, 70.1 % of the respondents report not to have any of theseincome sources. Their cash income comes predominantly from selling food crops, coffee and fruit at the nearby markets, and the annual income of these households is estimated to be K 448. 87 , being the average total annual income of 54 households.
Table 17. Sources of cash income, the number househoUls having an income from these sources, and the average annual amount per househoUI earned from these sources.
Number of households Average annual income Source of income with this income source from this source
Marketing garden crops 56 K 342.76
Growing and selling coffee 54 164.92
Wages 16 2716.54
Selling pigs 9 165.63
Remittances from relatives: 9 69.00
Gold panning and selling: 2 8.00
Store ownership: 6 2312.50
Received customary payments: 1 300.00
No regular source of income: 3 ?
PMV ownership 4 7200.00
Fish sales: 7 34.53
Owning a private bar: 1 ?
Selling second-hand clothes: 2 2362.50
Growing and selling chickens: 1 5818.75
Buying and selling chickens: 1 450.00
Total annual household income 76 1354.94 18 3.10. Consumption of food from animal origin
Table 18 shows the type of food from animal origin eaten by the respondents in the 2 days before the interview took place, or during the last meal they had with some food from animal origin when this type of food was not eaten during the 2 days before the interview.
Table 18. Types offood from animal origin consumed in the 2 days before the interviews took place or during the last meal with food from animal origin if no such was eaten during the 2 days before the interview took place. (N:: 201).
Respondents eating this type of food Yesterday 2 days ago Last time Type of food Number % Number % Number %
No food from animals 70 34.8 85 51.2
Tinned meat 6 3.0 5 2.5 1 2.2
Tinned fish 26 12.9 22 10.9 8 17.8
Fresh fish (caught) 51 25.4 30 14.9 17 37.8
Fresh/smoked fish (bought) 1 0.5 0 0 0 0
Pig 11 5.5 11 5.5 5 11.1
Chicken 8 4.0 3 1. 5 0 0
Bandicoot 1 0.5 0 0 0 0
Lamb flaps 26 12.9 27 13 .4 8 17.8
Beef 2 1. 0 3 1. 5 0 0 cuscus 0 0 0 0 2
Can't remember 4 8.9
45 respondents did not eat any food from animal origin in the 2 days before the interview. The 41 respondents who could remember when they had eaten this food for the last time had eaten this type of food on average 5.3 days ago. 19 3.11. Number of people fishing and the number of fishing craft
Table 19 shows the number of men, women, boys and girls counted while fishing at Yonki Reservoir and the number of vessels seen while riding in a boat parallel to the shore on three different occasions.
Table 19. The number ofpeople found fishing at Yonki Reservoir, the number of bamboo rafts, canoes, fish traps and gill nets counted on three occasions. The number ofpersons fishing on May 7 is the sum ofthepeoplefzshingfrom the shore andfrom rafts and canoes.
!Total Dg,te of count-> Ma~ 7, ·n Oct; ~Hd.O I' 92 Qec 22, '221 Li::at:t+sborel Fishing from shore: !Number % Men 99 96 254 I 538 45.6 Women 39 60 137 I 239 20.3 Boys 22 55 169 I 271 23.0 Girls 7 30 92 I 131 11.1 sex/age not sure: _li _2_Q_ _u 1-4..4. Total: 178 261 665 11223
Fishing from raft or canoe: Men 6 53 Women 1 2 Boys 1 24 Girls 1 1 sex/age not sure: __Q __Q Total: 9 80
Total number fishing: 178 270 745
Number of bamboo rafts: 44 69 125
Number of canoes: 26 21 38
number of private boats: 1 0
Number of fish traps: 1 2 ?
Number of gill nets: 0 1 ?
4. DISCUSSION
4.1 Some notes on the accuracy of the data collected
Most of the data collected relied on the memory of the respondents. Many of them did not have (much) formal education, which may have affected the accuracy of the report. This may have been the case especially when larger numbers of fish had to be estimated, or when the date of a past fishing trip or the last time some food of animal origin had to be recalled. However, the majority of the respondents were very cooperative during the interviews and did their best to give an exact answer. 20 Comparison of the percentages of the various sex/age group in Table 2 with Table 19 shows that women and especially girls are under-represented in the group of people interviewed.
It should also be kept in mind that the respondents form a selected group of the population living in Arona Valley and surrounding villages because of the fact that they were interviewed while they were fishing. It is likely that the people who fish more often than the rest of the population have been interviewed.
4.2 Participation of the various sex/age groups
The composition of the group of fishing household members as repmted by the respondents is very similar to the composition of the fishing population at Y onki as recorded during the countings (Table 19). The composition is different from the composition of fishing population in most high altitude villages of the Sepik-Ramu catchment area due to the high percentage of females fishing at Y onki (31 % ). Elsewhere in the high altitude villages fishing takes place mainly in creeks and rivers and 97% of the fishing residents in the villages surveyed were males (Van der Heijden 1993b). Near Lake I viva however women plus girls made up 45.7% of the fishing population. It seems that the nearness of a lake which has other fish species than only eel (as was the case in lake Iviva before the stocking of common carp) stimulates women in high altitude areas to take up fishing, as is confirmed by the high percentage of female respondents (7 6.5%) who started fishing only after Yonki Reservoir was created. It is suggested that women fish more in lakes than in rivers and creeks at high altitudes because the chance of returning home with at least some fish are higher when fishing takes place in lakes.
4.3 Daily fish yield
The average daily yield/fishing person at Y onki is lower than the average daily yield/fishing person at Lake I viva (Enga Province), where an average daily yield of 740 grams was found (van der Heijden, 1993b). Lake Iviva was stocked 30 years ago with common carp. The average daily yield/fishing person at Yonki is higher than the daily yield/person fishing in high altitude streams and rivers with hook & line elsewhere in the Central Highlands. Van der Heijden (1993b) estimated that on average between 100 and 250 grams/person/day were caught with hook & line in some of the high altitude areas of the Sepik-Ramu. This was the case when people stayed near the hook and tried to hook the fish when they saw that the bait had been taken. Fishing with hooks for eels (with the hooks set overnight and checked the next day) may give higher yields when big eels are caught.
4.4 Yield per hook-hour
The average yield of 31. 2 gr/hookhour as reported in section 2.4 is lower than the estimated 72.2 grams/hookhour caught by residents in the Kandep Lakes, Enga Province (Wright 1980). The value found for Yonki is very close to the value found for Lake !viva. Van der Heijden ( 1993-b) estimated an average fish yield of 37 .1 gr/hookhour for this lake and differences in effort may partly explain differences in yields between Y onki and Lake I viva. 21 The average yield/hookhour (Table 9) and the average daily yield/person (Figure 2 and Figure 3) did not show a clear increase or decrease over the year. This is surprising considering the young age of the reservoir, and its fish stock, and the rapid changes of the species composition of the stock due to the entry of T. rendalli into the fishery (Figure 2 and 3). It would be interesting to see if the average yield/hookhour and per person in 1993 increases due to the growth of the numerous young redbreasted tilapia which were present at the end of 1992.
4.5 Total annual catch from Yonki reservoir
With the estimate for the average number of people fishing during a day at Yonki, the estimated sex/age composition of the fishing population, and the average daily yield of men, women, boys and girls it is possible to estimate the total annual catch from Y onki Reservoir for 1992. This is done by multiplying the number of people from a certain sex/age group found fishing during a day (from counts by boat) with the average daily yield/person for that age group, x 365. This gives the total annual catch by this sex/age group. The total annual yield from the reservoir is estimated as the summation of the total annual yield of the 4 sex/age groups. The average number of fishing persons from the 3 counts at the reservoir (Table 19) is 398. However, the number counted in December was exceptionally high, probably due to the holidays and the perceived favourable fishing conditions. It was a day after a night of heavy rain, which is said to give good results because the fish moves to the shore to eat the animals and other edible material washed from the shore. The average number of people counted in May and October was 224. Taking these 2 numbers (398 and 224) as a high and low estimate of the average number of people fishing at the reservoir on a single day a high and low estimate of the total annual yield of Yonki Reservoir is made in Table 20. The current estimated total yield of 40 to 71 tons/year is equivalent to 18 to 32 kg/ha/year. This can be considered a low yield if compared with reservoirs elsewhere in Asia. The average annual yields/ha for reservoir fisheries in Asia, from De Silva (1988), is provided in Table 21. In most countries fishing in reservoirs is done mainly with gill nets. In most Asian countries reservoir fisheries are important and they can be very productive. For example, reservoir fishe1ies in the People's Republic of China depend on continued stocking with several Chinese carp species, and the total annual amount harvested was estimated at 206,434 tonnes in 1985 (Sifa 1988).
Table 20. Estimate of the total annual yield of Yonki Reservoir.
High estimate: !Low estimate: Total I I !Total % of fishing Average Number !Annual !Number !Annual SexLg,ge ,go,g:ylg.tion dail;L :Lield! fishing I Yield, kg lfishinglYield, I I Men 45.6 % 637 gr I 181 42,083 I 102 23,715 I I Women 20.3 % 480 gr I 81 14,191 I 45 7,884 I I Boys 23.0 % 404 gr I 92 13 f 566 I 52 7,668 I I Girls 11.1 % 103 gr I 44 1,654 I 25 940 I I Total: I 71,494 kg I 40,207 22
Table 21. Average annual yields (kg/ha) from reservoir fisheries of six Asian countries. (from De Silva, 1988).
Average Average Country Yield(kq/ha) Range Country Yield (kg/ha)
India 20 (5-100) Bangladesh 46
Indonesia 177 (22-353) I Thailand 47 I People's Rep. I of China 150 (75-675) I I Sri Lanka 283 (84-650) I
The fish stock in Yonki Reservoir is probably still building up and the local community may still be increasing their involvement in fishing. A balance between the species and between production and harvest had probably not been established at the end of 1992. This, plus the low fishing pressure (between 3492 and 6210 hookhours/day, plus 1 or 2 gillnets and traps) explains the low annual yield. With 90% of the fishing taking place from the shore it can be computed that the fishing pressure along the shore is equivalent to 10 to 18 hooks/km shoreline, with an average fishing time of 6 hours. This can be considered as a low fishing pressure.
4.6 The economic status of respondents
The average annual income/household of the Yonki respondents (Kl354.94) is higher than found during surveys in other high altitude villages within the Sepik-Ramu. Van der Heijden (1993b) reported an average annual income of K586.06/household based on interviews with respondents from 197 households from 8 villages. This higher income is caused by a higher percentage of wage earners among the Y onki respondents who were interviewed about their sources of income (21.1 % vs 8.1 % ), the higher income from wages (K2716.54 vs K689.75), the higher percentage of PMV owners (5.3% vs 1.8%), and the high estimated income of the people with a chicken or second hand clothes business. However, the income level of the majority of the households which rely on the sale of food crops and coffee as the main sources of cash income is almost the same as the average household income excluding PMV ownership in 7 villages in the Central Highlands (K448.87 vs K478.80).
4.7 The consumption of food of animal origin
Table 18 shows that fish caught at Y onki has become the most frequently consumed type of animal protein in the households of the respondents. Of all the reported meals with some kind of food from animal origin 36.6% was with fresh fish from the reservoir. In comparison, this was only the case in 6.6% of the 257 meals with food from animal origin reported by 185 respondents from 7 high altitude villages in the Sepik-Ramu catchment area which were not situated near a lake or reservoir (Van der Heijden 1993b). The contribution of imported sources of animal protein (tinned meat, tinned fish and lambflaps) to the total number of meals with animal protein was 47.7% for the Yonki respondents and 23 58% for the 185 respondents from high altitude villages not near to a lake. Of the 185 respondents from high altitude villages not near to a lake 22.2% had not eaten any food from animal origin in the 2 days before the interview took place. They had eaten this type of food on average 10.8 days ago (Van der Heijden 1993b). For the respondents from Yonki these values are 22.4% and 5.3 days ago. On average the Yonki respondents had a meal with some food from animal origin every 1 out of 2.1 days, while this was only 1 out of 3.3 days for the 185 respondents from the high altitude villages which were far from a lake. The higher average cash income of the Yonki respondents may be partly responsible for this, but the reservoir has certainly caused an increase in the number of meals with animal protein for the people living near to it.
4.8 Fisheries problems experienced by the respondents
The fisheries problem mentioned most often by respondents elsewhere in the high altitude areas of the Sepik-Ramu is the lack of fish in the rivers and streams (Van der Heijden 1993b). This problem was mentioned by 69.5% of 117 respondents from 8 villages, followed by the problems experienced as a result of the seasons (55.4% ). Of the Yonki respondents, however, only 12.5% express dissatisfaction with the amounts of fish present in the reservoir. For them seasonal problems, such as a smaller catch during the dry season, are the most important fisheries related problem. This problem was mentioned by 59.4% of the respondents, followed by complaints about the distance between the lake and their village (31.3%) and the small size of the fish caught (25.0% ).
4.9 Preferences for fish species
Common carp was clearly the favourite species for consumption (Table 16), followed by redbreasted tilapia. The latter species only appeared mid-1992 in the catches of the respondents. During the October and December surveys this species was mentioned by 22.3 % of the respondent as their favourite. Common carp was still "Number One" for 49.4% of the respondents interviewed in October and December. Mozambique tilapia is the favourite species of only a few people because of its small size and lack of flesh in Yonki and great number of hard bones.
4.10 Some concluding remarks about the Yonki reservoir fishery and its future
The fish stock of Y onki Reservoir consists of the 4 species mentioned in this report plus Anguilla bicolor an/or A. marmorata. The most abundant species, the mosquito fish Gambusia affinis is the least exploited. It may not be the most suitable species for human consumption, but it may be worthwhile to do a test fishing with big, fine-meshed scope nets, a small fine-meshed trawl, or even with linnets and lights during the night, to find out if the numbers caught make further exploitation worthwhile. Mosquito fish are already consumed by some local people and fresh or dried mosquito fish could be a protein-rich component of livestock feeds.
The fish stock at Yonki Reservoir is at present only very lightly exploited. Besides people, aquatic insects preying on fry and some fish-eating birds, no major predators of adult fish are present in the reservoir. The fish species present may occasionally eat some 24 fish eggs, larvae or small fry when they find them. However, once the fry have reached a certain size only the occasional baited hook or fish-eating bird reduce their chances of survival. This could lead to a fish population consisting mainly of small, stunted specimens. Wright (1980) concluded that the carp population in Kandep Lakes was stunted, and recommended the use of small-meshed gill nets and increased fishing pressure to reduce the number of small fish in order to give the survivors the chance to grow to a decent size. The predatory rainbow trout (Oncorhynchus mykiss) is also present in the Kandep Lakes but it did not seem to be able to check the numbers of small common carp. It is recommended that the fish stocks in Yonki reservoir are monitored further to detect, among other things, the occurrence of stunting. Introduction of a native predatory fish species from within the Sepik-Ramu catchment area may be difficult since few such predatory species exist. This also rules out the possibility to exploit the abundant mosquito fish resource indirectly by utilising a predator.
Fish farming in cages has significantly increased the production of reservoirs elsewhere in Asia (for example, Costa-Pierce et al. 1988). With the high demand for fresh fish in the PNG Highlands, the presence of urban centres such as Kainantu and Goroka and the good accessibility of these centres when coming from Yonki, the testing of this type of fish production in Yonki Reservoir seems worthwhile. It could become a significant source of income for the residents around the lake once its economic and social viability under PNG conditions has been tested and proven.
The use of gill nets in the reservoir has been discouraged by ELCOM, the body which manages the lake. Some of the respondents expressed fear that the increased use of this type of gear would affect the numbers of fish. The present level of exploitation however under-utilises the resource available, and it is doubtful if the major method used at.present (hook and line) will be able to exploit the resources to an optimum level. The fishing methods used at present guarantee a fair distribution of the benefits coming from the resource among the users. It seems on the other hand wasteful not to utilise a protein resource to an optimum sustainable level in an area where animal protein can be considered scarce and has to be supplemented with imported food such as tinned fish and lambflaps. If more efficient gears such as gillnets and others are permitted in the future its· use should be within the framework of a fisheries management plan which promotes sustainable exploitation.
Especially during the dry season the water at the reservoir becomes greenish in colour indicating an abundance of phyto-plankton, and possibly zoo-plankton. The fish species present in the reservoir exploit this resource only indirectly by consuming zooplankton, benthos and detritus. Addition of a phytoplankton feeding fish species could boost the total fish biomass significantly. However, no such species is present in the Sepik-Ramu catchment area. 25 5. REFERENCES
Costa-Pierce, B.A., G.W.Atmadja, P.Effendi and S.Zainal, 1988. Integrated aquaculture systems in the Saguling Reservoir, West Java, Indonesia. p 224-233 in: S. S. de Silva (Ed). Reservoir fishery management and development in Asia. Proceedings of a workshop held in Kathmandu, Nepal, 23-28 November 1987. International Development Research Centre, publication IDRC-264e, Ottawa, Ontario, Canada.
De Silva, S.S., 1988. The reservoir fishery of Asia. Page 19-28 in: S. S. de Silva (Ed). Reservoir fishery management and development in Asia. Proceedings of a workshop held in Kathmandu, Nepal, 23-28 November 1987. International Development Research Centre, publication IDRC-264e, Ottawa, Ontario, Canada.
Heijden, P.G.M. van der, 1993. Survey on economic activities, animal protein intake, fishery activities and fish yields in the Sepik- Ramu catchment area, 1991-1992. Part 1: Methods. Field Document No.18/a of the Sepik River Fish Stock Enhancement Project, FI:PNG/85/001, FAQ, Rome Italy.
Heijden, P.G.M. van der, 1993. Survey on economic activities, animal protein intake, fishery activities and fish yields in the Sepik- Ramu catchment area, 1991-1992. Part 2: Results. Field Document No. 18/b of th~ Sepik River Fish Stock Enhancement Project, FI:PNG/85/001, FAQ, Rome Italy.
Sifa, L.,1988. The principles and strategies of fish culture in Chinese reservoirs. Page 214-223 in: S. S. de Silva (Ed). Reservoir fishery management and development in Asia. Proceedings of a workshop held in Kathmandu, Nepal, 23-28 November 1987. International Development Research Centre, publication IDRC-264e, Ottawa, Ontario, Canada.
Wright, A., 1980. Survey of the Kandep Lakes, Lai Valley, Enga Province. Internal report of the National Department of Fisheries, Port Moresby, Papua New Guinea. 19p. [in Dept. Fisheries & Marine Resources Library/Bibliography, Kanudi]. 26
ANNEX
Length-weight relationships for the fish species
The following length-weight equations were used to estimated the weight of the fish of various sizes: for common carp (Cyprinus carpio):
W = 1.612 x 10-6 x TL3.0087 for the Mozambique tilapia (Oreochromis mossambicus):
W = 1.366 x 10-5 x TL3.0514 for the redbreasted tilapia (Tilapia rendalli):
W = 2.124 x 10-5 x TL 2.948 where Wis weight in grams and TL is Total Length, in mm.