Appendix 4 to Field Document 2 sets out the proposed project work programme for the duration of the project. The status of this work programme is discussed below, section by section.
The individual members of the Lake Investigation Team have responded well to their training and are now working well together and coordinate and cooperate well in the field work and the processing of samples and data.
Considerable progress has been made in the recording of data in the field and the subsequent entry of these data into the computer for analysis. This section of the planned work programme is progressing approximately to the expected tune-table.
Mr Yang Hongzhi, Ms Zhang Lijuan and Ms Ying Xiuli have benefitted well from the on-the-job training. Ms Ying Xiuli also attended a short course on computer techniques held in Xining in September. The team members are becoming very competent in entering and analyzing data on the Lotus 123 programme, carrying out statistical analyses and presenting the results graphically. Mr Yang Honzhi is competent to use the Framework database and the WordPerfect wordprocessing programme for English texts. It is hoped to obtain a Chinese language wordprocessing programme from local sources.
3. Logbook data
Using the Lotus 123 release 3 programme, the information from each log-book has been entered onto a spreadsheet, with the operators (Ms Ying Xiuli and Ms Zhang Lijuan) interpreting the log-book entries with respect to the area of the lake fished and the weather conditions. Using this database the information is being sorted to indicate the changes in fishing activity, catch-per-unit-effort (CPUE) and total catch throughout the various seasons of the year, the weather conditions and the area of the lake fished.
The size of these databases and the complexity of the analyses have caused us to reach the limit of the capacity of the desk-top computer and steps are being taken to upgrade this and to replace the Lotus 123 programme, which has proved to be faulty, with an updated and unproved version.
The first results of this work are presented in Appendix 1 to this report.
Sampling of the landings from the trawlers continues and these data are entered onto the Lotus 123 spreadsheet. The spreadsheet allows the analyses of the trawl-net selection, the comparison of size and weight of the fish caught over the years, and the production of growth rate curves for the fish. The initial results of these analyses are presented in Appendix 2.
The sample data of fish taken from the experimental fleets of monofilament gill-nets are entered on to the Lotus 123 spreadsheet and analyzed to provide evidence of age-group cohorts in the population, growth rate curves, and changes in the population age-group make-up in different areas of the lake.
Additional data are being derived from the results of the seine netting and electrofishing of the river habitats.
A considerable amount of hydrological and meteorological data has been obtained from the records of the Hydraulic General Station in Xining. These data are now being processed to provide a historical record of conditions on the lake and its catchment.
The bibliographic database which has been entered on the Framework database programme, is updated as necessary.
Apart from the delays in delivery which have been documented in the report for 1990, there have been no serious problems, or work programme disruption, associated with the equipment in this current year. The additional equipment that has been ordered has arrived or is on the way.
The converted trawler continues to prove quite adequate for the work of the team and the development of the project work programme. At the start of the sampling season of the current year, the modifications requested in the last report were more or less completed. The boat is safer to use, and the winch and boom for handling the samplers has proved very practical in use.
Living accommodation is much improved and a full set of interior and deck working lights and electrical circuits are now in place.
As must be anticipated with a vessel of this nature there will be a continual need for ongoing repairs and rehabilitation and every effort should be made to keep ahead of small problems as they arise. It is recommended that the vessel is given a general check and any work needed, before the beginning of next sampling season.
Considerable success has been achieved in the sampling of the fish populations on their breeding migration, in particular with the use of the electro-fishing apparatus. However, although sampling has been carried out 8 times during the breeding season, the work in the river has concentrated on providing adults for the breeding trials at the hatchery in Xining. It is hoped that throughout the next sampling season more attention will be given to the population biology of these important breeding stocks.
There has been only a cursory survey of the spawning areas, which occupy many hectares of braided stream bed which extend for apparently more than 100 km upstream of the Buha bridge river crossing. Other typical spawning areas have been identified on other rivers along the north shore, particularly the Sha Liu, but river control works have created impassable barriers to the passage of fish so that these areas no longer have any function in breeding and/or recruitment to the fishable stocks.
Two initial surveys have been made of the spawning areas in the Buha river some 80 km upstream of the Buha bridge. Populations samples were taken and measured for total biomass and population structure assessment.
Useful meteorological and lake level data have been purchased from the Hydraulic General Station in Xining. These data are still being worked up.
It has proved more difficult to identify the changes that have taken place on the inflow rivers and their catchments. Whatever information is available is being actively sought, as the changes affecting the inflow rivers, especially those of the west and north shores, will have important effects on the pattern of recruitment of the naked carp to the fishable populations.
The 300 adult fish caught on the spawning grounds and 1,200 taken from the trawl catch have been measured, tagged and released during this current season. These are in addition to the 20 fish that were tagged from Buha river catches towards the end of the 1990 season.
To date there have been no returns of fishes tagged on the breeding grounds or from open water catches.
The limnological investigations are intended to provide an indication of the water masses that make up the lake, as a guide to the possible part these may play in the production and location of the fish populations. The results of these investigations combined with historical data on the hydrology of the lake and the meteorology of its catchment, can offer supporting data for the interpretation of data derived from the investigations of the biology of the fisheries.
Monthly sampling has been carried out on the inflow streams. Large fluctuations in chemical and physical parameters have been observed, and these data are to be analyzed. Despite these fluctuations, it is probably the suspended solid load and changes in flow that are the more important in controlling the breeding biology of the naked carp.
The shallow waters and edge habitats have not been sampled. This work will await the arrival of an easily portable boat. An inflatable boat is on order and awaiting delivery.
4. Open lake waters
After irregular, familiarisation, sampling in the early part of the year, it has proved possible to make the first of the comprehensive sampling trips before the close of the season. These trips will provide lake wide transects to include experimental fishing, bottom sampling and plankton sampling. At a number of stations limnological parameters throughout the water column are measured. This work was somewhat curtailed by the lack of all of the functions of the limnological profiler, but sufficient data are now available to provide an indication of the limnological conditions in the lake throughout the seasons of the year.
The initial trials with the echosounder have been completed and it is hoped that this will be brought into full use during the 1992 sampling season.
The programme to sample the bottom fauna and flora in both the main lake areas and the shallow waters and inflow streams, has been slow to start and is behind schedule. The major items of sampling equipment were not available until the beginning of the current year, and for much of the year the team has been gaining familiarity with its use on the lake. The development of this work has also been retarded by the change in the team responsibilities and the departure from the team of Mr Wang Jiling who was formerly in charge of these investigations.
The initial quantitative sampling of the benthos of a lake transect has now been completed and the samples have still to be worked up.
The “run” of breeding fish was apparently late this year, with the first fish ascending the Buha river when its flow began to increase during the third week in May.
Sampling in the Buha river on 23 April by electrofishing, dip nets and seine net produced only a small number of loach and year 0 naked carp. This is the first confirmation that the young fish hatched towards the end of the previous summer are able to overwinter in the river. A considerable dipteral emergence was taking place at this time, when there was still some ice remaining and the river water temperature was 5–7°C.
On 28 May electrofishing at the Buha bridge was undertaken in collaboration with Mr Qu Weiliang, from Heilongjian Fishery Institute, in order to obtain samples of ripe adults for the breeding trials that are taking place at the Provincial Fingerling Farm at Xining. Using a block net upstream this activity was very successful producing a considerable number of mature naked carp for transfer to the Xining hatchery. This electrofishing was continued by Mr Qu and his assistants.
The team is now well trained in the use of the experimental monofilament gill-net fleet and the processing of the fish. The fleet has been set 15 times in the bay adjacent to the Fish Factory. A considerable quantity of data are available on the net-selectivity of this fleet and these data are now being processed to reveal the expected cohorts in the fish population. The catches have been deficient in the smaller age/size groups. This may be due to these small-fish populations occupying specific areas of the lake, which have not yet been sampled, or that the nets are not capable of catching these smaller sizes. Smaller mesh nets are being purchased in order to investigate this further.
The data currently being worked up from these samples include age-length analyses, weight-length analyses, body weight-viscera weight relationships, gonad state and gut contents.
The data obtained from the experimental gill net fishing have been supplemented by the continuation of the measurement and analysis of samples from the commercial trawl catches. These latter are important as there has been a change in trawler size and net configuration during the last two years and it will be necessary to compare current data with the run of data from the past years.
Excellent progress has been made throughout the year in tracking down sources of data on the commercial catch. Of particular value has been access to fishing boat log-books, and the early statistics of the factory output. Further and more specific information about fishing activity, both legitimate and uncontrolled, is now becoming available.
Throughout the year a considerable effort has been made to track down the whereabouts of the log-books submitted by the trawler skippers. Log-books from 1980 to the present (with the exception of 1986 and part of 1990) have been located at the Fish Factory and these have been made available to the Lake Investigation Team. The data provided in these records have proved very valuable. It is understood that the log-books for the 20 years previous to 1980 have been lost or destroyed and the employee who was in charge of these is now retired and is no longer available for discussions about this information source.
The log-book information has all been extracted and entered onto the computer spreadsheet databases. Currently this is being analyzed to provide a picture of fishing activity and the catches obtained from the various areas of the lake and during the different months of the fishing season.
A further analysis has been carried out to indicate the changes in catch-per-unit-effort (CPUE) for fishing carried out in a representative area of the lake. The preliminary results of this analysis is discussed in Appendix 1.
These CPUE analyses and the comparison of the size ranges caught in the trawls that have been made at intervals, indicate that there has been little change in the fish populations and their exploitation since the initial large catches of large size fish resulting from the opening of the virgin fishery to exploitation were replaced by a sustainable off-take. Appendix 1 presents and initial assessment of these data.
Apart from the official published statistics, some additional data on the total catches from the lake since it was open to exploitation have also been discovered at the Fish Factory. This information is also being incorporated into the data being analyzed by the team (see Appendix 1).