Tuatara: Volume 14, Issue 3, December 1966
A simple and convenient method of cataloguing a marine fish scale collection
A simple and convenient method of cataloguing a marine fish scale collection
In a pioneer study on a species the investigator collects many samples before undertaking his final interpretation and analysis, so that at any one time he is dealing with samples collected from various localities and at different dates.
Once basic age-growth principles have been established a ‘monitoring’ scale-reading programme is often continued, with the investigator collecting, reading, and filing a series of monthly or otherwise regular samples. The scales, or plastic impressions of them, are usually stored for future workers who may need them for reinterpretation of critical phases in the life history of the species or for a study of the change of its growth rate with time; rarely does the first worker publish sufficient data to allow this without reference to his original material.
Our experience in the Fisheries Research Division has shown that a scale collection rapidly becomes impractical to use if it is inadequately catalogued. The existence of several uncatalogued collections in the Fisheries Research Division (Eldon, in press) prompted the author to plan an appropriate system for cataloguing the large number of scale samples needed during his investigation of ageing techniques, growth rates and population characteristics of the snapper, Chrysophrys auratus Forster. This system is similar to that described by Morgans (1965) for cataloguing biological specimens, but having to deal with only one type of sample it is much simpler; in fact the collection itself can be used as its own catalogue. With minor alterations it has worked very well over four years and it is described here in the hope that other fisheries workers in New Zealand may adopt similar systems and so facilitate exchange of research material.
Collection of Scale Samples
About 15 scales are taken from a specified site on the fish's left side and put between a folded slip of paper and into a labelled page 134 envelope. The information recorded for each fish includes: species, collection date, locality, length, weight, sex. and the collector's initials. Scale-sampling time in the field is usually limited, and only locality, length, and, if taken, sex and weight are written down at the time, the other entries being completed as soon as possible afterwards.
Fisheries Research Division Station Numbers
The field recording of locality and date, plus other information for which there is no room on the scale envelope, is simplified by use of a Station Number for each locality at which any collection or significant observation is made. These numbers run serially from the beginning of each year, and with appropriate station data are entered in a permanent Station Register, one copy of which is held at the Fisheries Research Division at Wellington. There are 24 sets of available Station Numbers, each prefixed by a letter (I and O are omitted for the risk of confusion with numerals); each may run from 1 to 1,000 in any one year. Each number is suffixed by the last two numbers of the year in which the station was made. The Marine Department research vessel Ikatere always uses the letter K, so that her 1966 stations run: K 1-66, K 2-66, K 3-66, etc., up to a possible K 999-66. Her 1967 stations would start K 1-67. This system follows one used successfully by the New Zealand Oceanographic Institute for many years. Fig. 1 gives an example of station data recorded by the Ikatere.
The Scale Sample Collection
The basic division of any collection is into species. The snapper scale collection is only one of several which are being developed by the Fisheries Research Division.
The first division of the snapper collection is into geographical regions: West Northland, East Northland, Hauraki Gulf, Bay of Plenty, Poverty and Hawke Bays, Wellington and Cook Strait, Porirua Harbour, Kapiti Island, and Tasman and Golden Bays. Others may be added later. The sizes of these regions vary widely; each size is best determined by such factors as the oceanographic uniformity of an area, the area covered during different field trips, and the likelihood that some areas may later be chosen for more intensive sampling (these should in general be smaller than those where few collections will be made).
Samples from a single region are subdivided in the following order (see also Table 1):
By month (an exception may be made when a single collection trip includes part of one month and a few days of another; all samples are then included under the predominant month).page 135
|Year||Month||Length||Locality Name||No. Station|
|(x + 0.5)||A||a|
|(x + 1.0)||A||a|
|(x + 1.5)||A||a|
|(x + 0.5)||A||a|
By length. Samples are arranged in order of increasing body length; 0.5 cm is the basic unit of measurement adopted for the snapper collection, but snapper less than 15 cm are recorded to the nearest millimetre.
By locality (i.e., particular locality within the region).
By station number.
When all of one month's samples from a region have been collected and sorted as above they are numbered serially, e.g., Hauraki Gulf 1, Hauraki Gulf 2, etc., and stored separately from those of other regions (sets of partitioned box-files have been found most convenient). Samples from succeeding months are allocated successively higher numbers within each regional series.page 137
As long as the order of category subdivision is kept in mind the collection can be used satisfactorily without any catalogue. Scale sample envelopes temporarily removed for study can be quickly returned to their correct places by reference to the serial number on each.
The Mounted Scale Collection
Scales temporarily or permanently mounted for microscopic study can be easily identified by the serial number alone; this has the added advantage that the size and other particulars of each fish are not known at the time of age interpretation, which thus prevents a bias towards an ‘expected’ age. Fish scales can be mounted in several ways: as impressions in sheet plastic or as whole mounts between two microscope slides cemented together by Canada balsam or fastened temporarily by adhesive tape.
The Scale Sample Catalogue
A catalogue makes the selection of appropriate scale samples easier. It can be compiled by hand, but is much more rapidly and neatly done by dictation to a typist. Part of the Hauraki Gulf section of the snapper scale catalogue is shown in Table 2.
In the Year, Date, Sex, Collected by, and Locality and Station No. columns a blank entry implies a continuation of the entry above; thus Nos. 2140-2142 represent three snapper 20.0 cm in length caught at Kawau Island on May 12, 1965. In the Remarks column a blank implies that no entry was made. In the Mounted column a plus sign indicates that a sample has been permanently mounted, and a blank shows that it is unmounted; this is kept up to date as samples are prepared and mounted for examination. An early attempt to use only one form of entry led to considerable unnecessary repetition, so the above compromise was adopted.
An investigator wishing to re-examine previously collected scales thus has three sources of information, each linked to a single catalogue which is itself quite informative.
The original scale sample collection. Each envelope is fully labelled so that the collection can be used to a certain extent without a catalogue. A new catalogue can also be copied directly from the data on the serially arranged envelopes if the original is ever lost.
Mounted scales ready for microscopic examination, identified by the region and the serial number, e.g., Hauraki Gulf, 2140, and stored in geographical and numerical order.page 138
A Station Register which gives relevant information on each collection locality and allows the identification of all other collections and data records made at each station.
Two examples of the practical use of the catalogue are given below to illustrate its value.
To check whether a sample exists for a 20.5 cm snapper from Kawau Island in May 1965 (the worker may decide that this is a critical size, locality, and date for some phenomenon he is investigating) he turns to the Snapper Catalogue, Hauraki Gulf section, and to the May 1965 page (see Table 2). Hauraki Gulf Nos. 2148 and 2149 meet his requirements, and he can see immediately that a permanent mount has been made of each.
|Snapper Area: Hauraki Gulf|
|Code No.||Year||Date||Lgth (cm)||Sex||Coll. by||Mounted||Locality||Station No.||Remarks|
|2140||1965||May||12||20.0||—||LJP||+||Kawau I.||K 25/65|
|2143||May 11||20.0||F||Cradock Ch.||K 19/65|
|2145||May 17||20.5||—||N. Noises I.||K 28/65||Deformed jaw|
|2147||May 12||20.5||F||Pakiri Bch||K 24/65|
|2148||20.5||—||+||Kawau I.||K 25/65|
To check the growth rate of deformed snapper against snapper of a similar length he scans the Remarks column of the catalogue. Hauraki Gulf No. 2145 has a deformed jaw and can be compared with No. 2146, a normal fish of identical length caught at the same station, and with Nos. 2147-2149, fish of the same length caught at adjacent stations. Permanent mounts have been made only for Nos. 2148 and 2149; the others must be made up from the original scale sample collection.
Eldon, G. A., (in press). List of Freshwater Fish Scales Held at Fisheries Research Division, Wellington. Fisheries Research Division (Marine Department) Occasional Publication No. 2.
Morgans, J. F. C., 1965 A Simple and Flexible Cataloguing System for Biological Collections, Large or Small. Tuatara 13 (2): 116-21.