FISHERIES RESEARCH BOARD OF CANADA PROGRESS REPORTS OF THE PACIFIC COAST STATIONS PACIFIC BIOLOGICAL STATION NANAIMO, B.C. AND PACIFIC FISHERIES EXPERIMENT AL STATION 898 RICHARDS STREET VANCOUVER, B.C. No. 74 MARCH. 1948 VANCOUVER, B.C. These Progress reports are issued from time to time to acquaint the fishing industry with some aspects of investigations undertaken by the Fish· eries Research Board of Canada through its Pacific Coast Stations. CONTENTS PROGRESS REPORTS NO. 74 Experiments on the Storage of Frozen Shrimps 0. C. Young and D. H. Taylor J Lakes of the Skeena River Drainage VII. Morrison Lake V. H. McMahon 6 Lakes of the Skeena River Drainage VIII. Lakes of the Lac-da-dah Basin F. C. vVithler 9 Lobsters and Allied Crustacea: Distinguishing Points J. S. T. Gibson 13 Probable Cause of the Browning of· Certain Heat-Processed Fish Products H. L. A. Tan 17 Experirn.ents on the Canning of Freshwater Fish A. W. Lantz 19 Refrigerator . Car Tests. V. D. H. Taylor and J. S. 1'f. Harrison 23 A Note on New Equipment for Determination of .\Vater in Fishery Products Norman E. Cooke 26 EXPERIMENTS ON THE STORAGE OF FROZEN SHRIMPS In issue No. 43 of this series of Progress Reports, experiments on the preparation of shrimps for freezing were described. In those experiments the shrimps were cooked, peeled and blanched before being packed tightly into tin cans then frozen and stored. As indicated in that report the shrimps were packed in the dry condition, that is with no liquid added, and samples had been stored up to 5 weeks at -10°F. without distinguishable organoleptic changes taking place. A continuation of the storage phase of the problem revealed that the storage life of the shrimps prepared q.nd stored in the manner described was approximately 3 months. However, if sufficient tap water ·was added to each can to completely eliminate the air from around the shrimp meats, then the storage life was prolonged to well over a year. The main. objection to storing the cooked shrimp meats in water, however, was that the water leached salt from the meats and left them rather "flat" in fiavour. Therefore a further salting or blanching was neces­ sary to restore the desired saltiness after the stored product had been thawed. As a result, frozen cooked shrimps are not generally stored in water (ice) commercially in Canada, because they cannot be placed directly on the table by the housewife after they have been thawed out. Flooding the frozen shrimp with a brine solution of the proper concentration to give the desired saltiness on thawing readily suggests itself, but the few tests with brine that time permitted in those earlier experiments did not give very encourag­ ing results. The brine seemed to destroy or mask the delicate flavour of the shrimp, also it seemed to promote the development of an "off" flavour arbitrarily described as being rancid. During the latter years of the last war and the early post-war period, little interest was shown by the Canadian fishing industry in the freezing of shrimp. However, early in 1947 interest again began to revive in this product; therefore further experiments were carried out in our laboratories with the various kinds of shrimps caught in southern British Columbia waters. Because of the industry's desire to store shrimp meats in a form that would permit them being eaten without further preparation after thawing, cooked samples were again prepared and stored both dry and in a brine, some dipped in an /-ascorbic acid solution (0.04%) and some in a 2.5% common salt brine containing the above concentration of ascorbic acid. Raw samples were also stored both dry and flooded with pure water. To eliminate variables other than the treatments, the samples were all sealed in tin cans. Freezing was accomplished by m:erely placing the samples in the cold room in which they were to be stored. The temperature of this room fluctuated a maximum of +3°F. about a mean temperature of -19°F. The size of the room was such that the placing of the unfrozen samples in it for freezing would not significantly alter the mean temperature, and since the air was unagitated the freezing of the samples would be moderately slow. 3 Storage period Preparation . of sample 2 months 4 months I 6 months 9 months 1 Raw in shell: Slight discoloration around No detectable 1 No detectable change ·No detectable change beheaded, dry (control) egg cavity, disappeared on change washing. Colom:, texture and flavour excellent Raw in shell: Colour, texture and flavour beheaded, wet (flooded excellent with water) Raw picked: Colour pale, texture ·and dry (control) flavour excellent Raw picked: Colour pale, texture and " wet (flooded with water) flavour excellent Cooked picked: Colour, texture. and .flavour Colour unchanged; texture Colour unchanged; texture dry (control) very good fair; flavour fair fair; flavour poor, "sweet­ ness" entirely gone Cooked picked : Colour, texture and flavour Similar to sample just Colour unchanged; texture dry dipped in 0.04% very good above fair; flavour fair /-ascorbic acid solution Cooked picked : Colour and texture very No detectable change No detectable change wet (flooded with water) good; flavour "flat" (very good after re-blanching) Cooked picked: Colour, texture and flavour Colour and texture un­ Colour and texture good ; wet (:flooded· with 2.5% very good changed, flavour fair (lack­ flavour fair brine) ing "sweetness") Cooked p1cked : Colclur, texture and flavour Similar to sample just Similar to sample just wet (in brine + ascorbic very good above above. acid) l===============~=--==============-======~cc=========-~·=·============~~==================-~-=-~c_c.c_~~~'-'--"~o-- Three kinds of shrimps were used in, the tests, namely: pinks, side stripes and prawns. The raw in the shell, raw picked, and cooked picked samples were prepared in the various. ways stated in the first column of the accompanying table. The cooked samples were prepared by cooking for approximately 5 minutes in boiling tap water, then cooled, picked and blanched for 90 seconds in boiling 20% common salt brine, then dipped for several seconds in cold water before being given the indicated treatments. for storage. The stored raw samples after being thawed out for testing were cooked under conditions similar to those for the samples cooked before storage. The results which were typical for the three kinds of shrimps tested are given in the accompanying table. ·The results indicated rather convincingly that frozen shrimps are best preserved in their shells raw, beheaded, and flooded with water to prevent desiccation and oxidation. The raw shrimps. that were peeled before freezing retained their texture and flavour but their appearance was decidedly unattractive due to the loss of the pink colour which washes off readily in the raw state. The cooked samples stored rather well up to 4 months under the conditions of our storage room. By 6 months, however, the "sweet" flavour characteristic of fresh shrimps was gone. This was more pronounced in the dry (control) and the samples stored in brine only. The /-ascorbic acid with the brine appeared to have some effect in retaining the flavour, but in comparison with the control, the dry sample merely dipped in a solution of I-ascorbic acid was not detectably affected by the treatment. These experiments confirmed the earlier work by showing that flooding the cooked samples with water preserved the "sweet" flavour, thus indic,ating that salt has the effect of destroying or masking this particular taste factor. Pacific Fisheries Experimental Station 0. C. Young D. H. Taylor Winter Survey of Lakelse Lake Recently from January 30 to February 5, Mr. J. R. Brett, Assistant Biologist, Pacific Biological Station, assisted by Mr. V. H. B. Giraud, Domin­ ion Fisheries Inspector at Terrace, made a short survey of winter conditions at Lakelse lake, Skeena river, one centre of important sockeye salmon studies. Examination of certain previously marked 'spawning redds showed survival thus far to be high at approximately 83%. The physical conditions such as low temperature and the resulting freezing were not so severe as to cause alarm. From gill-net sets made under the ice it was found th,?-t the distribution of lake fish and their food habits were quite different from those during the summer. This short inspection has confirmed the advisability of winter survey and demonstrated the abundance of information which may be obtaim;d therefrom. 5 LAKES OF THE SKEENA RIVER DRAINAGE VII. MORRISON LAKE* The chief objective in in\restigating the lakes of the Skeena river drainage has been to gather information ·relative to the natural propagation of the sockeye salmon, Oncorhynchus nerka1 in an effort to discover limiting factors. and to outline methods by which the efficiency of propagation can be increased. In previous issues of these Progress Reports the characteristics of ten bodies of water of varying size have been dicussed-Lakelse, Morice, Kitwanga, Kitsumgallum, Bear, Sustut, Asitka, Johanson, Darb and Spawning lakes. Morrison, herein described, is the eleventh of the group and is of particular importance since it forms part of the Babine system where as much as half of the total sockeye s"almon escapement to the Skeena may spawn. The first exploratio11 of the .area was undertaken in the summer of 1945 with the prime object of procuring a general picture of the lake and its biological features. At that time a base camp was established at the southen1 end near the site of the old hatchery which had been operated by the Dominion DeJ;>artment of Fisheries for many years prior to its closure in 1938. During 1946 and 1947, more prolonged and detailed studies were conducted at several periods throughout each summer.