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. Morrison lake, at approximately 55° iS' N. and 126° 20' W. and lying parallel to the northern arm of Babine lake, is fed mainly by two fairly large streams at its northern end, namely Haul and Salmon creeks which in turn arise in lakes of the same names farther to the north. It is drained from the 'southern encl through Morrison river into the Morrison or Hatchery arm of Babine lake. Thus in contrast to such lakes as Lakelse which are at the head of a drainage and fed only by small tributary creeks-a "one lake system"-Morrison is approximately in the middle of a large drainage area. This situation makes more involved any consideration of the suitability of the area for sockeye salmon production and requires special thought and analysis. The lake is approximately ten miles in length and rarely exceeds one mile in width. On the basis of water depth,it may be divided roughly into three parts, a northern fairly shallow portion not more than 20 metres (61 feet) deep, a central area with a much lower basin with depths over 60 metres (183 feet) and a southern third very similar to the northern. The average depth is about 20 metres (61 feet). Around the shoreline except iii the northern portion which was denuded by. fires in 1922, p,re thick stands of coniferous trees-spruce, pine and hemlock. Large boulders, amongst which are interspersed scattered .reed beds., line almost all the water's edge and extend out .into the lake to a depth of about 2 metres (6 feet). The lake floor, as determined from dredging, appears to be composed almost entirely of fine adhesive mud in which bottom
* The seventh in a series presenting general information on the lakes of the Skeena river drainage particularly as it affects salmon production. ' 6 SALMON CR.
MORRISON LAKE
MORRISON LAKE
SCALE Mil.ES 1·0 1 l I METRE= 3.28 FEET ,Map of Moi:ri~on lake showing, bo,ttom \,contours ,and tributary i.treams 7 organisms are extremely scarce. The samples contained only a few small crustaceans and worms and were completely lacking in molluscs. The lake water is relatively clear and cold, ranging in temperatures during the summer of 1946 from a minimum of 4.8°C. (40.6°F.) at 60 metres (183 feet) to 17.2°C. (63.0~F.) at the surface. The plankton population and more particularly that portion used by young salmon as food, viz, copepods, cladocerans, etc., is present in Morrison in relatively great abundance in comparison with other lakes in the Skeena system. The commonest forms are the copepods Cyclops and Diaptomtts. It is known that fewer than 50,000 adult sockeye salmon enter ·the Morrison drainage in the autumn to spawn. As a result of the position of the lake, it is certain that all the progency do not utilize this body of water alone for their firs( year's residence. Undoubtedly some remain in the lakes to the north and others drop back to Morrison arm in Babine lake. On the basis of the food present, if all other factors were normal and adequate, Morrison lake could support far greater numbers of young salmon than are now present even up to and perhaps more than the total progeny from the whole run. The peculiar feeding habit of the eastern whitefish, Coregonus clupeaformis, · in the area offers at least a partial explanation for the dearth of young sockeye in relation to the food present. Analyses of over one hundred stomachs have shown that the diet is almost entirely copepods although the whitefish is generally assumed to be, and has in most cases been proven to be, a bottom feeder in. all the larger stage'S. In Morrison lake, where it is relatively very abundant making up about one half of all the fish taken in the gill nets, it thus becomes a serious competitor for sockeye salmon young. To this competition may be added the effect of other species which utilize the plankton to a lesser degree, namely the peamouth chub, Mylo cheilus caurinus, the Rocky Mountain whitefish, Prosopium williamsoni, and the kokanee, Oncorhynchus nerka kennerlyi, as well as the young of other salmonoid species. Direct predation on young sockeye salmon is of some consequence. Two of the five known predators, the lake trout, Cristivomer namaycush, and the burbot (ling), Lota maculosa, probably do the most harm bei:.;ause they are large, voracious and present in fair abundance. The rainbow trout, Salrno gairdnerii, the cutthroat trout, Salmo clarkii, and the squawfish, Ptycho cheilus oregonensis, are' rhuch less common, and in at least the case of the cutthroat the food taken consists mainly of organisms other than fish. It would appear that the salmon spawning grounds in this drainage are rather limited in extent. Morrison river, joining the lake to Babine lake, is recognized as an excellent spawning area. Salmon creek to the north shows a fair amount of spawning gravel. Muddy Haul creek apparently does not carry salmon and the other small streams emptying into the lake are of little consequence even in the aggregate in providing suitable redds. There is a possibility that the available beds could be improved by judicious cribbing and clearing of the streams, but the final decision as to method should await further concentrated study. In summary the following would appear to be the situation in Morrison lake insofar as sockeye salmon production is concerned. The plankton 8 production is relatively high but the eastern whitefish, adapted to plankton apparently as a result of the lack of their usual ~iet of bottom organisms, are using up much of the available food. It is of course possible that the sockeye young were never present in large numbers and, in such a case, the whitefish could not be considered as having replaced the salmon in the food cycle of the lake. The probability of this latter situation is indicated by the definitely limited spawning grounds of the system. Morrison lake resembles most closely those lakes of the Skeena drainage designated as Class 2, i.e., "rather shallow bodies of water, clear, of moderate temperature and abundant in plant life." It is, however, .deeper than the average of the type and not outstanding in its production of flora. The writer wishes to extend his thanks to Messrs. W. R. Hourston, M. P. Shepard and H. Godfrey for their able assistance in the collection and recording of the data. He is also indebted to Dr. A. L. Pritchard for guidance and help in the preparation of this paper. · Pacific Biological Sta/Jon V. H. McMahon LAKES OF THE SKEENA RIVER DRAINAGE VIII. LAKES OF THE LAC-DA-DAH BASIN* To anyone faced with the investigation of the lakes of the Skeena drainage, one of the first problems to be solved is that of transportation. Particularly is this true of the Lac-da-dah basin, draining into the Kispiox river, which can be classified as one of the less accessible spawning areas. Unless air transport with its reiative comfort is utilized, the investigator must resort to the older method of Indian pack-horse travel. This involves roughly paralleling on horseback and on foot the route. taken by the adult salmon on their way to the spawning grounds of the Lac-da-dah. Thus, one leaves Hazelton, at the junction of the Skeena and Bulkley, to proceed northward for eight miles along the Skeena river to the Indian village of Kispiox, which is situated at the mouth of the Kispiox river. Turning in a north-westerly direction, the trail follows the east bank of the Kispiox river past Grouse, Scounsnosit, Sweetin and Mongeese• creeks flowing into the main stream. One of the highlights of the difficult four day trip is thundering Kitwangulf canyon, which presents the upper limit of migration for the pink salmon, Oncorhynchus gorbuscha. At the entrance of Stephens creek. on turning westerly, the investigator arrives at Stephens lakes and thereby enters the Lac-da-dah, having followed the same route as the migrating salmon for at least 60 miles. * The eighth in a. series presenting general information on the lakes of Skeena river drainage particularly as it affects salmon production. 9 The Lac-da-dah, a.chain of three J;;tkes lying at approximately 55° 41' N. and 128° 40' W., is 40 miles directly NNW of Hazelton, and 70 miles east of the Portland cangl. The drainage boundaries are marked by mountains which separate the area from the Cranberry drainage to the west and the Nass drainage. to the north. Between the lakes and the Kispiox river are small hills whose lower portions run into marshland. Over all the surround ing territory is a thick growth of spruce under which the ground is deeply carpeted with moss, characteristic of the rainy forest belt along the coast. Swan lake, the largest and uppermost of the lakes in the system, exhibits the most irregular shoreline and bottom configuration of the three. This is reflected by the forty-nine odd-shaped islands, which vary in size from over a mile in length to mere pinnacles of the underlying bedrock whose ridges; running in an east-west direction, project erratically above the surface. By comparison with the seven-mile length of Swan lake, St.ephens lake is only four miles in length, and as can be seen from the accompanying map, is shallower and somewhat more regular in shape. Club lake, with a shallow muddy bottom, out of which flows Club creek, forms the intermediate link in the chain. With their arrival in the area, the three species of salmon which migrate as far as the Lac-da-dah distribute themselves over the spawning grounds according to the inclination of the species. Accordingly, Stephens creek, draining out of Stephens lake, supports a small run of spring salmon, 0. tshawytscha, and coho, 0. kisutch, on approximately a quarter mile of good spawning redds. The sockeye, 0. nerka, proceed through Stephens lake to Club creek, where the majority of this species arriving in the area tends to spawn. Although, a considerable portion of Club creek is given over to gravel suitable for salmon redds, the sockeye can be seen in places actively spawning over boulders six to eight inches in diameter. This unusual behaviour is seldom observed in other streams of the Skeena. For those sockeye passing through Club lake' into Swan lake, the remaining stream of any size is Falls creek which, because of its limited spawning area, probably supports no more than a thousand fish at any time. Since sockeye in numbers considerably greater thah this can be seen at the creek mouth in late August, and ar.e often caught in net-sets widely dispersed over the lake, it is quite likely that those, which do not utilize the aforementioned creeks spawn on the gravelly shores of Swan lake. Of all the limiting factors of sockeye production in the Lac-da-dah, the most obvious is t.hat of restricted spawning ground area~ For the sockeye fry which hatch from the redds in the following spring, the lake environment which they enter is abundantly charged with food. Plankton hauls taken during August show that the plankton community tends to be dominated by copepods, represented by Heterocop.e septentrionalis and Cyclops sp. Cladocerans are fewer and probably provide a smaller portion of the young sockeye diet. Heteroco pe is unusual in its distribution in the Skeena drainage, being present in the Babine, Bear and Lac-da-dah lakes, but being absent in Lakelse or Morice lakes. Both Swan and Stephens lakes exhibit a tenacious thermal stratification during the summer months. The surface temperature of Swan lake reaches 16B0 C. (60.5°F.), while at 64 mettes (210 feet), the greatest depth dis covered in the lake, the temperature is only 4.3°C. ( 40°F.). Probably 10 LAKES OF THE LAC-DA-DAH BASIN 6 tMILES {KM· DEPTH CONTOURS AT 10 AND20METRt INTERVALS 1METRE=3·2BFEE.T LAKE Map of the Lac-da-dah lakes showing tributary s,treams and bottom contours at 10-, 20-, 40- and 60-metre intervals. 11 because of the greater surface exposed to wind action, this body of water shows more heat transfer than Stephens lake whose surface reaches 20.3°C. (60°F.) and whose bottom water remains as cold as. 5.0°C. (41°F). At all depths and temperatures, young salmon would find a sufficient supply of dissolved oxygen under summer conditions. The presence of two predator fish in the lake environment may be a limiting factor in the survival of ~ockeye fry. For the dolly varden char, Salvelinus malma, and the rainbow trout, Salmo gairdnerti, which are taken fairly abundantly in ·nets set in both Swan and Stephens lakes, the average volume of young sockeye in the stomachs may reach 30% and 20% re spectively. These amounts could certainly account for a large number of fry throughout the year. A bizarre feature of the dolly's diet is its predation on a land mammal, the red-backed mouse, Evotomys sp. In some years these mice are quite plentiful in the Lac-da-dah area and those which accidentally fall into the lake are eaten by the char. No direct competitor for the plankton food supply exists in the Lac-da dah drainage. The most common fish in both lakes is the long-nosed sucker, Catostomus catostomus, which is particularly abundant in Stephens lake where a shallow muddy bottom and abundant growth of water-weed, Potamogeton sp., favour a large number of bottom organisms. Other bottom fe~ders, the Rocky mountain whitefish, Prosopittm williamsoni, and eastern whitefish, Core gonus clupeaformis, are also abundant, as if to fill in the niche occupied by the peamouth, Mylocheilus cattrinus, which is present in most of the lakes of the Skeena drainage, but notably absent in the favourable conditions of Stephens lake. Rarely caught in gill nets, but taken readily by hand seine, is the bull head, Cot/us asper, which occupies the shallow water of the shoreline. Because the area is remote and quite untrammelled except for the occasional passing Indian trapper, the wild-life is relatively untouched. In the late summer and fall, such ordinarily solitary animals as the grizzly bear and eagle gather to feed on the spawned-out salmon on the redds (somewhat to the dismay of the nervous investigator). Ravens keep up a raucous chorus during the day, and owls continue the calls at night. Wolf and coyote can be heard ranging the foothills at dusk, and in autumn the moose emerge to feed on the water weeds on the lake shore. Beaver and mink can be seen along the lake shore and the creek beds. Stephens lake belongs to the second category of lakes of the Skeena drainage since it is one of the "rather shallow bodies of water, clear, of moderate temperature, and abundant in plant life." Because Swan lake is relatively deep, it could better be called Intermediate. It is clear and of moderate temperature, but does not have the glacial characteristic of the first category of lakes. The writer wishes to thank Mr. Oscar Schmuland who made the initial trip to the area in 1945, also Mr. Tommy Jack, who worked so conscientiously as guide and general camp-life advisor. Dr. A. L. Pritchard, in charge of the Skeena river investigation, arranged the numerous details of transporta tion and supplies. Pacific Biological Station F. C. Withler 12 LOBSTERS AND ALLIED CRUSTACEA: DISTINGUISHING POINTS Since the planting of Atlantic lobsters in a lagoon on Lasqueti island, British Columbia, in the summer of 1946, widespread interest has been aroused in them. From time to time and in several localities fishermen and others have reported the capture of various crustacea which they believed to be lobsters connected with the experiment. The purpose of the present article is to point out the essential differences by which lobsters may be distinguished from other creatures to which they bear a superficial resemblance. Pri:p.cipally these are crayfishes, shrimps and prawns. These animals all belong to the Decapod order of the Crustacea. The Decapods have their bodies divided into twenty-one segments, each of which, except the last, bears an appendage or limb. The first six segments comprise the head, the next eight the thorax, and these fourteen are fused together into _the cephalothorax. The last seven segments form the abdomen. The appendages are. adapted in different parts of the body to perfprm varying functions; thus, in the head segments they .are specialized as sense organs (eye;;, antennules, antennae) and mouth parts. In the thoracic segments the first tl;iree pairs of appendages, the maxilli9eds, are concerned with maintaining a 'current of water past: the· g~lls and passing food to the mouth, and the last five, the pereiopods, are the walking legs, one or more of which may be further modified to .serve as chelae, or claws with forceps. The appendages of the abdominal segments, the. pleopods, ar~ basically concerned with swifrttning, but sorne of them.are generally adapted to s~rve other functions cofic~rned with copulation and, in the female, _the 'carrying of the eggs. The twentieth segm~nt bears .the uropbds, or. tailfeet, which with the telson ( twenty~first segment) constitute the tai~ fan: . In the different 'groups of Decapods varying habits of' life have caused characteristic differei].9es in the/elativeshapes qnd sizes of the·.<,lppendages and these help very m.aterially in identifyin~(the animals. The nrost obvious difference, perhaps, is that between the swimming types-the shrimps and prawns-and the bottom creeping ones-the crabs, crayfish and lobsters. Shrimps and Prawns (Figures 1 ·and 2). Nearly always these have the body laterally compressed, i.e., sides flattened and body. thinner than deep, as opposed to the dorso-ventral compression, i.e .. , body flattened on top and. bottom and much wider than deep, found in the bottom crawling forms. The lateral compression is an adaptation to give greater stability while swimming. Similarly the pereiopods and pleopods are adapted to the swim ming habit, the pereiopods being slender and not well formed for walking while the pleopods are well developed and efficient swimming· organs. Shrimps and prawns, incidentally, do not comprise two natural groups 6£ crustacea. They are, rather, loosely applied terms which differentiate the small species, generally called shrimps, from the large ones, usually called prawns. Crayfish, Lobsters.. Crabs, Ghost Shrimps. These organisms show a definite adaptation to a bottom living and bottom creeping habit. The· body is dorso-ventrally flattened in a way which increases stability while walking, the pereiopods or walking legs are relatively tough (see figs. 3 and 4) and the pleopods are reduced and not generally used for swimming. 13 Fig. L The Shrimp, Crangon munita Fig. 2. The Prawn, Panda/us platyceros Fig. 3. The Crayfish, Astacus potamohius 14 Fig. 4. The Atlantic Lobster, Homarus americanus Fig. 5. The Atlantic Lobster. Note the asymmetry of the claws, the lef,t claw being the slende1rer, adapted for cutting and tearing, while the other is more heavily built and adapted for crushing. Fig. 6 Ghost Shrimps, Callianassa californensis 15 Crayfish and lobsters belong to the same group of crustacea, the members of which are characteristic ally lobsteFlike in appear ance. The first pair of pereiopods or walking legs are developed to form the large chelae, (the biting or grasping claws) and ·the second and third are also chelate, being furnished with small forceps. The abdomen is well developed · and there is. a strong fan~ like tail. Since the crayfish in P - PODOBRANC~ habit fresh water and lob sters salt water, there is not generally much chance of the two being confused. However, it is possible that they might ovedap in estuarine waters (one large crayfish caught recently in one of the mouths of the Fraser river was considered by several people to be a lobster escaped from the Lasqudi island planting), so it is wo,rth while enumerat Fig. 7. Fourth pereiopod of the Crayfish: Note podo branch, attached ito epipodite throughout its length. ing the principal distinguish Fig. 8. Fourth pereiopod of the Atlantic Lobster. ing features. Lobsters in Note podobranch att,.ched .to. epipodite at base, but general grow to a larger otherwise separate from it. size than crayfishes (note the difference · in size be tween the lobster . in figures 4 and 5 and the Cl'ayfish in figure 3) but this is not a .reliable means of identification, since a . fair-sized crayfish could easily be as big as a. small lobster. The large chelae provide a more reliable guide to. identification, for the Atlantic lobste1r has one of these adapted for seizing, holding .and tearing the prey, and the other, which is larger and more rounded, serves the function of crnshing the food. (The difference in appearance between these two claws can be seen in figure 5). In the crayfish (figure 3) both claws are alike inshape and resemble the more primitive,· cutting claw of the lobster, except that they show a distinct tapering towards the ends. There may or may not be an appreciable differ ence in size between the two claws of the crayfish. Another, and very reliable distinguishing point between lobste1·s and crayfish is the. relation of the podobranchs (the lowest of the three series of gills) to the epipodites (the projections o.f the bas.al joints) of. the first four pereiopods or walking legs. In the crayfish the podobranch is united throughout its length with the epipoclite (figure 7), while in the lobster the podobrai1ch, though united to the epipodite at its base, 1s separate from it for the rest of its length 16 (figure 8). This difference may be seen in the animals by raising the flap of the carapace which covers the gill chamber above the walking legs. Crabs are too well known and too distinct to be wrongly identified but there is one other group which is sometimes confused with lobsters. These are the ghost shrimps or mud shrimps, Callianassa and Upogebia. Shrimp-like in general appearance, they vary in size from about lf to 3 inches from tip of rostrum to tip of tail, and they have a well developed abdomen held straight out. Callianassa, particularly, is confused with young lobsters be cause it possesses a single very large and well developed chela, formed from the first pereiopod of one side, its corresponding opposite member being also chelate but very much smaller (see figure 6), while in U pogebia the larg·e chelae are of approximately the same size, the forceps, however, being much less we'll developed. Apart from any anatomical points, the easiest way of distinguishing ghost or mud shrimps from young lobsters is the fact that the former burrow in wet sand and mud in the intertidal zones, while young lobsters of comparable size swim in relatively deep water. Pacific Biological Station J. S. T. Gibson PROBABLE CAUSE OF THE BROWNING OF CERTAIN HEAT-PROCESSED FISH PRODUCTS In previous issues of this series of Progress Reports (No. 64, p. 57; No. 66, p. 17 and No. 68, p. 52) the conditions re~ponsible for rancidity develop ment in fish flesh were described and certain control measures were outlined. Rancidity in fish products is frequently accompanied by visible alterations in the flesh, such as the yellowing (rusting) of exposed fat, bleaching of red astacin pigments and a brown or yellow discoloration of the more fatty portions of white-fleshed fish. Another, and entirely different, change involving discolorations of fish products occurs and this is briefly discussed herewith. During the war when dehydrated and other foods were, of necessity, stored under very adverse conditions as regards temperature and humidity, considerable deterioration in quality often resulted. Food technologists who studied the cause of this loss of quality soon concluded that the so called "Maillard," "Non-Enzymic Browning" or "Sugar Protein" reaction was frequently implicated. This. reaction is now generally referred to as the Industrial Browning Reaction,· or, more simply, as the Browning Re action. It was discovered in 1912 by Maillard, a Frenchman, who found that if watery solutions of a "reducing" sugar such as ordinary corn sugar (glucose) and a pure amino acid (protein breakdown product) were heated they became progressively browner and assumed a caramel and later a bitter flavour. In recent years experiments on foods have shown that the reaction in dehydrated products such as desiccated cocoanut, dried vegetables and powdered eggs is favoured by high storage temperatures and by moisture. The only known control measures are: (1) removal of one or both of the reacting substances, as by removal of reducing sugars through leaching or fermentation, (2) addition of sulphur dioxide or similar 17 substances which liberate sulphur dioxide, as by the "sulphuring" of dried vegetables or fruits, and (3) storing dried products which have only a very low moisture content. The Browning Reaction affects a great variety of foods including dehydrated eggs, milk. and vegetables, coffee, and similar products, and it appears that fish does not offer an exception. Experiments have, therefore, been initiated at this Station in order to determine how this reaction may affect fish products and what practical control methods might be applied. It has long been known that during canning the white flesh of certain species of fish such as cod, haddock, lingcod, red cod, and halibut, assumes a more or less pronounced brown discoloration, and that this is frequently accompanied by a noticeable caramelized or acrid odour and flavour. Like wise tomato sauce in canned herring may become quite brown during processing and dehydrated fish may deteriorate during storage. There seems little doubt that the Browning Reaction is often responsible for these alterations and the following experiments support this contention. · When fish flesh such as that of lingco 18 EXPERIMENTS ON THE CANNING. OF FRESHWATER FISH Freshwatei;- fish from the interior provinces of Canada has been home canned in sealers or tinplate containers for many years, but these pro cessings were for the most part on a s:trlall scale and restricted in individual operations in the home. From a scientific viewpoint procurable records of these procedures or methods and the quality of the resultant products have revealed little information. Inquiries received at this Statfon regarding the canning of freshwater fish date back a number of years and show a sustained interest in the prospect of industrial development of fish canning. This Station offered advice on the canning problems, but was unable to undertake many €:xperi• mental investigations until recently. In Manitoba, funds were provided in 1939 at the University of Mani toba for a study on "The Commercial and Home~Canning Possibilities of Mullets". Laboratory space was provided at the Armstrong Girnli Fisheries Limited at vVinnipegosis, and the experiment was under the supervision of the Department of Horne Economics, University of Manitoba. Samples of the canned product were examined by the staff of this Station. The writer was unable to obtain information regarding any increase .in home canning occasioned by this investigation, and no significant commercial undertaking resulted. The outbreak of war may have affected plans for commercial development. In Alberta, according to the Report of the Royal .Commission on the Fisheries of .Saskatchewan (1947), one commercial venture into the canning of freshwater fish took place: "In 1921, 10 cases of whitefish and 625 cases of trout were canned on Lake' Athabaska but operations were abandoned because of the difficulty in obtaining a ri:iarketjor the product." The Province of Saskatchewan, accepting the following advice of the above Report: "Before any commercial project is attempted, experimental . work should .be carried out by qualified scientists and careful consideration given to the economic factors involved", built a pilot plant and undertook experimental work under the guidance and with the assistance of this .Station. Eighty-three initial canning experiments have revealed numerous difficulties and problems which can only be solved by research. The progress made to date is encouraging and indicates a possible future for a canning industry despite some adverse criticism. Some of the criticism was occasion ed by a lack of understanding of the. fundamental principles in a research problem. It is not generally understood that as much, if not more, can be learned from unfavourable as from favourable results. Due consideration must be given to the nature of the. material to be canned, but the quality of the finished product depends primarily on the freshness of the raw material. This is particularly true with fish. Off odours including hydrogen sulphide, brownish discolouration throughout the product during processing or storage, and some can corrosion have been traced to staleness of the fish before canning. Though freshness is essential, it is not the only factor affecting flavour, colour and texture of the canned product. "Whitefish from various lakes when canned revealed flavour and texture characteristic of that species of fish from the specific lake source. Tullibee from one lake showed marked flavour difference with the seasons. Mullets caught in the adjoining river showed a flavour quite distinctly different from the lake-caught mullets. 19 commercial consignments of frozen fish for the experiments. The second shipment was from the plant of the Prince Rupert Fishermen's Co-Opera tive Association, a member of the Federation. The first road test, from New Westminster, B.C. to Montreal, P.Q., compared two refrigerant mixtures in standard overhead cars of the Canadian Pacifi)c Railiway. One car was refrigerated by a mixture of 25 parts of NaCl to 100 parts of crushed ice by weight; the other by a mixture of 25 parts of NaCl plus 12.5 parts of NH4N03 to 100 parts of crushed ice by weight. The second road test, from Prince Rupert, B.C. to Montreal, compared similar mixtures in two Canadian National Railway refrigerator cars; in one car the refrigerant was added in the proportion of 30 parts of NaCl to 100 of ice; in the other, 30 parts of NaCl plus 15 of NH4NOa to 100 of ice. During the tests, temperatures of outside air, inside air, product, and refrigerant mixtures were determined by electrical thermometers. The centre-top and centre-bottom temperatures of insi1e air were determined also by the liquidometers which are standard equipment on Canadian refrigerator cars. A detailed report of these tests is being published by the Natioml Research Council. In summary, the results indicate that the added NH4NOa lowers the average air and product temperatures by about four to five Fahrenheit degrees. This improvement in temperature was less than anticipated, but during the tests it was observed that the temperatures of the bunkers containing NH4 N03 fluctuated appreciably between icing times. Immediately after icing the temperature reached a low point of about - 16°F. but rose steadily from this temperature until the next icing. The resultant average bunker temper ature was about-'- l:0°F. Rather than a fluctuating temperature, a constant temperature of about -16°F. had been expected. It was believed that such a bunker temperature would cause a lowering of about ten degrees in the refrigerator car. In an attempt to determine the cause of the fluctuation in temperature the bunker solutions were sampled at intervals throughout th_e second test. Chemical analyses of these samples showed that the temperature had fluctuated inversely with the NR1N03 concentration. High NH4NOa con centr.ation caused the low temperatures. Immediately after re-icing, the NH4 NOa concentration was ·much higher than the percentag-e of NH4NOa added in the refrigerant mixture, whereas before re-icing the NH4NOa concentration was lower than that percentage. Since the NH4N03 concen tration was very low before re-icing, the bunker temperature was relatively high. The fact that the concentration of NH4N03 before re-icing is lower than the proportion added with the ice may be explained by considering what occurs between icings. On the addition of the refrigerating mixture to the bunkers, a considerable portion of the ice melts to absorb the heat which must be removed in lowering the temperature of the mixture to - 16°F. This. meltage; which has a very high concentration of the highly soluble NH4N03, escapes through the overflow after its concentration has been somewhat reduced by the old brine. V\Then the train starts to move, 24 the agitation causes further expulsion of brine having a high NH4N0a concentration. Hence, considerable quantities of high concentration brine are expelled and subsequent dilution by ice meltage reduces the concentra tion below that of the added mixture. These results were corroborated with laboratory apparatus, and with the same apparatus an attempt is being made to find the required concen trations of NH4N03 and NaCl to maintain the temperature constant. In preliminary tests, not only has a constant temperature.been closely approach ed, but also the temperature has been significantly lowered. Our laboratory model which appears to simulate full-scale bunker operation has induced a low temperature of -24°F. and an average temperature of -21°F. If a similar temperature can be maintained within the refrigerator car bunkers,' an average temperature of + 5°F. could be expected throughout the load. If after a more thorough laboratory investigation the method·· still appears feasible, we hope that a road test will be arranged in the coming summer. Pacific Fisheries Exp.erimental Station D. H. Taylor J. S. M. Harrison Pacific Sub-Executive Committee of the Fisheries Research Board of Canada A News Item on page 72 of issue No. 73 of these Progress Reports outlined the functions of the Pacific Sub-Executive Committee elected annually by the Fisheries Research Board of Canada to assist in guiding the operation of the Board's two western Stations. This Committee met in Ottawa just prior to the annual meetings of the Board held there during January 2-6 this year, and later reported to the Board. Towards the close of the annual meetings two recently appointed members of the Board, Mr. K. F. Harding, General Manager of the Prince Rupert Fishermen's Co-operative Association, Prince Rupert, British Col umbia, and Professor I. M. Fraser of the College of EngineeTing, University of Saskatchewan, Saskatoon, Saskatchewan, were elected by the Board as new inembers of the Pacific Sub-Executive Committee. Mr. R. E. Walker of the B. C. Packers Limited, Vancouver, and Dr. W. A. Clemens of the Department of Zoology, University of British Columbia, Vancouver, were re-elected as members of the Committee, the former as Chairman. Dr. R. E. Foerster, Director of the Pacific Bi:ological Station, Nanaimo, British Columbia, was re-appointed to act as Secretary. 25 A NOTE ON NEW EQUIPMENT FOR DETERMINATION OF WATER IN FISHERY PRODUCTS Recently at this Station an electronic instrument for the determination 'of water in variotts materials was built. The details of its construction will be described elsewhere, but it is considered of interest here to indicate its application to fishery products. Determination of water by this method is applieable .to samples of almost any material (strong caustic solutions being an exception). Any materials such as fresh, dried, salted, or smoked fish, fish meal and fish oil may be used provided a small enough representative sample is taken· to fall within the range of the method. · The determination of moisture has always been a problem. The amount of water in any substance is important for a number of reasons. One is the control of purity or quality. Another is the fact that a purchaser objects to buying water when he is of the opinion that he is buying a more valuable commodity. Also, the accurate determin<).tion of water in some substances has great imp_ortance from a theoretical point of view. In the past, many methods 'for this determination have been devised, some very simple, some more complex, some quite ingenious. The simplest and most common is that of drying the material, usually at an elevated temperature, and determining the loss of weight. While this is an excellent method for the determination of water in some material, e.g., common salt, it falls down in some other cases, e.g., fish meal; and cannot be used at all in others, .e.g., liquids with low boiling points. The reasons why the oven drying method is not ideal for substances like fish meal are several. The first objection is that, when meal is heated, ·other substances besides water may be driven off; for example, amines and some oxidation products of the oils. This means a loss in weight .which is not due to water. The second objection is that certain constituents may undergo oxidati.on and the material gains weight. A third objection is that under elevated temperatures some complex organic constituent may tend to break down into constituents of lower molecular weight, some of which are volatile, and the material again loses weight which is not due to water. The fourth objection to the oven drying method is the. time ne•cessary for the determination. As a result of all these difficulties, moisture determination in fish meals, and like materials, is usually a highly empirical procedure. Because of all these objections great interest and much scientific investigation has centered around the development, a fow years ago, of a purely chemical method for moisture .determination. It was discovered by Karl Fischer who proposed the use:1 of a reagent made up of methyl alcohol, sulphur dioxide, pyridine and iodine. This mixture reacts quantitatively with water. Fischer used the reagent as its own indicator (it is yellow when an excess of wateT is present and brown when the water is all used up) but since the colour change is not abrupt, this alone was not found to be altogether satisfactory. Because of the versatility of the method, how ever, considerable work has been done to detect the end point with greater 26 prec1s10n. Probably the best method is by use of a vacuum tube voltmeter which measures the ionization potential of the reactants in a solution of methanol or other inert solvent. For purposes of comparison, .the moisture in six representative samples of the same :fish meal recently was determined in these laboratories Ly the two different methods as indicated in the accompanying table. In the oven drying method, three small (2-gram) samples were wdghed out accurately and dried in an oven .at 100-110°C. (212-230°F.) for 5 hours. At the end of this tiine they were cooled in ·a desiccator and weighed. Because the deviations from the mean ·weight were large on this weighing, they were dried for another 4 hours. r In the titration method, three 2-gram samples were weighed out accurately and each was coveTed with a known quantity (100 ml.) of a mixture of equal parts of chloroform and methyl alcohol containing only 0.05% of water. These were let stand in an incubator at 37°C. (98°F.) for 2 hours to assure complete extraction of the water from ·the meal. The samples were then titrated directly with the-reagent. Oven Drying Method Per cent Per cent water deviation found from inean* 7.68 0.52 7.67 0.39 7.58 0.79 *Mean=7.64 Approximate time for com1)lete analysis: Si'! hours Titr,ation Method Per cent Per cent water· deviation found from mean* 7.90 0.04 7.90 0.04 7.89 0.09 *Mean=7.90 Approximate time for complete analysis: 1 hour. Duiccat.or .Method l'er cent Per cent water deviation found from m can* 7.54 0.40 7.50 0.13 7.49 0.27 *Mean=7.51 Time· for determination of maximum drying: 15 days. (less for an approximate value) New equipment for determination of wate·r -·------~------in fishery produc.ts by the titration method. ------·------~-----=-.::.._-::::·_·===------= 27 In the third method 2~grq,m sarnples were placed over fresh phosphoric anhydride, a powerful drying reagent; in an evacuated desiccator. Periodic weighings. over a 15-day period showed that this length of drying time was necessary to achieve the maximum removal of water from the samples. Hence. this method woul.cl be impntctical for commercial determination of moisture in fish meal, although .it is. of use in other types of determin::ttions where a shorter drying period is sufficient. The means of these three sets of determinations differ less than 0.5%. The precision of the titr?-tion method is greater .than that of_ the other two methods, as indicated by the maximum per cent deviations from the means: 0.09 for the titration method, 0.40 for the desiccation method, and 0.79 for the oven drying method. The speed of the titration method far surpasses that of the other methods, being 5i times faster than oven drying, and a great many times faster than the desiccator method. In view of these facts :md also because· the titration method probably gives a truer estimate of the _actual water content, it is the writer's opinion that this method is most suitable for determination of water in fish meal. Pacific Fisheries Experimental Statioii Norman E. Cooke Herring Investigation. Activities During the latter part of February and in March, herring investigators of the Pacific Biological Station will undertake their annual tagging and spawning ground survey expeditions. The "B. C. 'Pride," Captain B .. Skartveit, loaned by Nelson Bros. Fisheries Ltd., left for the west coast of Vancouver island on Febr;ua'ry 16, with Mr. A. G. Paul and Mr. J. W. Clark on board. This vessel will work for the first few clays in Barkley sound and will then head for the Quatsino sound area in an effort to cover spawning~ which usually occur there before the first of March. As soon as available, a second vessel, the "Great Northern 3," loanedby Francis Millerd & Co. Ltd., Captain A. Norman, and in charge of Mr., J. C. Stevenson assisted by Mr. T. H. Glover, will head for the southei;:n areas of the west coast of Van couver island. Mr. John Gibson will \tccon}Pany this expedition in order to photograph herring spawning grounds and egg depositions on V<:Lri.otts types of vegetation. A third vessel, the "'Pacific Sttnset," loaned by. the Canadian Fishing Co. Ltd., Captain R. Hirst o.f the.. Station Staff, left ..the Station aoout Mcttch 1-With Mr. J. A. La11igan and Mr.. J. H. Larkman on board. This vessel will cover the Strait ·of Georgia spawning grounds and will later join the other. two vessels on the west coast of Vanco11ver island. Dr. A. L. Tester is accompanying the third vessel and. will direct the operations of the other two by radio telephone. There are indications that spawnin.g wiH be relatively early thisyeai-. Already several spawnings have taken P;b.ce in Barkley sound, and fish have been reported in Matilda inlet and Ta,.hsis inlet. This infor111atio11 is gf particular interest in view of the latge catches which were made on west coast of Vancouver ishLlld fishing grottnds during the 1946-47 and 1947-48 seasons. 28