Bulletin No. 128

A hydraulic escalator harvester

By J. S. MacPHAIL Research Board of Canada Biological Station, St. A.ndrews, N.B.

PUBLISHED BY THE FISHERIES RESEARCH

BOARD OF CANADA UNDER THE CONTROL OF

THE HONOURABLE THE MINISTER OF FISHERIES W 1961 Lr-[I ====;-L,ll'-�TTA A, �II �ce: 50 cents

u ��------� Bulletin No. 123

A hydraulic escalator shellfish harvester

By J. S. MacPHAIL Fisheries Research Board of Canada Biological Station, St. Andrews, N.B.

PUBL ISH E D BY THE FISHERIES RESEARCH BOARD OF CANADA UNDER THE CON TROL OF THE HONOURABLE THE MINISTER OF FISHERIES OTTAWA, 1961

96488-2-1 W. E. RICKER N. M. CARTER Editors

ROGER DUHAMEL, F.R.S.C. QUEEN'S PRINTER AND CONTROLLER OF STATIONERY OTTAWA,1961

Price: 50 cents Cat. No. Fs 94-128

(ii) BULLETINS OF THE FISHERIES RESEARCH BOARD OF CANADA are published from time to time to present popular and scientific information concerning fishes and some other aquatic animals; their environment and the biology of their stocks; means of capture; and the handling, processing and utilizing of fish and products. In addition, the Board publishes the following:

AN ANNUAL REPORT of the work carried· on under the direction of the Board.

THE JOURNAL OF THE FISHERIES RESEARCH BOARD OF CANADA, containing the results of scientific investigations.

ATLANTIC PROGRESS REPORTS, consisting of brief articles on investigations at the Atlantic stations of the Board.

PACIFIC PROGRESS REPORTS, consisting of brief articles on investigations at the Pacific stations of the Board. The price of this Bulletin is $0.50 (Canadian funds, postpaid). Orders should be addressed to the Queen's Printer, Ottawa, Canada. Remittance made payable to the Receiver General of Canada should accompany the order. All publications of the Fisheries Research Board of Canada still in print are available for purchase from the Queen's Printer. Bulletin No. 110 is an index and list of publications of the Board to the end of 1954 and is priced at 75 cents per copy postpaid. Circular No. 58, available upon request from the Fisheries Research Board, Ottawa, lists its publi:ations during 1955-1960. For a listing of recent issues of the above publications see inside of back cover.

(iii) 96488-2-1!

CONTENTS

PAGE

INTRODUCTION AND ACKNOWLEDGMENTS...... 1

DESCRIPTION OF THE ESCALATOR HARVESTER...... 3

I. Boat...... 3 II. Digging equipment...... 3

OPERATION...... 12

CONSTRUCTION COSTS...... 13

DEVELOPMENT HISTORY ...... 14

PERFORMANCE ...... 18

1. rate...... 18

2. Limiting depths ...... 19

3. Fishing efficiency...... 19

4. Scattering of and damage to non-marketable stocks ...... 20

DEMONSTRATIONS AND ASSISTANCE TO INDUSTRY ...... • 22

SUMMARY AND PROSPECTS...... 23

REFERENCES ...... 24

(V) INTRODUCTION AND ACKNOWLEDGMENTS

The conventional hack, quahaug rake, rake, and oyster tongs have been used for harvesting shellfish in the Maritime Provinces for the past 100 years. These instruments are not only inefficient but by their primitive nature require a great deal of costly manual effort. The present abundance of shellfish stocksand their market value do not make the drudgery and low returns of fishing with these implements attractive to present-day fishermen who are accustomed to various degrees of mechanization in capturing other kinds of products. Consequently, many fishermen who formerly augmented their incomes by fishing shellfish have turned to other occupations. Besides this general deterioration of interest in the inshore shellfish industries, our soft-shell clam production has dropped from its 1950 peak of 23 million pounds (weight as landed in shell) to 21 million in 1959. This drop has been caused, at least in part, by the wastefulness of harvesting with clam hacks which kill about 50% of the small left behind in the soil. Under these circumstances the Department of Fisheries and the Fisheries Research Board began their re-examination of shellfish harvesting methods and particularly their search for a more efficient and less destructive method of fishing soft-shell clams. The hope was that its use would help the clam stocks to recover some of their former abundance.

We knew that in Maryland, U.S.A., in 1954, a clam , Mr. Fletcher Hanks, Jr., had invented and patented a mechanized clam digger for hydraulic harvesting of the permanently submerged clam beds in Chesapeake Bay. The principle of hydraulic fishing is not new. It was originally applied to shellfish dredges more than 30 years ago. The Fisheries Research Board of Canada Biological Station, St. Andrews, N. B., used a hydraulic dredge for its initial survey of our bar clam resources 111 1946-48 (Medcof and MacPhail, 1955). Similar dredges are still used for fishing bar clams and ocean quahaugs in water depths of up to 125 feet (MacPhail and Medcof, 1959). Besides this. many hydraulic devices, incorporating the use of force and suction pumps, have been built in the United States for harvesting shellfish. The success of these ventures has varied and it is likely that some more or less resemble the Chesapeake Bay type of harvester described here.

In 1955, we built a mechanized digger at the Biological Station, St. Andrews, N.B., patterned after those we saw in operation that year in Chesapeake Bay when we visited Mr. J. H. Manning at the Chesapeake Biological Laboratory. Our model was modified for harvesting intertidal flats which produce most of our soft-shell clams (Dickie and MacPhail, 1957). By 1957, after many altera­ tions, the machine was fishing soft-shell clams in a very satisfactory manner.

1 This digger, often referred to now as an escalator harvester, was built originally to fish only soft-shell clams. But it soon appeared from our trials that with modifications it could be used to fish other species of shellfish. This en­ couraged us to explore its wider usefulness. Exper;mental work was continued until autumn 1959. The harvester has proven to be an extremely versatile machine, gathering the four commercially important shallow-water species­ soft-shell clams, bar clams, quahaugs, and -with a high degree of effi­ ciency and at profitable rates for its operators. We believe that it will eventually prove more useful on our coast for oyster and quahaug fishing than for soft-shell clam fishing.

The Industrial Development Service of the Department of Fisheries pro­ vided funds to build the boat and harvester and to operate it. They engaged a skipper for approximately 6 months each year and a deckhand when necessary. The Department's Conservation and Development Service aSSIsted by supplying a Fisheries Guardian at Clam Harbour, N.S., where much of the experimental work was carried out and where the boat and equipment were stored during the winter months. The work was conducted under the joint supervision of Drs. J. C. Medcof and L. M. Dickie. Ideas concerning modification of the harvester were contributed by all persons involved in this experimental work. The boat skippers, Messrs. A. W. Holt and E. C. Durkee, with their general fishing knowledge and by their conscientious efforts added much to the success of these trials. We are particularly indebted to Mr. H. Y. Brownrigg for working out the many details of escalator construction and boat rigging and for his personal supervision of this portion of the work.

2 DESCR IPTION OF THE ESCALATOR HARVESTER

I. BOAT The boat (Fig. 1) from which the harvester was operated is 36 feet in length with a l2-foot beam and 2-foot draught. It was designed specifically for mecha­ nized shellfish digging in shallow water over intertidal flats. It has an ll-foot fo'c'sle, a 22-foot, self-bailing cockpit and a 3-foot stern deck. It is powered with a 6-cylinder, lOS-horsepower (HP) gasoline engine turning, with direct drive, a 14 X 8 inch propeller.

FIGURE 1. Perspective drawing of 36-foot M.B. Cyprina from the starboard, showing escalator harvester equipped with the oyster scoop. (Drawing by Alan McIver).

I I. DIGGING EQUIPMENT Basically the digging equipment consists of a scoop which is forced ahead through the sea bottom by the boat. In front of the scoop is a manifold with water jets to loosen the soil in its path. Behind the scoop is a conveyor with an endless belt which brings the shellfish to the surface.

(1) FORCE PUMP ASSEMBLY. A 4-cylinder, S6-HP, air-cooled gasoline engine mounted about amidships provides power for a centrifugal force pump with a capacity of 750 gallons per minute (gal./min.) at 40 pound's pressure per square inch. A 6-inch diameter, wire-reinforced suction hose containing a foot valve is suspended over the port side while the harvester is in operation. This intake hose

3 96488-2-2 is hoisted to the washboard when the digger is not in use. A 4-inch-diameter discharge hose leads from the pump to the manifold on the digging scoop on the starboard side of the boat. The pump is provided with a priming device operated by the pump engine exhaust.

(2) ScooP. The digging scoop (Fig. 2) which is fastened to the forward end of the conveyor frame is of No. 12 gauge sheet iron. It is in two sections hinged together so that the leading portion travels parallel to the bottom regardless of

9

FIGURE 2. Digging scoop. (Drawing by P. W. G. McMullon). 1. i" hoist bale. 2. i" shackle welded to flat-iron support. 3. 1i " X H" X 1" X 291" angle-iron with I" tow shackle welded at centre. 4. 1i " X i" X 8" flat-iron brace. 5. 1i " X i" X 25" flat-iron support bevelled on leading edge. 6. 1" chain for adjusting angle between two portions of scoop. 7. li" X H" X 1" X 30" angle-iron. 8. Corner filler. 9. Three 12" liT" hinges. 10. i" holes for fastening shoe to dig at various depths.

4 the depth of water in which digging takes place. A manifold (Fig. 3) fastened crosswise on the forward end of the scoop contains 8 nozzles such as are used for washing gravel. These are of machined bronze and each delivers 75 gal./min. at 40 pounds pressure per square inch in a powerful flat spray. There are also two streams of water directed backwards towards the mouth of the conveyor through longer nozzles (blow-backs) of galvanized iron pipe that have been bent to shape.

6

150· 3

FIGURE 3. Manifold. (Drawing by R. A. Greenlaw).

1. 4" diameter male fire hose coupling. 2. 4" diameter black iron pipe welded to coupling. 3. 4" diameter black iron pipe, 331" long with !" flat iron ends containing 1" threaded hole in centre. 4. 1" X I" reducing couplings welded to manifold for I" X 24" galvanized pipe blow-backs. 5. I" X !" reducing coupling for stand pipe on escalator frame. 6. 1i" V-jet flat spray nozzle. 7. 1 i" coupling ground to taper and welded to manifold. 8. 1i" X !" X 2" adjustment lug.

Inset: 1. Fire hose coupling. 2. Blow-back. 3. Nozzle. 4. Adjustment lug.

5 96488-2-2! Adjustable shoes (Fig. 4) bolted to the outer sides of the scoop ride along on the surface of the bottom. By being pre-set, these determine the depth to which the scoop will dig. A tow warp is fastened to the cross-member on the forward portion of the scoop and passes through a block on the "A" frame on the fo'c'sle deck, back to a cleat on the starboard washboard.

�6 I 1---1

FIGURE 4. Shoe for scoop. (Drawing by R. A. Greenlaw). 1. 5" X tf! X 3'1 0" flat-iron. 2. 4" X ttl X 3'5" flat-iron. 3. 2" X 2" X ttl angle-iron. 4. 9!" X 6" X !" flat-iron welded to angle-iron and containing !" holes for manifold bolts. 5. 1" X -t,f' X 12!" flat-iron with 5" X i" slot for manifold adjustment. 6. 4" X 2" X 1 r ' tapered to iff spacers for fitting to scoop. 7. !" bolts for fastening shoe to scoop. 8. Width between ! iron plates 2'10".

(3) CONVEYOR. The conveyor frame (Fig. 5, 6 & 7) IS built from 1t-inch Douglas fir. It is 20 feet long, 21i inches wide and 18 inches deep a t the scoop end and tapers to 7 inches about midway along its length. Running lengthwise, and 6 inches apart, along the inner surface of each side of the frame are two strips of angle-iron. They are bolted on the inner faces of the conveyor frame and serve as guides and supports for the conveyor belt. For additional strength, the frame is strapped at each end and at the centre with a rectangle of angle­ iron. The top of the frame is covered WIth galvanized screening from the scoop to a point about midway along the frame.

6 ""-l

FIGURE 5. Escalator-front section. (Drawing by R. A. Greenlaw).

1. Escalator frame 18i" deep 1 i" hardwood. 12. 1!" X H" X i" X 211" angle-iron. 2. Heavy gauge galvanized iron 1!" wide folded to take end of screen. 13. !" galvanized pipe attached to centre outlet manifold with £" plas- 3. i" galvanized wire mesh. tic pipe-clears trash from belt. 4. Hardwood wire mesh screen cover. 14. 2" X !" X 7" flat-iron to hold axle no. 1 roller. 5. 1!" X i" X 24t;" flat-iron. 15. £/1 pipe spacer. 6. Distance between escalator sides 19" (inside). 7. 1!" X l!" X i" X 25 £" angle-iron. 16. No. 1 roller 7!" forward of no. 2 roller. 8. Hardwood 4" X 1 £" X 25" to hold axle no. 2 roller. 17. No. 2 roller, tops of rollers level with track. 9. 2" X 2" X 6'6" hardwood guard fenders. 18. 2" X 2" X i" X 17'1" angle-iron, upper track fastened to hardwood 10. 2" X 2" X i" X 16'5" angle-iron return track. with ·N' flathead stove bolts. 11. Hardwood sill 2" X 3" notched r' deep 2!" from ends. 19. Wood cut away to accommodate rollers. 2

00

FIGURE 6. Escalator-mid section. (Drawing by R. A. Greenlaw). 1. t" galvanized wire mesh. 2. Flat iron 1 ¥' X t" X24t" long. 3. Upper portion escalator frame 8' X 7" X 1k" hardwood. 4. 1!" Xl!" X t" X 21" angle-iron. 5. a" X H" X t" X 211" angle-iron. 6. Spacer 1k" thick. 7. Hardwood sill same as front end. 8. 2" X 2" X t" angle-iron return track. 9. Escalator frame 7" Xli" hardwood. 10. 2" X 2" X t" angle-iron-upper track. 11. 2" X2" hardwood braces and fenders. 12. 2" X 2" X 6'6" hardwood braces and fenders. 13. Hardwood stop removable platform. 14. H" X 1!" X t" X 21t" angle-iron with !" hoist shackle. 15. 1!" Xl!" X t" X 20" angle-iron. 16. Same as no. 14. 17. Spacer same as no. 6. 18. Hardwood sill same as no. 7. 19. 1" X 1" flat wire conveyor belt. 7

2.

1/ /2 e,

16

15

FIGURE 7. Escalator-rear section. (Drawing by R. A. Greenlaw).

1. Platform for starting engine. 2. Hardwood engine mount, tapered 4" to 2". 3. Engine bolt mounts, with spacers. 4. Reduction gear, 5.5: 1. 5. 4t" pulley, i" wide groove. 6. B section V-link adjustable V-belting. 7. I" pillow bearings. 8. 3" X 4" X 8" X t" flat-iron. 9. I" shaft. 10. 9" pulley, i" wide groove. 11. 19-tooth sprocket, iff pitch. 12. Chain, iff pitch. 13. 76-tooth sprocket, iff pitch. 14. Galvanized iron guard. 15. Escalator frame, 20' overall. 16. 1i" X 8" X 21" hardwood bearing mount. 17. Ii" X i" spring steel clutch handle. 18. i" X i" X i" notched angle-iron. 19. i" U bolts. 20. Clutch shaft, i" iron. 21. Brass idler, 2" diameter. 22. 1 iff X 4" X 21" hardwood engine mount. 23. 2" X 2" X i" angle-iron IS" long slotted for adjustment of belt sprocket; I" pillow bearing underneath. 24. I" X I" flat wire conveyor belt. 25. 2" X 2" X i" angle-iron retnrn tracle 26. 2" X 2" X i" angle-iron top track.

9 Two types of conveyor belts have been used during fishing operations. One, which we have used in experimental work, is i-inch mesh woven wire 18 inches wide and rotates on three rollers (Fig. 8 & 9). The drive roller (not illustrated) has small teeth welded on it to engage with the mesh and rotate the belt. The other conveyor belt, which is used in , is flat wire with 1 X l­ inch mesh. It is driven by two sprockets mounted on the drive shaft (Fig. 10). The teeth of the sprockets engage with the links.

FIGURE 8. No. 1 roller. (Drawing by R. A. Greenlaw). 1. iff steel shaft fastened to escalator frame (does not turn). 2. r' bearing. 3. iff flat-iron welded to 2" galvanized pipe recessed on inside t" deep to fit 1 t" pipe. 4. 2" galvanized pipe 18!" long (distance between fiat-iron and plates). S. 1 t" galvanized pipe. 6. iff hole. 7. Grease nipple.

I

FIGURE 9. No.2 roller. (Drawing by R. A. Greenlaw). 1. I" steel shaft fastened to escalator frame (does not turn). 2. I" bearing. 3. iff fiat-iron 8" diameter turned to 6" diameter r' deep on inside face. 4. iff holes bored iff deep to fit No. 8 which are spot welded to end plates. S. t" deep recess to fit 2" pipe. 6. 2" galvanized pipe. 7. Grease nipple on 2" pipe. 8. iff iron rods 19" long to fit in i" deep holes in end plates, and spot welded to end plates. Roller 18!,' inside with 6" diameter.

10 FIGURE 10. Conveyor belt sprocket assembly. (Drawing by R. A. Greenlaw). 1. 1" rliameter steel shaft, 2. Drive end keyed to accommodate 76-tooth i" pitch sprocket. 3. 6" diameter cut tooth (or cast iron) 1S-tooth sprockets spaced on shaft to suit conveyor belt. 4. Idler pulley Si" diameter to support centre of conveyor belt.

Power for rotating the conveyor belt is supplied from a 2-HP, air-cooled gasoline engine with a 5.5: 1 reduction gear and is transmitted from a 4�-inch pulley with B-section V-link belts to a 9-inch pulley on a counter shaft. A chain drive from a 19-tooth sprocket with a i-inch pitch 011 the counter shaft turns a 76-tooth sprocket on the main shaft resulting in a total reduction of 44: 1 (Fig. 7). A small idler roller in the V-belt system is mounted on an adjustable arm attached to the conveyor frame (Fig. 7). This controls the tension of the V-belts and acts as a simple clutch permitting the conveyor belt to be stopped without shutting off the engine.

(4) RIGGING. Two booms on a mast which is stepped about amidships, immediately forward of the main engine, suspend the digger, by its forward and after ends, over the starboard side of the boat (Fig. 1). Since the starboard side must be clear of rigging to accommodate the digger. the mast is braced and stayed only on the port side. The harvester as a whole is raised and lowered by wire ropes with appropriate fair leads to two �·ton hand winches fastened to the mast. When not in use the harvester is swung inboard alld rests 011 the washboard.

11 OPERATION

To begin digging, the harvester is swung horizontally over the starboard rail. The forward end of the escalator with its digging scoop is lowered to the bottom, the pump engaged and the boat set in motion. The towing warp, fas­ tened to the scoop and the "A" frame on the boat, becomes taut and consequen­ tly the leading edges of the scoop exert a steady forward pressure on the soil. The actual digging of the bottom and shellfish is accomplished by the action of the water jets which are directed downwards and backwards. The shellfish, empty shells, soil and some rocks are washed into the mouth of the scoop where they are picked up by the rotating belt.

Normally the large-mesh belt is used and the marketable shellfish are picked manually from the belt. The under-size animals and debris are left on the belt to travel upward and fall over the after end of the escalator into the water. When fishing for seed stocks (I to it inches long), particularly for soft-shell clams, the small-mesh belt is used. At such times the entire catch is collected in baskets placed immediately under the after end of the conveyor belt. The seed stock is later separated from the debris by screening.

Except in heavy clay soils shellfish come up washed clean. This simplifies culling and sorting and generally makes an attractive looking catch.

12 CONSTRUCTION COSTS

The costs involved in building an escalator harvester and boat will vary from place to place and the figures shown in Table I will serve only as an indication or guide for those interested in this type of machine.

TABLE 1. Estimated costs, including materials and labour, for construction of escalator harvester and boat.

Boat-length 40 feet, beam 13 feet, draught 2! feet-native materi�ls-complete with gasoline engine, shaft and propeller ...... $4 ,500. 00 800 gal./min. @ 40 pounds per square inch centrifugal force pump complete with air-cooled gasoline engine, intake and discharge hoses ...... 2,500.00 Escalator harvester 30 feet long complete with scoop, conveyor belt and gasoline engine ...... 1,500. 00 Rigging and contingencies ...... 1,000.00

$9,500.00

We recommend a Cape Island type boat with shallow draught and a beam about one third its length. This provides for stability and a large cockpit for equipment and working space.

We also recommend a separate pump engine, since, to deliver the necessary water pressures and volumes, it is usually run at higher speeds than the main engine. However, experimental work has been done at Chesapeake Biological Laboratory, Solomons, Maryland, U.S.A., on a controllable pitch propeller for boats equipped with escalator harvesters. This enables one engine to serve both purposes and, besides making space available, it reduces fuel consumption by about 30% without sacrificing flexibili ty of operation (Manning and McIntosh, 1960).

13 DEVELOPMENT HISTORY

The escalator harvester was given its initial trials at Clam Harbour, N.S., during the summer of 1955. Mechanically it functioned satisfactorily. However, measurements of its efficiencyin harvesting soft-shell clams showed that although it captured over 90% of small clams (:£- to H inches in length) in its path, it gathered only about 50% of market-size clams (2 inches or greater). The scoop design was unsatisfactory in other ways. Often rocks or sand piled in the bottom of the scoop instead of washing through it onto the conveyor belt. This seemed responsible for the low efficiency in taking large clams which live at greater depths in the soiL

Another bad feature of the equipment was that the boat propeller dug deep trenches in the bottom soil particularly when operating in water less than 2� feet deep. Seed clams were washed from their burrows by the propeller blast and carried in vast numbers into these trenches and killed by over-crowding and smothering.

During the winter of 1955-56, the equipment and operation of the mechanized digger were critically examined and certain defects in our original design of the scoop and in the suspension of the harvester were revealed. Many modificatIOns were made and tested the following summer. A new digging scoop was constructed. The width was 30 inches instead of 36 and its length from the leading edge of the lower lip to the conveyor belt was 32 inches instead of 36. Besides this, the manifold of digging jets was moved from its fixed position on the front of the scoop to the front end of the adjustable shoes. This maintained the tips of the nozzles at the surface of the soil, regardless of the depth to which the scoop was digging. A 6-foot "A" frame was fastened horizontally on the fo'c'sle (Fig. 1) and this towed the scoop straight ahead from its centre. Pre­ viously the tow line passed through a ring on the stem of the boat at the waterline and this caused the scoop to tilt inwards.

Several propeller guards to prevent trenching were devised and tested in 1956. Finally a fiat, rectangular guard was adopted. It was 4 feet wide and 7 feet long and extended from the stern post to a point 4 feet beyond the transom. It reduced the cruising speed of the boat from about 6 to 4 knots but eliminated 3.11 trenching of the fiats. The boat could be grounded and the motor run at full throttle without noticeable disturbance to sandy soJ.

14 The results of the 1956 efficiency tests with the modified scoo;::> were unexpectedly good; the digger took virtually 100% of all sizes of clams in its path. Variations in pump or main engine speeds made little or no difference in the catch. However, when operating at the limit of the pump's capacity (250 gaL/min. at 20 pounds pressure) and digging to a depth of 14t inches in sandy soil, the digger moved through the bottom at the rate of 6 feet per minute. It was unable to dig eel-grass roots or work in clayey soils. This was a serious handicap for commercial operations.

During the winter of 1956-57 we reviewed all aspects of construction, equipment and operation of the digger and sought advice from Me E. E. Wheatley, Professor of Mechanical Engineering, University of New Brunswick, on certain changes that seemed desirable.

During the spring of 1957 more powerful engines were installed in the boat. The power of the propulsion engine was increased from 50 to 105 HP and of the pump engine from 25 to 56 HP. A larger pump (still in use) with a capacity of 750 gaL/min. at 40 pounds pressure was installed and the manifold was equipped with machined, flat-spray nozzles instead of iron pipe. These changes in the hydraulic assembly resulted in very powerful jets of water which enabled the machine to dig all types of soil in which shellfish are found including quite rocky ground. They also eliminated scoop clogging by shell and rock and increased the digging speed from 6 to 15 feet per minute with the scoop set to dig 14t inches deep.

A good portion of the summer of 1958 was devoted to studies of how the digger affects clam stocks and for a time the pump was used in deep-water fishing with a hydraulic dredge. But we did succeed in improving the propeller guard described earlier in this section. It was too cumbersome and had to be removed whenever the boat proceeded beyond sheltered waters. It was Mr. W. A. MacKay, engineer, of Construction Equipment Co., Ltd., Halifax, N.S., who des:gned and built the simple, compact guard shown in Fig. 11. It is bolted to the skeg so that the trailing edge is about t inch higher than the leading edge. When the propeller wash hits the guard it is directed upward and away from the bottom. This guard was very effective in protecting the bottom even in water 28 inches deep-just enough to float the boat. It reduced the boat speed only about 15% and the manceuverability proportionately. For this reason it can be installed and left in place indefinitely. With slight modifications this type of guard should be adaptable to the hull of any small boat used for escalator harvesting.

In the winter of 1958-59 a new scoop was designed and constructed for fishing oysters (Fig. 12). It incorporated many of the ideas we had developed

15 1 6"

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" 3 r is Plate " 7-I 2 fOrili ! 1 2f I, a" ·1· 9"----j

FIGURE 11. Propeller guard for M.B. Cyprina, designed to prevent trenching of bottom soil when working in shallow water. (Drawing by P. W. G. McMullon). Above: view from forward end; below: 3ide view.

from our own experience, particularly from oyster-fishing trials made with a modified clam digging scoop at Clam Harbour, N.S., in the autumn of 1958. The direction of the water jets was changed so they were parallel to the bottom to wash oysters into the scoop without digging into the soil as is necessary when fishing soft-shell clams, quahaugs, and bar clams. Besides this, the scoop was equipped with wheels and pneumatic tires to lessen damage to seed oysters lying on the surface of the soil and to prevent the lip of the scoop from disturbing bottom soil and plant life. The escalator and other equipment of the harvester remained unchanged from the previous year.

In the summer of 1959 efficiency tests were conducted in the Malpeque Bay area, P.E.I., on oysters planted at known densities. The scoop captured about 95% of the oysters of all sizes in its path. Extensive underwater observa­ tions of the ground worked over revealed no undesirable disturbance of bottom soil or plant life. The harvester moved at an average rate of 100 feet per minute which is equivalent to covering t acre of bottom per hour of continuous fishing.

16 10

:'IN '"

FIGURE 12. Oyster scoop. (Drawing by P. W. G. McMullon). L Spring loaded suspension-3" diameter pipe, containing coil spring and 1" eye bolt, welded to cross-member. 2. 2" X 2" X i" X 29:i" angle-iron bolted to sides of scoop. 3. i" chain for adjusting angle between two portions of scoop. 4. Bolt holes and axle slot for raising or lowering wheels. 5. 9" X 8" X i" plate welded to 1 i" steel axle 48" long. 6. 1!" Xl!" X i" X 30" angle-iron. 7. Corner filler. 8. :i" hinge bolt. 9. 670 X 15" car wheels with lignum vitae bearings. 10. 12" X 9" X f,j' plate drilled !" for various manifold settings. 11. 4" diameter manifold 34" long containing eight 1 i" diameter nozzles 14" overall length and bent midway at an angle of 140°. 12. i" tow chain.

17 PERFORMANCE

The escalator harvester, as we have modified it, brings up shellfish at sur- prising rates. This is attributable to three features in which it is almost unique: (a) It has a high efficiency in capturing all sizes of shellfish in its path. (b) It covers the ground at a rapid pace. (c) It fishes continuously as compared with manual tools and dredges which cease fishing when hoisted for emptying.

FISHING RATE The escalator harvester works through or over the bottom at 10 to 60 times the rate of a man with conventional hand implements and can therefore be used on grounds where shellfish populations are too sparse to encourage exploitation by present fishing methods. The production in bushels per hour shown in Table II is about the maximum that can be picked from the conveyor belt by two men, with the exception of bar clams where twice the volume could be handled. If two men are working the boat their catch per man per hour is 5 to 40 times (depending on the shellfish species) greater than with hand implements. Even if one half the value of the catch is consumed by operating expenses and amor­ tizing costs of the boat and harvester, the earnings per man would still be subs­ tantially greater than with hand tools.

TABLE I I. Fishing rates of escalator harvester compared with hand implements. Production

is in Imperial bushels per hour (1 bushel = 36.4 litres).

Escalator harvester Manual implements Density of shellfish Area fished Production Kind Production

number per square feet bushels bushels square foot per hour per hour per hour

Soft-shell clam ... 2 3,000 4 Clam hack Bar clam .. 0.16 4,500 10 Potato hoe" 1c Quahaug .. 0.67 7,500 10 Rake 5 1 Oyster. 0.33 15,000 10 Tongs 8

" Sight fishing for individual animals at periods of low tide.

However, the machine will fish much faster than shown in Table II. For example, on a public quahaug bed in Neguac, Miramichi Bay, N.B., the harvester gathered quahaugs at the rate of t bushel a minute but it required 5 men to pick these from the belt. They managed to do this but it was so tiring they were able to maintain the pace for only short periods of time and found it impossible to cull accurately for size. Similarly, in oyster fishing on a leased bed

18 in Malpeque Bay, P.E. I., it required 3 men to keep the belt clear of marketable oysters when they were coming up at a bushel a minute and these men, too, found it humanly impossible to maintain such work speeds. However, in fishing bedding-size oysters that are planted on relatively clean bottom, no culling is necessary and the fishing rate of the harvester need not be limited by the ability of the crew to keep the belt clear. The boat speed can be maintained at a maximum consistent with a high fishing efficiency and the oysters may be collected in scows or some such suitable carriers. From these figures on rate of catch it should not be assumed that the machine is overpowered. \Ve have learned from experience that for general work the capacity-pressure range of the pump unit now in use is barely above the minimum. There are few beds where less powerful assemblies would operate without clogging and other troubles. As already indicated, the engines can be set at whatever speed is required to keep volume of production at the level that can be handled by the crew.

LIMITING DEPTHS An escalator harvester will fish in water depths up to about one-fourth its total length. For instance, the overall length of the escalator harvester on M. B. Cyprina is 24 feet and it operates within a depth range of 2t to 6 feet. However, with larger boats longer escalators may be used. Fifty-foot boats with harvesters 35 to 40 feet in length are used in the Long Island, N.Y., quahaug fishery and these boats regularly fish depths of 10 to 12 feet. For fishing soft-shell clams from intertidal flats on the outer coast of Nova Scotia and in the Gulf of St. Lawrence an escalator with a depth range of 3 to 4 feet would be able to exploit most of the productive ground. However, for fishing permanently-submerged beds of shellfish like quahaugs, bar clams and oysters, escalators capable of fishing in depths of 8 to 10 feet would be desirable.

FISHING EFFICIENCY One of the important factors determining the value of any type of fishing­ gear is its fishing efficiency. By this we mean the proportion of shellfish it removes from its path as it passes over the bottom. A simple way of measuring fishing efficiency is to tag or mark shellfish and plant them in a carefully marked out bed at a known density. By fishing a known area of the bed with various implements the efficiency of each can be established by comparing the number of marked animals actually caught with the number known to have been present in the area fished. Table III shows the fishing efficiency of the common commercial implements used to harvest oysters and soft-shell clams, compared with the efficiency of the escalator harvester. Except for oyster tongs for fishing market-size oysters, the escalator harvester is unrivalled. Its ability to capture small-size shellfish makes it of special interest in oyster farming and in semi-culture operations such as seed quahaug relaying.

19 TABLE III. Fishing efficiency of oyster and soft-shell clam harvesting gear.

Oysters captured Soft-shell clams captured

Market Small Market Medium Small (more than (less than (3-4 inches) (2-3 inches) (1-2 inches) 2 inches) 2 inches)

% % % % %

Clam hack .. , ' 60

Tongs, , , . , , ' , , . , 90 60 40

Oyster drag, . , , . .... 30 23 13

Escalator harvester. , , 95+ 95+ 95+ 95+ 95+

When an oyster drag or clam hack is used the grounds have to be refished frequently because they miss so many marketable animals. But after an area is fished systematically with the harvester, refishing is unnecessary until the small animals in the area grow to cropping size. This feature makes the harvester adaptable to rotational fishing of grounds which is desirable in harvesting some speCIes.

4. SCATTERING OF AND DAMAGE TO NON-MARKETABLE STOCKS General observations made in the course of the development work indicated that there was little or no damage to non-marketable sizes of shellfish the escalator harvester left behind in the soil. This was expected for quahaugs, bar clams and oysters since they have strong, tough shells. The two former species are agile burrowers and are able to re-establish themselves quickly after distur­ bance. Oysters cannot move by their own efforts but normally land right-side up on the bottom when thrown into water. This is common practice in oyster farming and seems to do them no harm. We did not know what to expect for soft-shell clams, which are fragile, although we did know that small, uninjured clams are able to bury themselves in a comparatively short time. An experiment was carried out in Clam Harbour, N.S., to measure the damage the mechanized digger does to clams H to It inches in length (Medcof, 1960). It revealed interesting information about how the harvester scatters shellfish as well as about the clam damage it causes.

Formalin-killed, tagged clams were planted in plots on intertidal flats at known densities and at "normal" depths in the soil. The escalator harvester was then run through these plots in commercial digging fashion. Since the clams were dead, they did not burrow in the soil and breakage and scatter patterns as set up by currents from the digger were determined by inspecting the beach at the next low tide. Similar tests were carried out with marked, live clams in shallow and deep water and in loose and firm soils. The results were essentially the same

20 as with the tagged, dead clams. Scattering was remarkably slight. The harvester drops 90% of the under-size clams in the track behind the scoop only 50 to 75 feet from the point where they are dug. The rest fall on the undisturbed soil beside the track. Only 7 to 10% are damaged enough to prevent them from digging back into the soil in 3 hours. This means that the harvester kills only one fifth as many clams as clam hacks fishing the same soil.

In Maryland, escalator harvesting has been practised since 1950 for fishing permanently-submerged beds of soft-shell clams. Some areas produce an annual crop of clams, others more or less frequently, but none of the beds so fished has failed to be repopulated (Manning, 1957).

Escalator harvesters cannot be used in all the clam areas on our coast. Some beds are too small, irregular or rocky to be fished profitably. And the great rise and fall of tides in the Bay of Fundy makes escalator harvesting difficult and probably impractical. However, if harvesters were adopted in areas where they can be used, the yields per acre from these areas should be substantially increased.

21 DEMONSTRATIONS AND ASSISTANCE TO INDUSTRY

By 1957 the escalator harvester had been developed to its present efficient form for fishing soft-shell clams, quahaugs and bar clams. Its fishing qualities had been examined critically and it was felt that demonstrations to the and the Department of Fisheries were the next step in encouraging the use of this type of equipment.

During the summer of 1957 demonstrations were conducted in southern Prince Edward Island in Hillsborough Bay and Tryon Shoals and in 1\ew Brunswick on the northern shore of the Miramichi estuary. Many interested persons saw the digger in operation fishing bar clams, quahaugs and soft-shell clams. They were, without exception, impressed by the volume of shellfish this machine harvested even on grounds where shellfish were so scarce that manual fishing was not worth while.

In 1959, after the oyster scoop was perfected, oyster fishing demonstrations were carried out in Malpeque Bay, P.E.I. Fishermen and persons connected with the oyster industry were quick to recognize the possibilities of using the harvester in fishing for bedding-size oysters. They also saw it cleaning old oyster beds and fishing marketable oysters.

As a result of these various demonstrations escalator harvesters were built in New Brunswick in 1959, at Neguac and Shippegan. The Fisheries Research Board through its Biological Station at St. Andrews, N.B., assisted in the building of these machines by supplying detailed plans of the escalator and by visiting the builders and offering advice on materials and rigging. One of our staff also accompanied the owners of both new harvesters on their shakedown cruises and initial fishing trials. 'vVe are prepared to assist other builders in the same way.

22 SUMMARY AND PROSPECTS

Although the construction of the escalator harvester is described in consi­ derable detail in this report with illustrations and specifications, they should be considered as guides only. Many changes could likely be made in construction to enhance its fishing qualities or ease in handling. These innovations will come as industry builds and fishes these machines for the various species under the variety of conditions we have on our coast.

However, the machine as described here is extremely versatile, fishing the four commercially-important shellfish-soft-shell clams, bar clams, quahaugs and oysters-with high efficiency. It works over or through the bottom soil 10 to 60 times as fast as a man with hand tools, and it can be used on grounds where shellfish populations are too sparse to make fishing worth while with manual implements. It will fish in any type of soil in which shellfish are found, including areas that are quite rocky.

Water depths limit the scope of operations. Depths of 10 to 12 feet seem to be near maximum and these require escalators about 40 feet in length. However, in the Gulf of St. Lawrence there is a large bottom acreage available within this depth range where the 4 commercially important species are found.

We believe escalator harvesters will soon be common on our coast and will make shellfish fishing more attractive and remunerative for inshore fishermen. Many beds which are now unexploited or are exploited only slightly with hand implements will be fully and profitably fished. The slight damage the harvester does to soft-shell clam stocks recommends its use in preference to hand tools to encourage recovery of depleted stocks. Its greatest use, however, may be to oyster farming where its ability to recover bedding-size oysters from rearing grounds will reduce labour and material costs which should result in a substan­ tial expansion in our oyster farming industry.

23 REFERENCES

DICKIE, L. M., AND J. S. MACPHAIL. 1957. An experimental mechanical shellfish-digger. Fish. Res. Bd. Canada, Atlantic Prog. Rept., No. 66, pp. 3-9.

MACPHAIL, J. S., AND J. C. MEDCOF. 1959. Ocean quahaug explorations. Canadian Dept. Fisheries, Trade News,ll(12): 3-6.

MANNING, J. H. 1957. The Maryland soft-shell clam industry and its effects on tidewater resources. Maryland Dept. Research & Education. Resources Study Rept., No. 11, 25 pp.

MANNING, J. H., AND K. A. McINTOSH. 1960. Evaluation of a method of reducing the powering requirements of soft-shell clam . Chesapeake Science, 1(1): 12-20.

MEDCOF, J. C. 1961. Effect of escalator harvester on under-size soft-shell clams. 1959 Proc. Nat. Shellfisheries Assoc., 50: 151-161.

MEDCO", J. c., AND J. S. MACPHAIL. 1955. Survey of bar clam resources of the Maritime Pro­ vinces. Bull. Fish. Res. Bd. Canada, No. 102,6 pp.

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