This serles includes unpubl1shed preliminary reportsand data recorda not intended for qeneral distribution.They Mould not be referred to in publicatl.ona with­out clearance from the lasuinQ' Board establishment andwithout clear Indication of their manuscript status.

FISHEBIES BESEAB£H BOABDOF £ANADA

MANUSCRIPT REPORT SERIES

No. 1119

Juvenile Sablefish Cruises in 1970, Including

Length, Weight, Girth and Age Data

byW. A. Kennedy

Bioi.... Statio.., N.........., B.C.

November 1970

This series Includes unpubl1shed preliminary reportsand data records not intended for Qenera! distribution.They should not be referred to in publications with­out clecm:mce from the IssWnQ Board establishment andwithout clear Indication of their manu.scr1pt status.

FISHERIES RESEARCH BOARDOF CANADA

MANUSCRIPT REPORT SERIES

No. 1119

Juvenile Sablefish Cruises in 1970, Including

Length, Weight, Girth and Age Data

byW. A. Kennedy

Biological Station, Nanaimo, B.C.

November 1970

PURPOSE

1. To get living juvenile sablefish for "fish farming" experiments at Nanaimo.

2. To test gear and equipm,ent designed to improve methods of capturingjuvenile sable fish and of transporting them.

3. To increase biological knowledge of wild sablefish, particularly suchaspects as are likely to be applicable to convnercial sablefish cuI ture.

FISHI N3 METID!:6

Most of the fish taken were caught by baited hooks, either on floatinglonglines as described in Manuscript Report No. 1059, or on handlines.Herring was used for bait as in 1969, but chunks of sablefish were also used,and proved excellent bait for sable fish. A chunk of sablefish stays on thehook better than does a chunk of herring.

Other gear was tried as possible alternative ways of catching sablefish.A fyke net was fished both on the bottom and at the surface of the water.Crab traps were fished both unmodi fied and IOOdi fied by changing the triggersor by covering the trap wi th finer mesh. Several hauls were made wi th a beachseine.

TRANSPORTATION OF FISH

In 1970 all fish were moved in tanks set up on deck. Sea water waspumped into the tanks continually through hoses ordinarily used for washingthe deck. During the first two cruises a pair of open canvas-walled tankswere used, the canvas being supported by a metal framework. On the last cruisea pair of rigid 500-gallon oval fibreglass tanks were used. They were fittedwith removable plywood covers which could be bolted in place. With deck hosessupplying sea water at full force, they were kept filled to the lids, thuseliminating surge while travelling. Also, during the last cruise, air (fromthe ship's compressed air supply) was forced through airstones in the tanks toaerate the water.

CRUISES

First Cruise

M/V A.P. KNIGHT went to Bull Harbour and Port Hardy during May 11-21­Only one sablefish was taken during 60 hours at Bull Harbour during whichfloating 10ng11nes, handlines, and fyke net were fished. But at Port Hardyit was very easy to catch small sablefish by handline -- for instance, theship's crew caught 75 of them in about 20 minutes by handline on May 19.

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The fyke net was fished four different ways during the cruisel

(1) without leader, on bottom, with bai t in the final poti(2) without leader, on bottom, unbai ted;(3) with leader, on bottom, unbai ted;(4) with leader, floated so that top lines were just below the water

surface, unbai ted.

A total of 163 hours fishing wi th the fyke net took only 2 sable fish.

About 275 liVing sable fish were taken, almost all by handline. Mostof them survived transportation from Port Hardy to Nanaimo and they werelively when delivered. Because of '{)pen House" they were not counted untilJune 3 when there were 257 of them. By August 24 there were 146 fish, 111 (43%)having died since June 3 (33% during the first 4 weeks, 8% during the next 4,and Z' during the last 4).

Second Cruise

A variety of gear was fished during a cruise by M/V A.P. KNIGHT to PortHardy, July 7-16. A fyke net was set wi thout leaders where it would besubmerged at high tide but mostly out of water at low tide; it was oriented sothat any sable fish which came into the area during high tide would tend to beguided into the pot as the tide ebbed. No sablefish were caught. A beachseine was hauled several times without taking any sablefish. Probably theshallow water in which it was necessarily operated was too warm for sablefishat the time; possibly a beach seine would be more successful at the same placein Mayor June. Modified crab traps caught a few sablefish, indicating thatfurther modifications should be tried.

Most of the sablefish caught during the cruise were taken by floatinglongline or by handline. The vessel left Port Hardy with 406 liVing sablefish.Only 189 were alive when they reached Nanaimo, and there were only 28 survivorsby August 14. The high mortality rate during transportation is attributed tohigh water temperatures and the heavy mortality (85%) sUbsequently isattributed to unknown after -effects of high water temperatures during trans­portation.

Some surface seawater temperatures recorded during the cruise were:

(59 F)(55-59 F)

(54 F)(52 F)(54 F)

(59-68 F)

15 e13-15 e12 eHe

Cape MUdge 12 C15-20 e

at the small boat harbour, Port Hardyslightly to seaward of aboveoff Malcolm Islandat Alert Bayat Blinkhorn, Seymour Narrows,Strai t of Georgia

Sable fish were not captured in water that was warmer than 13 C (55 F).

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Third Cruise

M/V G.B. REED went to Minstrel Island, Port Hardy and Fort Rupert (nearPort Hardy) during August 23-31. Only floating longlines and handlines werefished, 90% of the catch being taken on handlines.

Fishing for sable fish at Minstrel Island, at specific localities wherethey had bee" caught in 1969 with the same gear, was unsuccessful. Sablefishwere easily caught near the surface at Port Hardy near the cannery. But mostof the fish taken were caught by handline off Fort Rupert in about 17 fms ofwater.

Taking advantage of lessons learned during the previous cruise, fishwere carried in 500-gallon fibreglass tanks with lids, the water being aeratedby airs tones. Furthermore, the detrimental effects of using undesirable warmStrait of Georgia water in the tanks was minimized by scheduling the vessel todock at 9 AM after a nighttime passage of minimum duration through the Strait.

Presumably because of these precautions mortaH ty both during trans­portation and later was lower than usual. Mortality was less than 5% duringtransportation and 425 sable fish were delivered alive in excellent condi tion.Mortality during the next eight weeks was 28%.

LE!'li1H, WEIGHT, GIR1H, AND AGE DATA

A sample of 114 sablefish was taken from the fish caught at Port Hardyduring the second cruise. They were taken at random at the time of capture.Fork lengths to the nearest millimeter and weights to the nearest gram wererecorded shortly after death. Girth was also recorded for a subsample of 16,girth being determined by finding the length of string needed to encircle thefish at the place where girth is greatest. Several scales were taken from eachfish for subsequent age determination.

A representative sample of 21 sablefish was taken from the fish landedalive at Nanaimo at the end of the third cruise. Since some fish had diedand been discarded between the time of capture and the time of sampling, thesample was not necessarily representative of the sablefish at Fort Rupertwhere most of the catch had been taken. Fork lengths in millimeters andweights in grams were recorded shortly after death. Several scales were takenfrom each fish for subsequent age determination.

Length-Weight

When the weights of the individual fish in ei ther sample were plottedagainst the corresponding lengths on log-log graph paper, the points tendedto be along a straight line. The equation for the best straight line througheach set of points was derived mathematically by standard methods. Theequations arel

for Port Hardy data y = 3.13X - 5.35

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for Fort Rupert datafor the two combined

y = 3.49X - 6.30Y = 3.08X - 5.22

where Y is the logarithm to base 10 of the weight in grams, and X is thelogarithm to base 10 of ~he fork length in millimeters.

The Port Hardy and Fort Rupert lines do not di Her significant! y inslope but their "intercepts" ~ significa[ltly different (p = 0.05). Over thesize range corrunon to both samples Port Hardy fish of a given length weighedabout 14% more than Fort Rupert fish of the same length. Perhaps Port Hardyfish had been better fed (by offal from the cannery?). Alternatively thedifference might have resulted from selective mortality between time ofcapture and time of sampling. Because of this doubt, I consider the linebased on the Port Hardy data alone as more meaningful than the line based onthe combined data.

The above equations can be put in parabolic form by taking antilogs.The resul ting parabolas are the curves that would fit the length-weight dataif plotted arithmetically. The equation of the parabola that fits the PortHardy data is:

y = 0.00000450x"<13

where y is the weight in grams, and x is the fork length in millimeters.

From the logarithmic form of the Port Hardy equation It is alsopossible to derive:

w= 3.131 - 5.21

where Wis the logari thm to base 10 of the weight In kilograms, and L is thelogari thm to base 10 of the fork length in lIlillime'&eP6. C...AlT ....... r!C:u.

A length-weight relationship based on a larger sample of sable fish witha much greater range in size was reported in Technical Report No. 74. Theequation (where Wand L were as above) wast

w = 3.14L - 5.24

There is no significant difference (p = 0.05) between the two equationsin ei ther slope or intercept. In other words, the length-weight relationshipof Hardy Bay juvenile sablefish is consistent with the length-weight relation­ships of other sablefish as reported in Technical Report No. 74 (i.e. I allsizes of fish, from the Gulf of Alaska, Perouse Bank and offshore from Oregon).

Because it is often easier to measure length than weight, partiCUlarlywith living fish, Table 1 was derived from the Port Hardy equation. Itenables collectors of juvenile sablefish from Hardy Bay to find approximateweights easily. Presumably the indicated weights should be decreased by about14% for Fort Rupert fish.

L-______________"_

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When girths were plotted against lengths on log-log graph paper thepoints tended to lie along a straight line and the same was true when girthswere plotted against weights. The respective equations of the straight linesfi tted to the points mathematically were:

G = 1.08X - 0.509and G = 0.359Y + 1.28

where G is the logarithm to base 10 of the girth in millimeters, X is thelogarithm to base 10 of the fork length in millimeters, and Y is the logarithmto base 10 of the weight in grams.

By considering the maxillJJm fish girth that would be expected to gothrough a mesh of a given size the values for Table 2 were derived from theabove equations. The values for Table 3 were derived by considering themaximum fish girth that would be expected to go through a pipe of a givendiameter. Tables 2 and 3 are useful for planning sablefish rearing facilities.

The scales were prepared and mounted as described in Manuscript ReportNo. 1086. Standard scale reading methods were used to determine ages; generalcriteria were used since specific criteria for identifying annuli on sablefishscales have never been formally validated.

An age determination was made for each fish on each of two occasionsseveral days apart. In all but three cases the two independently madedeterminations agreed (98% agreement). Cases of disagreement were reconciledduring a third reading.

On the basis of scale readings, 90% of the Port Hardy sample and all ofthe Fort Rupert sample were age 1+, Le., were fish that had passed one mid­winter birthday and were now in their second year. The rest of the Port Hardysample were age 2+. None of the fish sampled were less than age 1+ or morethan age 2+.

Tables 4 and 5 show respectively the relationship between length andage and between weight and age. As would be expected, most age 2+ fish arelonger and heavier than most age 1+ fish but a few of the biggest 1+ fish arebigger than a few of the smallest age 2+ fish. Had the Port Hardy fish beenclassi fied !. priori as 1+ if shorter than 400 rrrn (15.7 inches) and 2+ iflonger than 400 rrrn, only 2.6% would have been incorrectly classified. Alsohad they been classified as 1+ if lighter than 700 g (1.6 lb) or 2+ if heavierthan 700 g, only 4.4% would have been incorrectly classified.

On the average, 1+ fish taken in August at Fort Rupert were 30 nun(1. 2 inches) longer and 60 g (2 oz) heavier than 1+ fish taken in July atPort Hardy.

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AGKi'llWLElXiMENTS

The 1970 cruises were successful largely because of the cooperation,skill and diligence of the captains and crews of the vessels A.P. KNIGIT andG.B. REED. M. S. Smith organized and executed almost all of the preparationsfor all three cruises. W. P. McGee ably assisted wi th sampling.

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Table 1. Expected weights of sable fish at given lengths as estimated fromthe relationship between length and weight based on data from a sampletaken at Port Hardy in July 1970.

Length Wei9ht Length Weightin in in in

inches pounds millimeters grams

10 0.33 250 147

10 1/2 0.39 .260 164

11 0.46 270 184

11 1/2 0.53 280 206

12 0.60 290 230

12 1/2 0.68 300 256

13 0.76 310 284

13 1/2 0.86 320 314

14 0.96 330 346

14 1/2 1.07 340 380

15 1.19 350 416

151/2 1.32 360 454

16 1.47 370 496

16 1/2 1.62 380 540

17 1. 78 390 587

17 1/2 1.96 400 636

18 2.15 410 688

18 1/2 2.35 420 743

430 801

440 862

450 927

460 996

470 1070

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Table 2. The maximum size of sablefish likely to escape through the webof nets of a given mesh size (stretched measure) as estimated fromrelationships between length and girth and between weight and girthbased on data from a sample of 16 sablefish taken at Port Hardy inJuly 1970.

Mesh Fish size Mesh Fish size

size Length Wei9ht size Length Weightin in in in in in

inches inches pounds millimeters millimeters grams___0

2 8.5 0.22 51 217 102

2 1/4 9.5 0.31 57 241 142

2 1/2 10.5 0.42 64 267 189

2 3/4 11.5 0.55 70 291 250

3 12.4 0.69 76 315 315

3 1/4 13.3 0.87 83 339 395

3 1/2 14.3 1.08 89 363 488

3 3/4 15.2 1.32 95 387 595

4 16.2 1.54 102 411 700

4 1/4 17.1 1.86 108 435 840

4 1/2 18.1 2.16 114 459 980

4 3/4 19.0 2.49 121 483 1130

5 20.0 2.82 127 507 1280

L..- ..

- 9 -

Table 3. The maximum size of sablefish likely to escape through pipes ofgiven inside diameters as estimated from relationships between lengthand girth and between weight and girth based on data from a sample of16 sablefish taken at Port Hardy in July 1970.

Pipe size F· sh size Pipe size Fish size

inside Length Weight inside Length Weight

diameter in in diameter in in

in inches inches pounds in millimeters millimeters grams

1 1/4 8.3 0.22 32 211 100

1 1/2 9.9 0.36 38 252 164

1 3/4 11.4 0.55 44 291 250

2 13.0 0.80 51 330 362

2 1/4 14.5 1.11 57 369 502

2 1/2 16.0 1.48 64 407 672

2 3/4 17.4 1.94 70 444 878

3 18.9 2.45 76 481 1110

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Table 4. The relationship between length and age in a sample of 114 sablefishfrom Port Hardy and in a sample of 21 sablefish from Fort Rupert. Notethat "270 _" means the number of fish with fork lengths recorded as 270 ­279 inclusive, "280 _" means 280 - 289 millirr.eters etc.

Length Port Hardy JUly 1970range Age 1+ Age 2+

270 - 0

280 - 6 0

290 - 3 0

300 8 0

310 10 0

320 14 0

330 9 0

340 9 0

350 15 0

360 11 0

370 0

380 2 0

390 2 0

400 - 1 3

410 - 2 1

420 - 0 0

430 0 1

440 0 1

450 0 3

460 - 0 1

470 - 0 0

480- 0 0

490 - 0 0

500 - 0

Fort Rupert August 1970Age 1+

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Table 5. The relationship between weight and age in a sample of 114 sablefishfrom Port Hardy and in a sample of 21 sablefish from Fort Rupert. Notethat "150 -" means the nwnber of fish whose weights were recorded as 150 ­199 grams inclusive, "200 _t1 means 200 - 249 grams etc.

Weight Port Hardy July 1970range . Age 1+ Age 2+

150 - 3

200 - 11

250 13 0

300 14 0

350 21 0

400 - 12 0

450 - 12 0

500 - 10 0

550 - 2 0

600 - 1 1

650 - 2 2

700 - 2 0

750 - 0 2

800 - 0 1

850 - 0 1

900 - 0 2

950 - 0 1

1000 - 0 0

1050 0 0

1100 0 0

1150 - 0 0

1200 - 0 0

1250 - 0 0

1300 - 0 0

1350 - 0 0

1400 0 0

1450 - 0 1

Fort Rupert August 1970Age 1+

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