,1•

t 0 t he au t il 0 I~

International Caunei1 for~ ~ Exploration of thc Sea

c., ,'72/K:3GShel 1fis hall d ße n t i1 0 S Co 11)111 i l: 1: e e

•

•

by

D. J. Scal-ratt'Fisheries Research Board cf Canada

Jepartlncnt cf tile [IlVil~Onf:1ent

St. 1\ nd i"t: ':/ S, iJe \'/ 8r LI n s ~'I i c kCanao,)

Introduction

Ti1 e se a\'1 c ed 1I (1 r ve s t f rom t /1 e CCl na ci 1an At 1d n t ich d 5

i creaseJ in value f)"om S:iJ,0i);) in thc 1940's to about 53 millionin lJ70. Thc ['lrinciral srecies is Ir'iS:l 1Il0SS (Cnondrus crispus)\'Iideh gro\'is froPl UJ.i to 6-81111n a liu!'1ber of t'OCk)fat'eas~-- ---;:\l)prox'i­ma tel y 11 a 1 f t hc ha r ve s t i s f t' 0 in Pr i ne c Ed \" i1 r cl I s 1a nd \'1 her e ,criginal1y, iilOSS dislodqed by \/dVe action \'·/as qatilered off thebe a C!l 0 l~ i 11 t he S II r f . ;. 1 te r na tel y a hil ncl I' ak e \'1 a s us e Li t 0 I CO!TI i.i l

li1 0 SS 0 f f t :l e r eck s • S i n c e t il e Cd r 1y 1 J GO' s. t iJ e han d I' a Ke ha sbee n m0 d i f i e cl a nd mc c! a n i Zf~ .' • R<.I kr.? s a I~ e n0 VI U P t 0 3 m \.Ji cl e ,\'1 e i ghin 9 u P t 0 J 00 k g, a nd d t' e t (HI e don s tee 1 ca b 1e s by D 0 \'/ e rboats at speeds to 2 knots (1 misec). In \'/estern P.t.I., thisr a keis n0 \'1 t he p r i n ci;) d 1 n {t r v l: S tin Cj !Ti f:: t 11 0 d • I n east e " n P. E • 1. ,the presence of tne more delicate commercially valuable weed,Furcellaria fastiqiatil, amonq the moss, has inhibited thedeve-loprne-nt öTdr-aq---rdKing dS Cl harvc:sting method.

A'1 1 d r e a s \'1 i1 c r e Ur 0 11 d r us r:; r 0 \'1 5 are als 0 fis hc d f 0 rlob s te r s • T,1 U s i t \./ a s i ne vlt""ä"FT-e- -t hat t h e s p re a d 0 f d Y' a q r a kin qfor Irish !TiOSS would bc opposeJ by conservation-minded lobsterfisherllien. The ques ion of damdge to lobsters by moss ra inCjfirst arose in eastern Prince County, P.C.I., \'/here raKersobserved that crushed lobsters or narts of lobsters were beinaf 0 und i n t herak e 5 and s pe c u 1d ted t It a t mo red amag e ~'I a s bei nq ­caused than was actually seen. Observations aGoard commercia1boats. and under \'1ater,suqqested thc total damage was i nconsequt-:n­ti 1 and rakilHJ was permitteJ to c0J1tinue.

The spread of rakinq inta the north shore of Queens C·.,P • E. 1., i n 19G9 \'/ a s v i 9 0 t' 0 U S I Y 0 Ppos e d bY 10 Call 0 bs te r fis 11 e r 111 (l n •~ore lobsters were seen in moss rakes here than in areas further\-1 e s t a nd fis r e r !TI e n be li e ve d t n a t s (~ rio u s da !TI a ge \-/ 0 u1d res lJ 1 t i fraking were al10wed to continue. An investigation was initiated1n i·lay 1970. It souqht to compare trle darnaqe observed aboardcOlllllercial 11l0SS rakers on different grounds, and using divinqechniques. to investiqate the nUlilbel~s of lobsters on 1lI0SS beds,

their reactions to rakin", and the "umbers ki11ed or damaqed.Tnis would enable the effects of moss raking to be explained andp red i C ted, a nd t IJ e pro ba l.> 1e c 0 S t s (i n d () 1 1ars) C 0 In par ed \.Ji t 11profits to fishermen.

This pafler summarizes l~esults of the 1970 and 1971investigations. A more d€tailed renort will ße published else-where.

ilethods

.::.O.::.b-=s-=e:...:..r-=v~a::-;t::-;i:...:o::..:n:..:..;s;;...;.~a~b_..:.o..:.a..:..r.-:d:..-_c_o_m_m_ec:....:.-r..:.c~i..:.a-,lm...:o:...:s:..:s ra ki n9. ve s se 1~ •

An observer accompanicd moss boats se1ected at randomfrom a number of ports in Prince and Queens Counties. A fu11count was kept of -all' tows made each day. Moss landings wcreestimated or the weight obtained from buyers l records. In 1970,a few tows were timed by stop-watch and crude estimates of towingspeed made by stop-watch timing chips of wood past measured ­distances a10ngthe boat's side. Lobsters, or parts of lobstersrecovered from the moss, were measured with a vernier caliper.

In 197,1, follo\-linq repeated 10bbying by lobstermenlsassociations, a temDorary ban was imposed on moss rakinq inQueenls County whicll restricted observations to Prince Countyboa t s • Si mil art'ec0 r ds \,/ e re ke pt, c xcept t hat ca ch 0 day te n to \'/Swere timed and ten cstimates of towinq speed were made usinq am(Hf i f i ed s hip I s log. I t \'1 as ass uI!led t 1\ a t boa t S pe ed wau 1d 9 i vei;reasonab1e cstimate of rake specd~ 'hence distance trave11edarr~ area raked could be calculated.

Lobster abundance estimates

Selection of samplino sites in 1970 was made fol10wings ur vey 0f t he mo s s be ds fr 0 nl a" man ne d, t 0 \'/ edun der~,a te r s 1ed(Fou1kes and Scarratt 1972). A section of moss bed, 300 m lang,\-/as selected and marked off as an experiment.a1 zone from which 'commercial rakers were cxcluded. '

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Initial ,lobster abundance cstimates wcre made by diver~c6unting and collecting all 'lobsters found within a 20.3 m2 arcaenc10sed\'iithin a square foldinq metal frame, \'Ihich \',as set fourt i r.1l~ s a t each s t d t ion (S ca r rat t 19fi a) , L a tc r, an i r.l pro ved met h 0 dwas developed using two 50 m lang lead-co~ed lincs laid individual1yat cach station. iJivcrs, carrying il metal rod, 1 m lonq, collectcda11 lobsters \'Iithin a r.lCtre of one sidc of each linc. Each station\'/ a s ' t hus 10 ~ m2 • 11 0 te s \'/ c rem il cl e 0 f de fl t h, bot tom type, i den ti t y •and abundance of seaweeds and ~iljor fauna.

~eaction of 'lobsters to movinq rukes

. Initially, two standard 3 ft (0.9 m) rake units wererigged together with a polypropylene rope brid1e. Later thisbridle was replaced by chain slings and a stecl pipe spreader barto which the rake units \lere shackled, ,thus duplicatinq cor.lf'lercialpractice. A 12mm diametcr Dolypronylcnc line, 5 m 10ng, knottcda tin t e r val s, \'/ as fa s t e ned tot hc end 0 f t hc t 0 \./ r 0 pe. f, d i verentered thc uater holding this rope \'1itl1 tllc boat movin9. ThcI' ak es \'/ e r e pus hed 0 ver boa r dan d t i1 c t (Hol r 0 r e pa i U 0 u t . 0nce' t herake 'started movinC/. the Jiver' not~d 'lolJsters seen in, or'c'scanil1!1fra m, t he pa t hof t hera ke • Co un t \oJ a 5 kept 0f t h0 sethat: a)a va i ded t he rake co rn p1e tel y; b} t 0 uehe cl 0 l~ \'/ e reh i t bY t hc rakebtit were uninjured; c) lost logs or cla~s or suffered minori nj ur i es; cl) ki 11ed 0 utri !J htor sos C " i 0 us1Y \'/0 und ed t il at s ur vi val\,/ 'a 5 un1i ke 1y • Each ' t 0 \,/ \/ i.1 S 3 in i nut e s 10 n!1 • f\ f t e r ca c !l t 0 \1, t hcdiver rep6rted lobstcrs seen to an assistant on deck. Usual1y 12to \-/ S \'/er e 0 bse r ved ins cq II ence,

Rake track examination

, Ta determine \'Jhether more lobsters were killed or injuredthan wcre seen by observcrs, sections of rake track approximatelylbo m2 inarea were examined. Lead-cored, braided nylon lines,50 m 10ng, He i giltedan tI buayed a tone end, \-/ C rc t hre ade d t hrau 9h9ui cl e s 'I' e1dedon each s i deo f t herake • nu 0 yS, \'/ ei CJ ht s, an d ra ke

• 6 ••

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Hcre pusiled off the stern of thc boat in sequence and tiw lines"pa i d 0ut toma r k e ach s i deo f t he t ra c k \'1 h ich \1 a s abo ut 2 m \'1 i de .Divers began to examine'the track immediately·the1ines" had clearedt he gui des . lob s te r S 0bse r ve d be hlce n t he ' 1i ne s \'1 ere co 11e c ted 'and examined.

Towinq speed ca1ibration

Surveyboat :towing speed was adjustedby experience' tomatch commercial practice. In 1970~ a number of tONS were timedpast ma,"ks set 50 m apart to give a r:lOre accurate "estimation ofra kin 9 s pe edan d i n 1971, a num be r 0 f tiMe d tO\'1 S \'l e remade VI1 t h ' a nodometer whee1 fastened to the rake and connected to an eventrecorder on deck. Raking speeds sO'estiMated ware compared withboat speedsrestimated "'/ith: the ship's log •

. Results and Analysis

Ob s e r vat ion s abo ar d mo s s ra kin q bo il t s_ (T ab 1es" 1 an d 2)

Rake sets are normally rigqed with two or three standard3 f t (O. 9 In) uni t san asp ,. cade r bar. ß0a t s \lJi t h t \110 .set s 0 fra k esnorma11y work,'them alternate1y so thatone is being set for rakingwhile the other is being haulcd back for the moss to be removed.On go 0d mo s s qrau nd s, t hera kes' f i 11 : ,.ap i d1y ü nd to H dur a t ion i sdetermined by the time taken tO" clean rakes. On paar or marginalgrounds. tow duration incrcases. Same boats fit Nire mesh baskets.to the rakcs,to cat~h dislodged moss. '

Twenty-one days' observations were" made in 1970 'and 19"day s lob se r va t ion s i n 1971• i tean bo J t s pe e d \,/ a s abo ut 35- 90 cm/ sec.~ean tow duration' in 1970 was 2 minutes 10 seconds, and in 1971,3 minutes 40 seconds. ßoats made on avcr"age alJout 150tows ,per"day. Most 10bsters'were secn'p~rday in Queens County and fewestin W. Prin~e County. The ~ean cstimated sizc of.44 lobsters foundin rakes in 1970 was 44.4±8.8 rnm carapace length. All were be10wthe miriimum legal size limit of 63.5 mm c.1 •

lobster abundance (Taule 3)

lobster abundance,vas lowest on the smooth, flat bedrock1edges off :\01. Prince County, iligher on the medium rough moss bedsoff E. Prince County,and highest on the 'heavi1y boulue," stre\'ln:Queens County bcds. The Queens County beds also showed increasein 10uster abundance on rnoss bedsfron spring to summer. At ~he

time 0 f ye ar \'1 he n rlO s s r akin ~J \1a s, 0r \10 U1d hil ve l> e e n, il t . i t s ?

peak, lobster abundance on Queens County beds averaged 9.4/100 m~.

Tllere' \'/ere no differences in lobsterabundance betucen stationssampled in 1970 inside the zone'closcd to commercia1 raking andthose sampled outside (Scarratt ns 1971). :Iean size of lobstcrson moss beds \las bet\'leen 3J'and 42 mrn c.1.

oamag e 0 bs e r ve d f r 0 r~l no vi..!!.9 r a kCl ~_ ( Til b1e 4), '", . ,"

One hundred and cighty-ninc 3-min tous uere observed bydivers'riding the rope-brid1ed rake. Darlage observed \las less thant hat see n i n 165 d i ver .. 0bs e r ve d tO\'1 S . \.Ji t h . t 11 e c hai n- br i d 1e d r a ke ,suggesting thatthe 'heaviel", noisier chain-bridled rake \'lithitsheavy spreader bar is mor~ lethal to lobstcrs. ·tl series of tO\'lS' ,\'11 t h altern a tin q s 10\'1 a nd f i1 S t hau 1- bil C k s hO\'1 e d t hil t h i 9her r a kespeeds caused slgnificantly m'ore observa1Jle damage. Tlle majorityof lobsters seen avoidcd the rake or escapcd injury but SuusCCluentcalcu1ation showed that only a fraction (19-72%) of those esti~atcd

to 1>e in the path of' tile rake, had Ileen seen to r'espond (Table 5).Tlle fate' of lobstcrs not seen could '~ot bc determined by-this methodej·lany bouluers \'/cre rolled or displaced by the rakesand" a highproportion of the noss cut l'Ii1S not col1ected.

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Exa~ination of rake tracks

•Accordinq to Ffrench (1971), 25.hoats \'Iorked the QueensCounty beds in 1970 for an averaqe season of 65 working"days each.From data in-Table.l, each boat wOlJld rake between 3~8 to 5.7hectares (double or triple rakes) at 130 sec mean tow durationor 6.4 tO.9.6 ha per .day at 220 sec tO\oJ duration.

Twcntv-five frcsh, 50 n 10no, rake tracks were examinedin August and S~ptember 197Q (Table 6). Twc1vewere on comnerciallyra ke d 9rau ndsan d 13 \'J e re 0 n t he c los ed Z 0ne . f\ tot a 1 0 f 13 f res h1Yki1led lobstcrs was found out of 225 examined. Hany had beencrushed bet\'Jecn boulders ratller than hit bythe rake. There wereno differences between the areas open and c10sed to commercialraking •.Lobster ahundance on· Queens' County moss beds at this timeof year.is about 10/103 m2 , .thercforc 13 lobsters killed rcoresent5.2~ of the exposcd population. .

I 11 1:) 71 in. E• . Pr i nce C0 un t y i n 17 t r ac ks, t\'I 0 de Ci dlob s te r s \'1 e rc f 0 lJ nd \11 h ich reD r p. 5 e n t aha lJ t 25: 0 f t he 99 c s tima ted t 0be in tlle rake patil. In 59 tt~acks examined in Queens County inJuly 1971 t after the ban Oll rllkinCj had been inposed, only sevende a d lob s t e t' s \'1 e re f 0 u 11 d 0U t. 0 f 3[) ~ e xami ncd. Fra m lob s te rabu ndan ce e s tima te 5, t he nu PI be rexpe c ted inS 0 t ra c ks i 5 42 5 • Theseven dead lobsters represent 1.6~~ of thc theoretical population •i n t her a ke pa t h • This iss i 9n i f i ca n t 1y 10\'Je r t ha n t he 5. 2 /~

observed in 1970 \'/henC0Il1I11Crcidl rakinq \-/as in proq)~ess~

.To explore the effect of intensive rakinq o'n QueensCounty beds, a nUl1lber of tracks \'/ere exami ned in a - smd 11 area,. thcare a \'1ast he n ra ked f 0 r 2- 3 iJ () urs a nd t he n mo re t ra c ks \,/ e reex ami ne d (T ab 1e 6). Tlt e ~ umher s a t' C S I!l all bu t O~) se r ve d I~ 0 r tal i t y( 2/ 59) a f t er. i n t e ns i ver a kin q \'1 a s h i C) her t ha n be f () r c ( 0/ 119) (Z :,2.4, p = 0.016). This sugqests that rakin9.mortality in undisturbedpopulations is lower than in heavily rakcd populations dnd confirmsthc hiqher I'lortality estimatc for .Queens County in 1970.

The mean carapace length of lobsters found kil1ed inrake tracks was 35 mm. The high incidence of cla\ll lass (up to 25%)an d \'10 und i ngin t he ses n1 all lob s te r s i s pos s i b1y . d ueta ra kin 9 bu t~lso partly to:winter iee conditions.

Estimate of damage attr:Lb_u_t.2.!>J.~..2-ra~in9 in Queens County, P.E_.I.

\ ....The"number':6'f Totrsters in 5.7 ha is about 5,360 of \'!hich

5.2% or 280 might bekilled. .

.From unpublished infor·mation on mortality rate of small'lobsters (Scarratt in preparation) and the value of commercial1yca u9ht lob s te r s, t he pot e nti al val ue 0 f 35 mm c. 1. lob s te r s i sestimated at 8t each. Thus damage by each raker per day can beestimated at $22.36 with a fleet season total of $36,000.

An a 1ys iso f buye r sire c0r cl s s h0 \'1 74;~ 0 f mo 5 5 ha r ve s tedi n 1970 \'1 a s 1a nde d by, r a ke r 5 • The s e aso ns I tot a 1 was \'10 r t h $263 , 250of \IIhich $198,000 can be attributcd to rakinq. Lobster landings in1970 \'/ere $514,000 (official statistics). Thus adamage estimateof $36,000 is cquivalent to 18% of the moss rakcd or 7~ of thelobsters landed. .

tonclusions

Damage to lobsters by moss raking is re1ated to theroughness·of thc beds and lobster abundance on them. On smoothbeds t lobster populations. are low and mortality ncgligible. Onrough grounds, lobster populations are high and damage to themjustifies SOI:1C control,of r'al:inq activities.

, $,'1,,,,

.< , ...,.,...... ',+' ~-_I'.'...."',~~-.\'-'OJ;,#i;.. ""-"'-4""i ~.,(. .' -..ut'-" " ""',,, ..... ".'~...; .....~,.,...... '".R>fi .........-...·· ....t... ,_

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l3 i b1 i 0 q rap :1 y

Ffrench, n. A. 1971. A current appraisa1 of the lrish mossindustry. Dcpt. Fisheries und Forcstry, Ottawa. Canada,Feb. EI71 t 230 p.

Fou1kcs, T. J. t and D. J. Scarratt. 1972. Design and performanceof TURP - a diver contro11cd towed underwater research plane.Fis h. Res. Bd. Ca na da, Tee h. i: e p t. ~I o. 295, 15 p.

Scarratt, D. J. 19G3. An artificia1 reef for lobsters (Homarus~1e r i ~2.!I.J!..~) . J. Fis h. Res. ßd. Ca nCl da 25 ( 12 ): 2(j g 3- 2G90:---

1971. lnvcstiqation intQ the effects of Irish 01055

rakinq on lobsters. Fish. F~es. Gd. Canada, ;\S Rept. Series,iI o. 11:) S t S t. fi nd re \J S, r:. 13 ., ,) all. 197 1, 35 p.

. '{'..... ,.- .....,

• $ •. '

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Table 1. Summarizcd obscrvctions JboJrd moss raking hoats in197,') and 197 1 • T0 \/ S tl eedan d dur a ti 0 II iH e LJ a:; edon18 obscrv3tions per dayls raking.

: ;.~ J n ;1c: ,) n t 01'1 Tot i1 1 n 0 •

Di1 .y s t 0 \./ S tim Ce! Sp e cd i1ea n \I t . 1{} bs t crsy~ar Cil U n ty _~..Q..!: v c:~__p_~~:.._d..~,'L....._._?-_~~__~~_~e.c 010 S s 1a n cl e d see n

197]

1971

:L Pr;ncc .) 13G 7:1(1 745 kal..) .1

E. Prince 2 lG7 123a 85 3 1410 11

Queens 11 1GG 130u 3°c lGaO "'0

LI • Prince 12 123 218 85 795 11

E. Pl"incc .., 1GLi 22·1 91 305 IlI

2

..,,.dL:J

7-------_.._---_.- ._-_._..._-_..__.-._-------------

a 1 boatb- G boatsc 3 boatsd plus 14 lobsters taken unnarmed in baskets fitted to rakes in 2 day's

rakil1~.

Table 2. Hean number of lobstcrs seen per day in commercial mossrakes.

-J< Excludes thosc takcn uninjul'cd in baskets

County

E. Prince

Queens

1071

0.25

1.0

~.5*

1971

0.33

1 .0

no raking •Tab1e 3. Lobster abundance estirHtes and mean carapace length at

sample stations i n 1971 and '1971 • tleancarapace

Stf.ltions Lobster's? 1engthCounty Dates \'/0 rk ed :10/100 m'- mm

..._-- 1970----··--··--'1 :>dQueens :·lay / Ju ne G t • c... 37 .7

June 14 10 . :J 3'1.4

Ju1y 1 :> 9.4 39.2

1971lL Prince Junc 29 n.7 39.5

E• Prince July 9 5.8 42.4

Queens Ju'ne . 1 (~ 6.3 39.0

Ju1y 3 8.5 40.0

l\uC)ust (3 10.3 3(1.6

a

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Tab1e 4. lobsters obscrved by divers during3-minute rckc""towsin 1970 and 1971.

Number of lobstersT0 Ws Av0 i d Hit, Li 9h t -K i 11e d ,

_y...;..e_a_r S_e_r_i_e_s n_u_l_nb_e_r_r_~ke_~qamaqed \o,Jound crushed Tota 1

a) Rope-bridled rake:

1970 Queens County

b) Chain-bridled rake:

189 4· 72 24 13 1 ,005

1970 Queens County

s 10 \'1 tO\'/S 24 102 82 6 2 192

fas t tO\'/S 24 79 73 6 3 171

Queens County 43 1.1·1 120 23 4 231

1971 [ . Prince County* 9 35 27 7 2 71I

1971 Queens County GO 177 398 37 7 619

Sub-total 165 -177 705 79 23 1284*------------_._,.-_._---- ._._--_._-_.

made by a cornr.1Cl'cia1 boat: mcan ,-ö ke speed 73 cm/sec; mean tO'"duration 1 30 sec.

')

Tab 1e ~. Lob s t e l~ r 0 pul a t i 0 11 cl e ns i t y, no! 1:} 0 Jl1 L. e s t i r.l a t e 0 flobsters in tile path of rc"d:e, mean nurnbcl4 s observecldur i n q 3 - n i n LI t e t 0 \'1, d n d nw a 11 n umb e r S re c 0 ver e cl f rom100 n 2 rake tracks.

?

Ho/II10 OlL. Estinatcd ilcan number llean numberlobster number obscrved in rake ~rack

Da te_~~~_n_t.! ~p~'I~_t i ~_n ~!.l_Y_c:_~.~~. ~0. r_.~:l~~ (1 ~.E..-:l~l_,_.__.__1970

July Queens ()'lJ •• , 5.5

J\uqust 11 ~).3 rOflC bridle

7.5 chain bridle

9.0

September "

1971

4.3 9.0

J ul y

J ul y

E. Prince

Queens

11

8.5

10.3

11 • ab

') (1 • c'- :.> • Lj.

7 • ;)

G.G

12.9

6.2

6.6

8.0

.1.8 d

September "

a Towing speed = 3D crn/secb Tow duration = 2 min 10 sec tows at 73 ern/secc Towing speed = 79 cn/sccd Rake tracks examineu ofter previous intensive rakinq.

5.6lO.Od

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Tab1c 6. Lobsters obscrved in frcsh 50 m long rake tracks

102

123

(j4

5

3

3

21

32

GU

74

2

il umber iJ umber s 0 f-.!:.Ql? s_t_e_t_'s~ _of Not ~issing 01d New

Yeare 0 UI~ t r acksexaI~ i neu Uncl cl mag c cl c 1a\'I S ~I 0und s wo und s Dea cl Tot a1*-_. .._.--- -_._--_._--------_.- ----------1970 Queens

1971 E. Prince 17 (1l) 80 12 6 1 106

Queens 5D 17 213 G1 27 23 7 350

(Ju1y)

Queens

Queens o ...77 20

nU

11

3

7

4 2 53

* Totcl1 is of number of lobstc:t's.in tracks. It r.lay inc1ude lobsterswi th more ·than one type 0 f \'lOlJ nd .

a within area closed to fishermenb on commercially rakcd bedsc 0 ne lob s tc r pcl r t 1y C0 11 S Ut:w d bY a rIphi po LI s"d tous made before intensive rd~ing

e t 0 \'1 S 1:1 aJ e a f t e r i nte ns i vera kin ~l

64° 63° 62°-y----------rl----------TI---------- -

~ Irish Moss Growing? Areas Examined ".•..

~

Prince EdwardIsland

NewBrunswick

/Nova Scotio

Flgure r. Prfnce Edward Island, showfng Irfsh mossbeds examfned.