and Atlantic Cod

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Distribution and Abundance of Haddock Melanogrammus antic C d Gadus morhua Eggs and Larvae aeglefinus in the Waters off Southwest Nova Scotia" Peter C. F. Hurley and Steven E. Carnpana Marine Fish Division, Department of Fisheries and Oceans, Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, N.S. 52Y $A2 Canada

Hurley, P. C. F., and S. E. Carnpana. 1989. Distribution and abundance of haddock (Melanograrnmus aeglefinus) ;and Atlantic cod (Cadus rnorhua) eggs and larvae in the waters off southwest Nova Scotia. Can. ). Fish. Aquat. Sci. 46(Suppl. 1): 183-1 4 2 . Synoptic ichthyoplankton surveys conducted at monthly intervals during the winter-spring of 1983-85 were used to determine the location, timing, and magnitude of spawning by haddock (Melanogrammus aeglefinus) and Atlantic cod (Cadus morhua) off southwest Nova Scotia. There was a marked similarity in the spawning locations of the two species: primary spawning occurred on Browns Bank, although lower levels of spawningwere observed on adjacent banks and in the inshore region. Cod egg abundance peaked in April in all years, while that of haddock varied between April-June.

A

I'hiver et au printemps de 1983 1985, des releves synoptiques de I'icktyoplancton snt et6 faits A intewalles rnensuels afin de determiner I'ernplacement, le moment et I'importance de la fraie de I'aiglefin (Meb~nogramrnus aeglefinus) et de la morue franche (Cadus morhua) au large de la rive sud-ouest de la Nouvelle-Ecosse. On a observe une similarit6 marquee des emplacements choisis par les deux especes : la fraie primaire a eke lieu sur le banc Browns, bien qu'knne fraie rnoins importante ait 6t6 observee sur les bancs adjacents et vers la c8te. Les oeufs de morue ktaient les plus absndants au mois d'avril de chaque annee alors que dans le cas de l'aiglefin, I'abondance maximale variait entre avril et juin.

Received April 19, 3 989 Accepted October 1 7, 7 989 (JA1.36)

kile many workers have reported spawning activity of haddock (Mebansgrammus aegiefinus) and Atlantic cod (Gwdus rnorhua) off Southwest Nova Scotia, none of the studies have been conducted in sufficient spatial or temporal detail to clearly delineate the spawning season or location. Previous work has shown that spawning of both species may occur anywhere between January and June, with peak spawning in April and May for cod and haddock, respectively (Bigelow and Schroeder 1953; Homans and Vladykov 1954; Serebryikov 1971; Grosslein and Hennemuth 1973; Scott 1983; Gagne and 09Boyle 1984; O'Boyle et al. 1984; Markle and Frost 1985; Koslow et al. 1985; Smith and Morse 1985; Sherman et aE. 398'7). The centre sf spawning has generally been acknowledged to be Browns Bank, with lesser centres on adjacent banks. An objective of the present study was to determine the timing and location of spawning of haddock and Atlantic cod off Southwest Nova Scotia, by examining the distribution and abundance of their eggs and l m a e . A second objective was to assess the intraseasonal, interannual, and spatial variability in location, timing, and magnitude sf spawning of these species.

Materials and Methods A grid of 95 stations off Southwest Nova Scotia was sampled once a month from February to June during 1984 to 1985. Sta'Fisheries Ecology Program Cesmatribution Number ; 14. Can. 9. fish. Aq~mt.Sci., VoI. 46, 1988

tions were spaced approximately 28 km apart, with additional stations in the vicinity of Browns Bank (Fig. 1). Two extra tramsects across Browns Bank were added to the grid in 1984 and 1985. Cruise dates and number sf stations sampled are shown in Table 1 . At each station, an oblique tow was made with a paired 6Bcm diameter bongo sampler, to a depth of 5 m off bottom or to a maximum depth of 200 rn. Sampler depth was determined from a Guildline conductivity-temperature4epth (CTB) sensor attached just above the sampler. The bongs frame was fitted with 333-prn mesh Nitex nets and volume filtered was determined fmm calibrated General Bceanics flowmeters centred in the mouth of each net. Vessel speed was maintained at 2.5 knots (I .3 d s ) and wise rates in and out were 50 and 20 daanira, respectively. During 1984 and 1985, tows at each station were replicated immediately, using the same starting location and vessel heading. Samples were fixed in 5% buffered fsmalin in seawater. Marble chips were used as a buffer during 1983. In 1984 and 1985, sodium carbonate was used as a buffer and samples were transferred to 95% ethanol after 48 h. Fish eggs and l m a e were removed and identified from the preserved samples in the laboratory. Samples containing more than 200 eggs were subsampled using the beaker split method (Van Guelpen et al. 1982) to obtain a subsample containing between BOO and 208 eggs. Eggs were classified into the following four developmental stages (after Makle and Frost 1985): Stage I, from spawning until the visible formation of an embryonic axis about the midgastrula; Stage II, from the end of Stage


could only be identified after late Stage 111, when diagnostic pigmentation had formed. Standard length of larvae (less than 18 mm) was measured to the nearest rnillimetre. Sample abundance was calculated as the number per square metre using maximum tow depth; station abundance was calculated as the mean of all samples available for each station.

Results

FIG. I . Map of study area showing station locations and geographic features referred to in the text: (A) Georges Bmk; (B) Fundian Chaannel; (C) Browns Bank; (D) Baccao Bank; (E) La Have Bank; (F) Roseway Bank; and (G) Bay of Pundy. Stations added in 1984 and 1985 ape indicated by circles (@). Contours are 180- and 200-111 isobaths . TABLE1. Summary of cruise dates m d number of stations sampled during this study. Cruise

Start date

End date

iV

Stage I CHW eggs off Southwest Nova Scotia were taken in all cruises, primarily on Browns Bank, but lower levels were encountered throughout the area, including the inshore (Fig. 2). Since Stage I eggs are less than 7' d old (Maak and Colton 1961; Fridgeirsson 1978; Page and Frank 1989), their distribution should provide a more accurate indication of spawning location than that of Stage IV. This assumes that the relative contribution of witch eggs is low, an assumption that is supported by studies showing that Stage IV witch eggs were largely absent from the Scotian Shelf prior to May (Markle and Frost 1985; Neilson et al. 1988). We found no Stage %Vwitch eggs prior to June in each of the 3 yr, with the exception of one station each in May 1984 and 1985. The temporal distribution of Stage IV haddock eggs was more variable than that of cod (Figs. 3 and 4). During 1983, haddock eggs were not observed off Southwest Nova Scotia until April, in contrast to their first appearance in March 1984 and February 1985. Cod eggs were present in February in all 3 yr. Peak haddock egg abundance was observed in April, May, and June sf 1983, 1985, and 1984, respectively, but substantial numbers were evident in June of all 3 yr. Peak cod egg abundance was observed in April of all 3 yr. Haddock l m a e off Southwest Nova Scotia appeared 1 rno after eggs were first observed, while cod I m a e were observed in all cruises (Figs. 5 and 6). Only 10 haddock larvae were taken off Southwest Nova Scotia in 1983, while 450 were taken in 1984 (almost all in June) and 1335 in 1985 (in April, May, and June) (Table 2). Cod I w a e (Table 3) were infrequently captured in 1983 and 1984 (total of 15 and 27, respectively), some of which hatched from eggs spawned the previous November, December, and January (Campana and Hurley 1989). The abundance of I m a l cod was highest in 1985, with a total of 408 l m a e taken. Maximum egg and 1 m d station abundances of both cod and haddock were generally higher on Georges Bank than on Browns Bank (Figs. 3, 4, 5 md 6). Although coverage of stations on Georges Bank was sporadic, eggs of both species tended to appear 1 to 2 mo earlier there than off Southwest Nova Scotia.

Discussion Our study confirms earlier reports that Browns Bank is the principle spawning ground of both cod and haddock in Southwest Nova Scotia (Scott 1983; Gagn6 and O'Bsyle 1984; O'Boyle et al. 1984; Koslow et al. 1985; Waiwood and Buzeta 1989). Lower levels of spawning were observed on Baccaro, Roseway, and La Have banks for both species. The marked 1 until the embryo is half way around the yolk, approximately similarity between cod and haddock ichthyoplankton distributhe time of blastopore closure; Stage III, from the end of Stage tions implies that the two species utilize the same spawning I1 until the tip of the tail reaches or could reach the snout; and sites, and that the same physical forces may be influencing the Stage IV, from the end of Stage I11 until hatching. Early egg stages of cod, haddock and witch flounder (@&yp~ocephal~ssubsequent distribution of their eggs and larvae (Campana et a1. H989a,b). Repeated observations of Stage I eggs in the nearcynsglossus) could not be differentiated, and thus were artifishore region are most consistent with inshore spawning, since cially grouped as CHW (cod, haddock, witch). These species Can. J. Fish. Aquut. Sci., Vol. 46, 1989

Can. J. Fish. Aquat. Sci., VoE. $6, 1989


106

Can. $. Fish. &wb. Sci. Val. 4b91989


Can. J. Fish. &wt. Sci., V01. 46, I989


H 08

Can. 9. Fish. Aquat. Sci., Yo/.46, 1989




TABLE2. Length frequency (numbers) of haddock larvae taken off Southwest Nova Scotia and on Georges Bank, by month and year 1983-85. Standard length (mm)

B

2

3

4

5

6

7

8

9

2

-

I0

11

12

13 14 15

16 17 Total

Southwest Nova Scotia

Feb. 83

Mx.83 $83

May 83 June 83 Feb. $4 Mar. $4 Apr. 84 May 84 lun. 84 Feb.85

- - - - 1 - - -

-

-

-

-

- - 1

1 2 -

- - - - - - - - - 1 1 -

1

-

-

- - - - - - - - - - - - - - - - - - - - - - - -

1 - - - - - - - - - -

- - - - - - - - - - - - - -

- - - - a

A

1 5 2 1 2 B - - - - - 1 1 - - - - - - - 25 187 136 58 26 9 - 2 - - - - -

- -

-

- - - - - - -

-

-

- -

Georges B d Feb. 83 Ma.83 Apr. 83 May 83 %an. 83 Feb. 84 Mar. 84 Apr. 84 May 84 Jun. 84 Feb. $5 Mar.85 Apr. 85 May 85 Jun. 85

reported current speeds (Lawrence and Trites 1983; Smith 1983, 1989) are of insufficient magnitude to have carried the eggs from Browns Bank during the 6-d (maximum) stage duration (Mask and Coltsn 1961 ; Page and Frank 1989). However, the magnitude of inshore spawning appeared to be Bow relative to the total. While inshore spawning of cod has been reported previously (Bigelow and Schroeder 1953; Gagla6 and B9Boyle 1984; O'Boyle et al. 1984), the inshore distribution of Stage IV haddock eggs suggests that haddock may also spawn inshore. Note that ealier reports of apparent inshore haddock spawning (McKenzie 1940; Kohler 1960) were based on inconclusive data. There was a marked consistency among the apparent spawning sites for both cod and haddock. Aside from differences in relative abundance, the stage IV eggs of both species were characterized by similar distributions, despite differences in spawning times and associated circulation pattern changes. There was little or no evidence s f interannual shifts in spawning location. If, as Waiwood and Baazeta (1989) have suggested, spawning location sf haddock is linked to sediment type, this may explain the observed interannual consistency. An equally viable explanation is the correspondence between spawning sites and bottom topography, which is itself correlated with sediment type. Apparent geographic shifts in spawning Iscation, from west to

east, within a spawning season, were consistent across years, and were probably linked to patterns in vernal warning (Brinkwater and Trites 198%).A similar trend in flatfish spawning on the Scotian Shelf was reported by Neilson et al. (1988). Reexamination of the cod egg data presented by Gagn6 and OqBoyle (1984) suggests that the same may apply to cod along the entire Scotian Shelf. The time of peak spawning for cod (April) and haddock (April-June) off Southwest Nova Scotia is similar to that reported elsewhere for eastern Scotian Shelf stocks ( G a p 6 and O'Boyle 1984; O'Boyle et al. 1984). It is also consistent with estimates of peak spawning activity derived from observations of spawning fish (Scott 1983) and examination of otolith microstructure (Campana 1989). However, our data indicate that haddock spawning is more prolonged than was previously described. Further, the timing of peak spawning varied among years, occurring in each of the months April through June. The source of these interannual differences is not immediately evident, nor were similar variations observed in relation to cod spawning. God spawning was usuaHIy initiated earlier than that of haddock, but the lag between their peak times was not always of the same duration (0-2 mo). While this study was not designed to examine any contribution by fall spawners (Gagn6 and 07Boyle1984), some fall progeny were evident among the


TABLE3. Length frequency (numbers) of cod 1mae taken off 'fouB%%we$t Nova Scoh and on George$ Bank. bv mom& a d vear 1983-85.

Southwest Nova Scotia

MU. 83 Apr. 83 May83 Ju~a.83 k b . 84 -

k b . 83

- -

- Mw.84 - - APE.84 - 1 May 84 - - Jm.84 - 1 Rb.$5 - 1 2 Ma.85 - - 4 Apr. 85 - 4 59 May 85 Jun. 85

-

-

5

- 2

38

7

Feb. 83 Mar. 83 A p . 83 May 83 Jun. 83 k b . 84

Ma.84 Apr. 84 May $4 Sun. 84 Feb. 85 Mu*$5 Apr. 85 May 85 kn. 85

larvae collected in this study. Peak spawning on Gesrgcs Bank wewed 1-2 rno earlier than on Browns Bank fm both species, in keeping with other published findings (Grosskin and Henet id. 1987). wemuth 1973; Colton et al. 1949; Sh I n t e r m u d md intespcific c o m p ~ s s n of s egg and 1md production are beyond the scope of this paper, m d in m y ease, have k e n addressed elsewhere (Cmpma et aH. 1989~).However, m the basis of visual inspection of the data, there a p p m s to be little evidence of either synchrony in relative abundmee or exchange of ich&yopl&ton between Browns a d Georges banks (Sn'dh and hfor8e 1985; pmgr and H d e y 1986).

We sincerely thank the many individuds involved in the collection of the smp%es,including the officers md crew of the JA& Halaam&, but particularIy Jim Reid for dl his efforts. T h d s &o gas to the staff sf Maine Research Associates for sorting md identification services, Lou Van Gue1pn and the Huntsman Marine Science Centre for training, advice, and c o ~ ~ ick&yspl&on n g identifications, M.Fowler for editing the volumes of data, P. Shpson for msistmce in the data analysis and S. Hme1 fm preparing the figures. We appreciate the ccsnstmctive reviews of $BHB earlier draft of this manuscript by K. T. F r d , K. G. Waiwwd, R. N. B'Boyle, md an monymous reviewer. Can. Fish. Aqwt. Ssi., Yo&.46, 1989 af.

References BIGELOW, H.B., AND W. C. Smomm. 1953. Fishes sf the Gulf sf Maine. U.S. Hsk Wildl. Sew., Hsk. Bull. 53, 577 p. CAWANPI, S. E. 1989. Otolith m i c r a s ~ scf ~ Emd gad& b the Gulf of Maine, with inferences on early life historyoCan. d. k l - 67: 14011418.

C M ~ A ,S. E.,AND Pa C. F. HWY.

1989. An age- md temperaturemediated gmwh model f a cod (Gadusmrhua) a d haddock (Mebansgmmmm aegiefim) larvae in the Gulf of Maine. Can. S. Hsh. Aquat. Sci. 46:6m-413. CAF~IPANA, S. E.,S. J. S m , AND P.C. F. HHBTUY. 1989a. An age-structured index s f cod Imd drift md retention in the w a r s off sf Southwest Nova Scotia. Rapp. P.-V.R 6 n . Cons. Int. Explor. Mer 191:50-62. 1989b. A drift-rekntiond t h o b m y for l m d kaddwk ( M e h m g r m d on Bmms Bank. Can. J. Fish. Aquat. Sci. K, P. C. E H ~ YP. ,A. KOPLW, F. H.PAGE AND P. C . S m . H989c. Spawrivd iPnd abundance sf young cad (Gadas

mthw) a d haddock ( e h n s g r m u s aeglefinw) as indicators sf paclass st~~mgkh. Cm. J. Fish. Aquat. Sei. 46(%upp1.1): (This issue). COLTON, Jw., J. B., W. G . S m , A. W.KENDALL, JR., P. L. M.P. FAHAY. 1979. Principal spawning areas 2LWa times sf Cape Sable to Cape Hatteras. Fish. BdI. 76: 9 11-9 15. D m w p a m , K.F. ;., AND %a. W. T R ~1987. . Monthly mans of temper md salinity in the Scotim Shelf region. Cm. Tech. Rep 1539: iv + 101 p. SSON, E.1878. Embryonicdevelopmentsffive s c i e s of gadoid fishes in Icelaundic waters. f i t Fiskideilh 5: 1 4 .


GAG&,.I, A., AND R. N. 09BonE. 1984. 73-1,timing of cod spwnhg on the Scotim Shelf. p. 501-517. In E. D d ,D.S. Dmielssen, E. Moksness, a d P. Solemdal [ed.] The propagation of cod Gadus morhua L. Rodevigen Rapprtsm 1. G R Q S S LM. ~ , D., AND R. G. H E N N E M U1973. ~ . Spwnhg stock and other factom ~lelatedto recruitment of haddock on Gemges Bank. Rapp. P.-hr. R6un. Cons. Iwt. Explor. Mer 194: 77-88. H a w s , R. E. S., AND %I. B.VWYKOV.1954. Raldisn between feeding and the sexual cycle of the hddoek. J. Fish. Ras. B o d Can* 11: 535-542. KOHER, A. C. 1960. The growth, length-weight re.e8ationship,md maturity of haddock (Meiamgrkam~s6aegJefiiaus L.) from the region d Lmkeprt, N.S. I. Fish. Res. Board Can. 17: 41-60. KOSLQW, 9. A., S. BHPAULT, J. DUGAS,AND E PAGE.1985. hatomy of m apparent year-class fllilm:the early life history sf the 1983 Browns BstnHh haddock (MelanogrammesssregBefinus). Trms. Am. Fish. Sw- 1 14: 478-

O'BOYLE, R. N.,M.S I N ~ L R. ~J* ,CONOVER, K. H. I W w , AND A. C. KOHLER. 2984. Temprd md spatial &s~butionof ieh~yopldtorscornrnwities sf the Scstiim Shelf in relatiow to biologicd, hydrological, md physiographic features. Rapp. P.-V. R6un. Cons. Int. Expior. Mer 183: 27-40. 2989. Spawning time and egg duration in west Adantic. Can. J. Fish. Aquat. Sci.

PFBRY,R. I., AND HUWY. 1986. Circulation and potential ichthpplankton d s p r s d in the Gulf of Mdme, Browns md Gmges Bank m s . CMSAC Res. Dm. 86137: 16 p. S e w , J. S . 1983. Inferred spawning weas a d seasons of groundfishes on the Scotim Shelf. Gm. Twh. Rep. Fish. Aquat. Sci. 1219: iii 14 p. S W B R Y ~ O %I V. , Po1971. On haddock spawning in the Northwest Atlantic m a . Twt. C o m . Noraw. Atlmt. Fish. R d h k 1991, Part ID:83-91. SHERMAN, K.,W.G . S M ~J. R. , G m , E. B. C o r n , M. S. BEW, K. A. 489. M m n , rn I. R. GWLET. 1987. ~ p l ~ b production o n md the fisheries LAWRENCE, D. S:, AND R. W.TRIES. 1883. Surface oil spill trajectory modellof the wortheastem shelf, p. 268-282. %pa: R. H.Backus [ed.] Gesrges ing for Georges and Browns Banks. Can. Tech. Rep. Hyckog. Ocean. Bank. The MlT Press, Cambridge. Scl. 29: iv f 38 p. S m , PaC. 1983. The ma^ and seamapnd circulation off southwest Nova ~WARAK, R. R., AND J. B. COLTON, 9 ~ 1961. . Distribution of fish eggs md Scotia. 1. Phys. Ocemogr. 13: 1034-1054. larvae, temperature md salinity in the Georges Bmk43ulf d Make m a , 1989. Ckcdattirpn md dispersion on Brwrss Bank. Cm. 5. Fish. 1953. U.S. Fish Will. Serv., Spec. Sci. Rep. Fish. 398: 1 4 1 . &anat. Sci. 4-6: %3!+559. D. IE, AND L. A. FROST.1985.Csmpaative mopho10gy, ~emomdity~ S m , W. G . , AND W. W. MORSE.1985. Retention 0%Imd haddock Mehpeand a key to planktonic fish eggs from the Nova Scotim Shelf. Can. 9. sgmmmw oeglcfinm in the Georges Bad region, a gym-influend Z.001. 43: 246-257. M c m m , W. A. 1940. The spring haddock ''mn,17Jordan H h w , N.S. ,AND D. 9; Duwm. 1982. An evduation of Hsh. Res. Board Can. Atlmt. hog. Rep. 28: 9-13. NELSON, B. D., E. M.DEBLOIS, AND P. C . E HWE'Y. 1988. Stmk s m c m niques. I. Cons. Int . Explot, Mer 40:226-236. sf S c o h Shelf flatfish as inferred h ~ ichthyopl~ton m s w e y data md W m m ~ K. , G . , AND M.-I. BKZETA. 1989. The reproductive biology of the geographic distribution of mature females. Cm.L Fish. AquatoSsi. Southwest Scotim Shelf hd8sck r m u s mglefinus L.).Cm. L Fish. Aquat. Ssi. 46 (Suppl. I): 45: 1694-1685.

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Can.J. Fish. A q u . k i . , V.1. 46, 1989