This paper not to be eited without prior referenee to the author. Some Preliminary Results from Tagging of Lumpsucker (Cyc10pterus 1umpus) 1966

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1 This paper not to be eited without prior referenee to the author. C.M.1967/F:23. Demersal (U) Committee. Some Preliminary Results from Tagging of Lumpsucker (Cyc10pterus 1umpus) 1966 by OIe Bagge. In April 1966 a number of Lumpsucker (Cyclopterus lumpus) were tagged in the southern part of Kattegat at Sjool1ands Odde. In all 18 individua1s were tagged. Ti11 September 1st, 1967 a total of 161 individuals have been reeaptured, or 10.3%. Purpose. The above-mentioned tagging experiment was made with the fol1owing purpose: 1. Ta find out where the lumpsueker stays during winter, 2. To investigate whether the lumpsucker returns to the same spawning place the following year, and consequently whether they spawn more than onee, 3. If possib1e to get some information about the growth. Tagging Experiment. I. Liberation. a - Tags. Great white Petersen discs (diameter 25 mm) were used; by means of a titanium wire these dises were fixed on both sides of thc posterior part of the first dorsal fine b - Material. All individuals in the experiment were caught in special set nots used for catching lumpsucker (mesh size 140 mm). The nets wore plaeed near tho shore; the depth ranging from 5 to 10 m. The tending of the nots and the tagging was adjusted so that no fish were more than one minute on deck. This is important, bccauso they will otherwise float belly up after the tagging. All individuals usod wore in the stage of maturity just before spawning (V-VI); none were spent. From Table I it appears that in all 1122 femalos wore tagged, mean length 42.3 cm, and 446 males, mean length 36.0 cm. The - 8mall number of males is due to the fact that they, beeause of their smaller size, to a cortain extent pass through the nots. Ir. Recaptures. a - Recaptures of males and fomales. From Table I it will be seen that until September 1st, individuals or 10.3% were caught; the total recaptures of males were , and of female~ in the same period. The first year after tagging 13.2% males and 7.8% females were recaptured, and the second year 0.7% males and 1.1% females. The differenee between males and females in the total recaptures is signifieant; u = This is also the oase when compuring tho reeaptures of males und females for only the first year; u thon being

2 - ~ - There is, ho~ever; no significant difference in the captures of males and fe~ales the second year, u being , but the nubbers are paori 1t is possible that the natural mortality is greater for females than for males. The reason for this may be that the females. are subject to damage when spawning and are exhausted after production of the great amount öf eggs. It ought to be mentioned that dead females are often captured in bottom trawl in spring ahd also that two of the tagged females were captured in bottom trawl, half decayed~ The difference found mny also be due to the haies remain1ng in shnllow waters for a longer ti~e ~fter spawning than the females, among other things to guard the eggal Therefore the males are more exposed to be captured. This also appears from Table 11, which sh6ws recaptures of males and females far each calendar month. b - Migrations. On Figg. 1-6 the recaptures of males and females are plotted according to month for recaptures in the first and second year after tagging. From Figg. 1-4 appears that males as weil as females after tagging have continued their migrations along the shore and reached into the western as weil as the central Baltic. It can be supposed that the lumpsuckers in spring migrate along the shore until spawning starts. However, it mu~t be taken into account that amigration which possibly had ceased might be resumed because of capture and tagging. The first-mentioned possibility must be considered most likelyas the recaptures the following spring (1967) (Figg. 5 and 6) are distributed in same way. From Figg. 5 and 6 it is further seen that 4 out of 15 (27%) recaptures have taken place at the localities of liberation. All individuals recaptured in the second year were mature. From thisis appcars that thc lumpsuckers, males as weil as females, are able to spawn more than once. Remarkable is the recapture in Skagerrak in Septeober (Fig. 3). The lumpsucker was caught in herring drift net) the depth of the fishing place was 300 n. Further two recaptures were made in bottom trawl near Skagen in March 1967 (Fig. 5). The recapture in Skagerrak indicatcs a pelagic stay in rather deep water duripg spring and winter, (pelagic captures of lumpsucker are mentionod by Bagge, 1964). The two last-mentioned recaptures may indicate a change (before spawning) froo the pelagic stage back to the demersal stage Growth. For' 7 of the 15 recaptures made one year after tagging information about length at recapture (6 females and 1 male) was available. Table 3 shows length at tagging and recaptures (as weil as growth). It shows that growth varies from cm for females, in average 4.0 cm. The single male had grown 2.0 co. It has to be added that the growth estimate is rather uncertain, partly as the lumpsucker on account of its shape is difficult to measure, partly because the individuals recaptured wore mcasurcd by different persons. The growth estimatcd by tagging seoms grcater than tho growth estimatcd by otoliths (Bagge 1964), whioh was per year for males: age group IV 4.43 CO; aga group V 1.11 cm; age group VI 0.99 cm. For femnles the corresponding growth for age group V was 0.71 and far age group VI 1.39 cm.

3 - 3 - Summary. 1. A small number of females than males are recaptured the first-year owing to the greater mortality of females on account of the exhaustion from spawning and their leaving the spawning place immediately after spawning. The males remain catchable to a certain extent during summer. 2. Recaptures in Skagerrak in drift net and near Skagen in bottom-trawl indicate a pelagic life during winter over deep water. ~ Captures the following spring of mature tagged individuals in the same area as the tagging 10ca1ity show that the lumpsucker is ab1e to spawn more than once, and that it returns to the same area. ~ Growth per one year is found to be 4.0 cm for fema1es (6 individua1s), one male had grown 2.0 cm~ References. Bagge, OIe, 1964: "Same observations on the bio10gy of the 1umpsucker (Cycloptcrus lumpus)."c.m Baltic-Belt Sea Committee No. 150

4 Table I. Number tugged Mean length em Males Females Total ,0 ( ) ,3 ( ) 18 Number recaptured ls;t 2nd year 3 (0.70%) Total 62 (13.9%) 12 (1.1%) 99 (8.8%) 15 (1.0%) 161 (10.3%) Table H. Number reeaptured.by lllonth end sex. April Mu1es Fema1es h Numbei- peroent ", '" Number p~rcent May June Ju1y August September October November December January 1967 February Mareh April May Tab1e 111. Length when tagged (ern) Females Length when reeaptured (em) Mean Growth (ern) Ha1es

5 ;H APRI L} MAY :"". 55 H----y--:~ 9 L ::...,. APRIL} MAY öd 55 H-,._-.;:::,

6 57 JUNE er... JUNE 1966 x JULY AUG. öd Fie. 4.

7 57... MAR} APR J8{ MAY?9.Ä. MAR APR. 00 ",'... [~~ip:\,:'..5\,l...i ( / "; '...L.,~..... A, _ _ 7 ~) (.= \,.'..,) /....."'.. tj :.:d'j