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No. 38. An Equation for the Depth Distribution of Deep-Sea Zooplankton and Fishes By

R. J o h n s t o n Marine Laboratory, Aberdeen

That the distribution of animal life in the deep of zooplankton is scarce and, being based on net hauls, ocean is governed by depth and primary productivity does not afford accurate estimates of absolute abund­ has been argued by Bogorov (1960) and Yashnov ance. The relative abundances for one gear and one (1960). The results of deep-sea expeditions have made ship are however of considerable value and Table 1 possible a reasonably full description of abyssal zoo­ (with Appendix A) contains most of the available plankton and other animals and their relationships published results. As the logarithm of zooplankton with the environment. Since this environment pro­ abundances seemed to yield approximately straight vides very uniform living conditions it is likely that lines when plotted with the depth (or mean of depth on the whole distribution with depth will follow a range), cf. Bogorov and Vinogradov (1955), the rela­ uniform pattern. Such a pattern when expressed ma­ tionships giving the logarithm to the base 10 of the thematically could be useful in the study of zoo­ expected abundance of animals (log N) at a given plankton distribution and abundance with depth. depth (z metres) were derived by the method of least Quantitative information on the depth distribution squares and are listed in Table 2.

T able 1. Dependence of animal life on depth (For details see Appendix A)

m 1 2 3 4 5 6 7 8 9 0 11-7 - 0-50 - 0-50 497-6 0-100 1650 - 378 54,000 234 100 110 - 50-100 - 50-100 320-3 100-200 -— 144 29,800 200 9-6 - 100-600 221 100-200 246-6 236 1300 — 3401 300 7-3 - 45 175 200-500 - 200-500 - - 400 130 -- 105 2734 228-0 155 1450 - 500 10-4 4360 - 130 500- - 500- - 500- 600 8-8 2820 600- 150 1000 - 1000 - 1000 800 6-6 2550 1000 207 1154 59-3 105 740 5-4 1000 5-3 3350 77 77 1000- 1000- 1000- - 1000- 1200 4-6 2850 1000- 41 4000 2000 2000 - 2000 1400 4-6 2150 2000 39 303 21-8 58 290 1-6 1600 5-0 1150 45 69 ----- 1800 4-8 350 - 31 ----- 2000 3-8 1400 - 45 ---- 2000- 2200 2-8 1330 - 26 ---- 3000 2400 1-9 1050 - 28 ---- 0-8 2600 1-4 450 - 6 _ 2000- 2000- - 3000- 2800 1-2 200 - 3 - m o 4000 - 4000 3000 0-9 690 - 5 _ 9-3 34 135 0-3 3200 0-7 980 - 2 - 4-6000 -- 4000- 2-64 5000 4000 0-1 600 —— — 6-8000 —— 01 0-48 218

APPENDIX A Table 2. Data used in Table 1 : Animal abundance and depth 1. H.M.S. “ Research” , 1900, area sampled 47°29'N to 1. log TV = 1-1974-0 0004217 « 46°43' N y 8 18'W to 7°17'W in the Bay of Biscay, vertical hauls, 2. log TV = 3-6302-0 ■0002835 z mostly 2-5 hauls each range, mesoplankton net 36 or 45 meshes 3. log TV = 2-228 -0- 0004426 z per inch for which no major differences in catching power were 4. log TV = 2-5168-0- 0006035 Z observed. Volume of 100 m haul = 25■ 53 m3. Number of cope- 5. log TV = 3-536 -0 ■0004353 « pods (all species together) per haul (recalculated in metres from 6. log TV = 2-3738-0 0004050 Z fathoms), Farran (1926). 7. log TV = 2-324 -0 ■0002912 2 2. Deep-sea fishes, weight of fish (grams) per haul based on 8. log TV -- 3-230 -0 ■0004574 i Vaillant, 1888. 9. log TV = 0-980 -0 0004391 z 3. Weather Ship ‘M’. 1948-1949, Norwegian Sea, Nansen closing net 40 vertical hauls each range. Volume of 100 m haul where TV is the estimated abundance of animals (see Appendix A), 38-5 m3. Complete analysis of numbers of each plankton species and z is the depth (or mean depth range) in metres. by subsample recalculated as equivalent number of C.finmarchicus stage V, after Østvedt (1955). 4. Western Atlantic Ocean. Horizontal tow, Stramin net, Where possible, groups of results have been pooled mean of 9 hauls each depth. Volume of haul 104 m3/hr. Displace­ in an effort to remove, to some extent, variations due ment volume and detailed analysis. Leavitt (1938). to season and to vertical migration. 5. NW Japan Sea. Calanoids, number per m3, Brodskii (1955), Except for the western Atlantic Ocean (4) and omitting surface values. 6. Kurile-Kamchatka Trench. Plankton, dry weight in mg/m3. tropical waters (7) which are perhaps ecologically Zenkevitch and Birstein (1956). distinct from the others (see Yashnov, 1960), it is 7. Tropical waters. Plankton, dry weight in mg/m3. Bogorov evident that the equations (1, 3, 5, 6, 8, 9) are of a (1957). uniform type with a fairly constant slope of 0-00042. 8. Boreal waters. Plankton, dry weight in mg/m3. Bogorov (1957). 9. North Equatorial and Canary Currents. Plankton, dry For trawl-caught deep-sea fishes (equation 2), the weight in mg/m3. Yashnov (1960). average food requirement can be calculated, using

Table 3. Deep-sea echinoderms Echinoderms. (Results of “Talisman” and “Blake” together) (After Perrier, E. (1894) and Perrier, R. (1901))

Stelleridae Holothuridae

Catch Catch (m) Hauls Individuals Hauls Individuals per haul per haul

1 0 0 .... 11 30 2-7 _ _ CM O O O Q 33 217 6-6 17 m 2-2 200- 3 0 0 .... 29 212 7-3 --- 300- 400.... 18 48 2-7 13 6 0-5 400- 500.... 7 57 8-1 --- 500- 600.... 12 32 2-7 21 36 1-7 600- 700.... 5 20 4-0 --- 700- 800. .. . 5 6 1-2 23 11 0-5 800- 900... . 8 33 4-1 - - - 9 0 0 -1000.... 6 23 3-8 21 64 3-0 1000-1100.... 7 49 7-0 -- - 1100-1200.... 9 60 6-7 15 63 4-2 1200-1300.... 8 95 11-9 --- 1300-1400.... 4 20 5-0 18 63 3-5 1400-1500.. . . 7 41 5-9 --- 1500-1600... . 4 10 2-5 14 42 3-0 1,6,00-1800. . . . 5 18 3-6 3 0 0 1800-2000.... 2 5 2-5 6 34 5-7 2000-2500.... 23 154 6-7 27 53 2-0 2500-3000.... 1 13 13-0 7 0 0 3000-3500.... 3 5 1-7 5 13a 2-6 3500-4000.... 2 10 5-0 4 5 1-25 4000^500.... 2 34 17-0 5 40b 8-0 4500-5000.... 2 15 7-5 2 7 3-5

a. - one catch not recorded, taken as 3. b. - one exceptionally large catch (56) taken as 3 (overall average number per haul). 219

60 g food/kg fish/week (Brown, 1957) at 10° G as a large ocean is an essential condition for the inter­ basic maintenance requirement, and a factor of 1-1 pretation of oxygen change in terms of age or water for mean activity resting level. It is assumed that food circulation (Johnston, 1960). requirement (F), like respiration, will be subject to the effect of temperature on metabolism, e. g. Q,10 = References Bogorov, V. G., 1957. “Regularities of plankton distribution in the north-west Pacific”. Proc. UNESCO Symp. phys. Oce- \ = 2-5 but independent of pressure effect, anogr., Tokyo 1955, pp. 260-276. Bogorov, V. G., 1960. “Productive regions of the oceans”. ICES / T i ~ T o C. M. 1960, Doc. No. 137 (mimeo.). Bogorov, V. G., & Vinogradov, M. E., 1955. “On the zooplankton giving in the north-western part of the Pacific Ocean”. Dokl. Akad. Nauk, U.S.S.R., 102 : 835-38 (in Russian). log F = 1-468 - 0-0003668 z (g food/kg fish/week). Brodskii, K. A., 1955. “On the vertical distribution of copepods in the north-western Pacific Ocean”. Spec. sei. Rep. Fish. U.S. This curve has a similar slope to that for zooplankton Fish Wildl. Serv., No. 192: 1-6. relative abundance. Brown, M. E. (Ed.), 1957. “The physiology of fishes” . Academic Press Inc., New York, 446 pp. Starfishes and holothurians form the greater mass Denton, E. J., & Marshall, N. B., 1958. “The buoyancy of bathy- of epifauna in the Azores region and records of catches pelagic fishes without a gas-filled swim-bladder” . J . mar. biol. are listed in Table 3. There is no marked trend in Ass. U .K ., 3 7 : 753-67. quantity with depth - a conclusion supported by nu­ Farran, G. P., 1926. “Biscayan plankton collected during a cruise merous scattered observations in the reports of the of H. M . S. ‘Research’, 1900. Part X IV . The copepoda” . J. Linn. Soc. (Zool.), 3 6 : 219-310. “Galathea” and other expeditions. This uniformity Johnston, R., 1960. “Oxygen distribution and the renewal of in the abundance of epifauna irrespective of depth North Atlantic deep water”. ICES C. M. 1960, Doc. No. 185 suggests that eventually, in one form or another, much (mimeo.). Leavitt, B. B., 1938. “The quantitative vertical distribution of the same amount of “food” reaches the bottom what­ macro-zooplankton in the Atlantic Ocean basin”. Biol. Bull., ever the depth, excluding of course waters where depth Woods Hole, 74 : 376-94. or turbulence permits direct or almost direct feeding Perrier, E., 1894. “Echinodermes”. Expéditions scientifiques du on plant production. “ Travailleur” et du “Talisman” , pendant les années 1880 -1883. Masson, Paris. It therefore seems probable, from the similarity Perrier, E., 1901. “Holothuries”. Expéditions scientifiques du between estimated fishfood distribution and that of “Travailleur” et du “Talisman”, pendant les années 1880- the observed macroplankton, that deep-sea fishes are 1883. Masson, Paris. primarily dependent on pelagic food and only to a Vaillant, L., 1888. “Poissons”. Expéditions scientifiques du “Travailleur” et du “Talisman” , pendant les années 1880 small extent on the bottom epifauna. — 1883. Masson, Paris. This depth relationship also lends material support Yashnov, V. A., 1960. “Plankton of the tropical Atlantic Ocean”. to Yashnov’s statement that “the identity in the ICES C. M. 1960, Doc. No. 163 (mimeo.). vertical distribution of zooplankton mass in ecologi­ Zenkevitch, L. A., & Birstein, J. A., 1956. “Studies on the deep- water fauna and related problems”. Deep-Sea Res., 4 : 54 64. cally identical areas is not likely to be accidental”, Ostvedt, O.-J., 1955. “Zooplankton investigations from weather (Yashnov, 1960). ship ‘M’ in the Norwegian Sea, 1948—49”. Hvalråd. Skr., A uniform animals/depth relationship applicable to No. 40: 1-93.

Discussion1) Several speakers in the discussion commented that gear - observations of fish in bathyscaphe descents Johnston’s equations did not allow for the many ob­ demonstrated this. He thought that local abundance servations of layers of zooplankton and maxima at of food, such as debris from land, was important for intermediate depths, to which Dr. Fraser replied that deep-sea fish. Professor Bernard agreed with Dr. Bruun Johnston had used only averages of plankton counts about bathyscaphe observations ; he said that dredging and that they would correctly represent average con­ on a muddy bottom from the “Calypso” produced ditions. Dr. Bruun said that the numbers of deep-sea nothing, but photographs of the bottom showed many fish had been grossly underestimated from hauls by worms. He also mentioned the importance of coccoli- past expectations using very inefficient sampling thophorids and ciliates in production in some areas. Dr. Laevastu said that, although Johnston had left *) In the absence of the author this paper was presented by out the boundaries, he had produced a useful mathe­ Dr. Fraser. matical model.