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Tunicata, Thaliacea)* Rophique Et Dis- E Intertropical ed by sei whale UDC 597.591.132 -Tsusin, No. sopelagiques 45. Feedin g of Fishes on Salps (Tunicata, Thaliacea)* rophique et dis- e intertropical. A.A. Kashkina the vertically Williams) off Biology Faculty, Moscow State University, Moscow 0-327. d'organismes A review of the literature shows that more than 47 fish species belonging to 23 families of 10 orders, Clupeiformes, Salmoniformes, Myctophiformes, Beloniformes, Gadiformes, Bery- ciformes, Zeiformes, Scorpaeniformes, Tetradontiformes, and Perciformes, in different regions of the world ocean feed upon salps. They avoid only their dense surface concentrations. Some fishes feed upon saips during parts of the year when the salps are predominant in the plankton. The salps play a major role in the diet of many fish species of the mesopelagic region on the continental slope, islands, seamounts and elevations where the concentration of salps in plankton in some periods is particularly high owing to local increase in productivity. A moderate amount of information has accumulated during the last two decades for assessment of the utility of salps as fish food. In the late 1960s it was stated that "these organisms are beneficial only to a certain degree: for fishes and their consumption by fishes was interpreted as "more as a shortage than absence of selec- tion in feeding" (Karedin, 1969, p. 137). On the basis of available information on fish feeding on salps, I have attempted to quantify which fishes, in which regions, and to what extent, feed upon these or- ganisms. Data on feeding of fishes upon other tunicates--Pyrosoma and Appendicu- laria--as well as maximum biomass of saips in those regions where the fishes prey on them are also reported. This problem could not be resolved earlier due to the lack of reports on feeding of oceanic mesopelagic fishes as well as on the distribu- tion and quantity of salps in the mesopelagic region. For a long time, it was be- lieved that salps are inhabitants of the upper layers of oceans where they form groups, and their predators in the epipelagic zone were unknown. It was also not known that fishes or other animals are concentrated in large numbers in the areas of dense salp populations. It was repeatedly noted in different parts of the oceans that the fast generating groups of salps replace the other zooplankton (Bigelow, 1908, cf. Foxton, 1966) and fishes move out of these regions. Near the coasts of Morocco, sardine, Sardina pLichardus, leaves areas with large concentrations of saips (Furnestin, 1957, 1970), and herring, Clupea harengus harengus, as a rule, abandon such areas in the North and Norwegian seas (Fraser, 1961; Brattstrom, 1972). Off the California coast, anchovy, EngrauZis mordax, larvae are not found in regions where saips or Pyrosoma are found in more than 50% of the samples; maximum larval conce ntration is found where the plankton consists mainly of copepods (Alvarino, 1980, 1981). These facts provided indirect evidence that saips are not important food. Act ually, salp tissue has a very high water content: 98.3% of live weight (85% in cope-pods) (Riley and Gorgy, 1948) and, similar to other tunicates, the membrane con- t ains mucopolysaccharides (Godeaux, 1965) which is not assimilated in fish digestion. The only organ of salps that has nutritional value for fish is their stomach, the nuc leus, which is often green or red depending on the composition of the filtered food and almost always compactly filled with phyto- and microzooplankton. *Originally published in Voprosy Ikhtiologii, No. 3, 1986, pp. 440-447. 57 ISSNO032-9452/86/0004-0057$7.50/0 © 1987 Scripta Technica, Inc. The study on salp biology showed that they are constantly present in the epi- 2_4 cm long sal' pelagic and mesopelagic zones (Foxton, 1966; Kashkina, 1978) and constitute a large plankton at part of the macroplankton and mesoplankton communities, and can show a sharp in- macro at lesser depths crease in abundance under favorable conditions. greatat7itsa r aasi-f i Z Many fishes in different oceanic regions, together with other animals, catch of Honshu Islanc salps more or less randomly. Among them are: sunfish, Mao mola, in the Norwegian Gadus morhua morhua, in the Barents Sea (Fraser, 1962), Sea (Ehrenbaum, 1936), cod, ofi ng t oi-lef irrnack:d relt I haddock, Melanogrammus aeglefinus, in the Bay of Fundy (McKensie and Homans, 1937)- some flying fishes (species not identified) (Parin, 1967), and tunas in the Central In the regi Pacific (Reintjes and King, 1953; King and Iversen, 1962). According to underwater salps become one observations, in the Honolulu region, juvenile rainbow runner, EZagatus bippinnu- al., 1969; Kared Zatus, adult triggerfish, Alutera spp., and spotted triggerfish, Canthidermis macu- (toge ther with often gulp the salp chains (colonial form) (Hunter and Mitchell, 1967). Zatus, and each increas with the concent Salps are also found in the stomachs of mesopelagic fishes. Salps were found in the 0-100 m 1 Lutken, Diaphus dumerilii in the stomach of CeratoscopeZus warmingi (Bleeker), and cal waters was 9 ArgyropeZecus affinis Lepidophanes guentheri in Gulf of Mexico, off the coast of there are fishes Southern California (Hopkins and Baird, 1977); Diaphus garmani in the Central P aci- in the New Zealand region (Thomp- fic (Nakamura, 1970); and Parapercichthys colias At the Cali son, 1948). Legand and Rivation (1969) reported feeding of mesopelagic fishes on ton during the u salps without indicating the species; in the northeastern Atlantic Ocean (depths of food for the mes fish catch 500-1200 m), salps were found in the stomachs of Alepocephalus bairdii, and Bathylagus euryops. Xenodermichthys copei, Argentina silus The proportion of Salps and p salps in different size groups of these species was 0.7-17.9% of the stomachs with Pentaceros richa salps, or 0.4-23.0% of the total number of prey organisms in the stomachs with salps the Hawaiian ran (Mouchline and Gordon, 1983). elevations and m of the North Pac Sometimes salps in the fish diet can he identified to the species level: Thal- the low plankton Chaetodon unimaculatus, ia democratica was found in the stomach of butterfly fish, due to salps and was found in the stomach of in the Honolulu region (Yount, 1958); Thlea punctata tionary system o from the Irish Sea (Fraser, 1962a); in the Norwegian Sea, when herring, C. harengus, where feeding fi appeared for the first time during the period of observations over Salpa fusiformis zonaria, Pyrosom yshtiks and Rudakova, many years, herring consumed it to a fairly large extent (Pa 1975). At the " 1962). stomachs of boar 70% in February, These isolated observations were subsequently supplemented by more convincing the Hawaiian ran observations and studies. For instance, the frequency of occurrence of salps in 1976), undoubted the stomachs (of the total number of organisms in the stomachs) of Nototheniidae and level of sal- (marbled notothenia, Notothenia rossi marmorata, and toothfish, Dissostichus elegi- noides caught in the area of South Georgia Island from depths of 100-700 m was 1.5- Borets (197 2.0% depending on the place and time of catching (Tarverdieva, 1972; Permitin and radiolarians whip Euphasia superba and benthic gammarids, salps Tareverdieva, 1972). Together with during winter. are the main food for many fishes caught off South Orkney Island from depths of 170- as the common fo4 780 m; in this region, they have maximum importance (frequency of occurrence 51.7%) filter feeders, t (a planktivore), secondary importance (15.1% and 20.7%) for N. Zarseni for N. kempi nuclei, as the ni (prefers benthic animals), and of third degree (a planktivore) and N. gibberifrons skeletons of rad: importance (8.4%) for Trematomus euZepidotus and some other fishes (Permitin and Tarverdieva, 1978). In the stomi living at depths The proportion of salps in the stomachs of rock grenadier, Coryphaenoides ru- 197 9). Like in ( pestris, caught from the continental slope of Iceland at depths of 300-800 m, reached quite rich, inclt 94% (by weight) and 29.8% near Labrador and Greenland; the largest number of salps of the Naska rani was found in fishes from depths of 300-500 m (Podrazhanskaya, 1969). Dense concen- to SaZpa thompsor trations of salps in the North Atlantic were recorded repeatedly, with the maximum population strength in the mesopelagic region, based on the samples of Isaacs-Kidd Salps have 3 (Kashkina, 1978a). trawls in the waters of the North Atlantic Current reaching 2.6/m fic Ocean. The c much higher in some years in the depth of the Ir- Possibly, the salp population is lands, seamounts minger Current as well as near the continental slope of Greenland and Labrador, as masses by the Sot_ the stomachs of grenadiers in this region were almost completely filled with them. Int eraction of tu tic ), created a 1 The largest number of fish species feeding on salps is reported from the Paci- cal conditions ar fic Ocean. For instance, individual schools of mackerel, Scomber japonicus, in the is abundant devel Tartar Strait off Moneron Island above a depth of 200 m changeover to feeding upon po sition in the c 58 .ent in the e pi- 2-4 cm long salps in July-August, which at this time constitute a large part of mstitute a large macroplankton and are found in the stomachs of 21% of the fish; mackerel juveniles v a sharp in- at lesser depths also feed upon small sized salps, however, salps do not have a great significance in the ration of mackerel in this region, and Kun (1954) consid- ers salps as "survival" food. The mackerel larvae (5-10 mm) near the southern tip animals, catch of Honshu Island eat Appendicularia (Oikopleaura sp.), which constitutes up to 20% in the.
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