Planktivorous fish

One example for a chemically defended zooplankton species is the Antarctic pteropod Clione antarctica. This shell-less pelagic mollusk offers a potentially rich source of nutrients to planktivorous predators. Nonetheless fish do not prey on this organism, due to its efficient chemical defense. In a bioassay-guided structure elucidation, pteroenone 37 could be isolated and characterized as the main defensive principle of C. antarctica [82,83]. If embedded in alginate, this compound is a feeding-deterrent in nanomolar concentrations. This unusual metabolite is likely to be produced by C. antarctica itself and not accumulated from its food, since its major food sources did not contain any detectable quantities of 37. 

Fig.1 Generalized pelagic food web [ 13]. The old view of a simple food chain vertical line in this figure) with phytoplankton (mainly diatoms) at the base, herbivorous mesozoo-plankton (mainly copepods) at the second trophic level, and planktivorous fish has been extended to a pelagic food web including nanoplankton (<20 pm), picoplankton (<2 pm), and their protozoan feeders lower left). Herbivorous tunicates and jellyfish as primary carnivores also play a role, as do mixotrophic flagellates. The main pathway of energy flow depends on the nutrient scenarios [13]. DOC=dissolved organic carbon, HNF=heterotrophic nanoflageUates. From [13] with permission of Kluwer Academic Press...

There is a strong interannual variation in the lipid concentration in the flesh of planktivorous fish such as anchovy, kilka and sprat, which is governed by the varying abundance of the plankton (Shulman, 1972b, 1996 Luts and Rogov, 1978 Luts, 1986). 

Bray, R.N., Purcell, L.J. and Miller, A.C. (1986). Ammonium excretion in a temperate reef community by a planktivorous fish, Chtomis punctipinnis (Pomacentridae), and potential uptake by young giant kelp Macrocystis pyrifera (Laminariales). Marine Biology 90,327-334. 

Lucas, J.S., Hart, R.J., Howden, M.E., and Salathe R., Saponins in eggs and larvae of Acanthaster planci (L.) (Asteroidea) as chemical defenses against planktivorous fish, J. Exp. Mar. Biol. Ecol., 40, 155, 1979. 

Montgomery, J.C., Pankhurst, N.W., and Foster, B.A., Limitations on visual food-location in the planktivorous antarctic fish Pagothenia borchgrevinki, Experentia, 45, 395, 1989. 

As a result, the commercial fish catches decreased this especially refers to the planktivorous fishes that are food competitors of M. leidyi such as the anchovy Engraulis encrasicolus ponticus, the Mediterranean horse mackerel Trachurus mediterraneus ponticus, and, to a lesser extent, the sprat Sprattus... 

No examples of consumption of adult representatives of rapa whelk by fishes or other hydrobionts are known only its planktonic larvae may be consumed by planktivorous fishes. Rapa whelk is an active predator that consumes valuable representatives of benthos. It inserts significant changes into the structure of bottom biocoenoses and often is the dominating species of the bottom communities being itself an ecological dead-end. Therefore, its commercial extraction is extremely important for reducing the pressure on bivalve mollusks. 

Domoic acid exposure to mammals occurs orally in a matrix of shellfish to human consumers, planktivorous fish and benthic invertebrates to marine mammals, and perhaps zooplankton and chained diatoms to whales. Analysis of the consumed mussels from the 1987 exposure indicated that 1 mg/kg was sufficient to induce gastrointestinal symptoms and 4.5 mg/kg could induce neurological effects in humans (Perl et al. 1990). Experimental studies in monkeys, rats and mice have utilized oral gavage, intraparenteal, and intravenous exposure routes and determined that oral gavage is about ten times less effective that the other routes of exposure (Iverson et al. 1990). Humans appear much more sensitive than either monkeys or rats, which when dosed orally have no observable adverse effect levels (NOAEL) at 5 and 28 mg/kg, respectively. Experimental animals have permitted evaluation of different dose scenarios. A daily NOAEL oral gavage of domoic acid to rats for... 

Durbin, E. G., and Durbin, A. G. (1981). AssimUation efficiency and nitrogen excretion of a filterfeeding planktivore, the Atlantic menhaden, Brevoortia tyrannus (Pices Clupeidae). Fish. Bull. (NOAA) 79, 601-616. 

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