Herring (Clupea harengus) filter-feeding in the dark

Mortality during the egg and larval stages is thought to play a major role in de termining year-class strength of many marine fish. Predation of eggs and larvae is normally considered to be a major factor but the full suite of predators responsible has rarely been identified. Potential predators on a patch of plaice Pleuronectes platessa eggs located in the eastern Irish Sea were mapped using acoustics and sampled by trawl and a plankton multi-net. Gut contents of 3373 fish, crustacea and cephalopods sampled in the area were screened using a plaice-specific TaqMan DNA probe. Herring Clupea harengus and sprat Sprattus sprattus dominated trawl catches and showed high positive TaqMan responses (77 and 75% of individuals tested respectively). Locations of clupeid schools also broadly corresponded with the distribution of fish eggs in the plankton. Whiting Merlangius merlangus were also reasonably abundant in trawl hauls and 86% of their stomachs tested positive for plaice DNA. Species showing lower levels of positive TaqMan response included mackerel Scomber scombrus, poor cod Trisopterus minutus, squid Loligo spp., dogfish Scyliorhinus canicula and weever Trachinus vipera. Nonre activity of all negative controls precluded the occurrence of cross-contamination, and positive reactions from demersal species, such as dogfish and weever, may have resulted from secondary predation. No benthic macro-crustaceans tested positive. Samples of planktonic organisms yielded 13% positive TaqMan reactions, mainly from clupeoid or sandeel (Ammodytidae) larvae, but also included some Malacostraca and Amphipoda. Use of the molecular approach allowed rapid screening of a large number of potential predators of plaice eggs, and the results provide a more holistic description of the predator community than has previously been achieved.

Section: Clupeids As Fish Egg Predatorsmentioning

confidence: 99%

Identification of marine fish egg predators using molecular probes

Fox¹,

Taylor²,

Kooij³

et al. 2012

“…In this experiment, the >g00 pm and >500 pm size-classes were composed of Time after food introduction (min) Several other clupeoid species exhibit both filterand particulate-feeding modes, depending on the size and concentration of available prey. Species that exhibit this feeding flexibility include Alosa pseudoharengus (Janssen 1976(Janssen , 1978, Clupea harengus (Gibson & Ezzi 1985, Batty et al 1986), Dorosoma petenense (Holanov & Tash 1978), Engraulis capensis (James & Findlay 1989) and E. mordax (Leong & O'Connell 1969, O'Connell1972, Hunter & Dorr 1982. These species generally filter-feed when presented with high concentrations of small particles (e.g.…”

Section: Feeding Ratesmentioning

confidence: 99%

Effect of particle size and concentration on the feeding behaviour of adult pilchard Sardinops sagax

Lingen¹

1994

Laboratory experiments investigated the effect of food particle size and concentration on the feeding behaviour of adult pilchard Sardinops sagax. This species employs 2 methods of feeding: filterfeeding and particulate-feeding. Particles of less than 1230 pm total length elicit a filtering response while larger particles elicit particulate-feeding at low concentrations and filter-feeding at high concentrations. Clearance rate during filtering is independent of particle size and concentration over the size range 393 to 1227 pm, with a mean value of 11.78 2 4.91 1 fish-' min-l. This value is 93 % of the calculated maximum clearance rate for flltenng f~s h , Implying that pilchard are highly effic~ent at feedlng over this size range. Particles of less than 206 pm are cleared at reduced rates, with retention efficiency inversely proportional to particle size Clearance rates during particulate-feeding are greater than those for filtering, and increase with increasing particle slze to a predicted saturation value of 46.53 1 fish-' min" Pilchard display size-selectivity during parbculate-feed~ng, preferentially removing larger prey Items. Results indcate that pilchard is primarily a filter-feeder, obtaining the majonty of ~t s food from the smaller end of the size spectrum of available prey Mlcrozooplankton, and to a lesser extent phytoplankton, are major dietary components. T h~s IS in contrast to Cape anchovy Engraulis capenas, which is primarily a particulate-feeder and derives most of ~t s food from the larger end of the size spectrum of available prey. The different feeding responses of these 2 CO-occurring species are discussed w~t h reference to resource partitioning.

“…The mechanism for feeding in the dark is not clear. Herring juveniles Clupea harengus swim faster and adopt a filter feeding strategy when forced to feed in the dark on Artemia nauplii (Batty et al 1986). …”

Section: Growth and Foragingmentioning

confidence: 99%

Estimating the food requirements of striped bass larvae Morone saxatilis: effects of light, turbidity and turbulence

Chesney¹

1989

126

102

Laboratory experiments were conducted to study the effects of food concentration, turbulence and turbidity on growth and survival of striped bass larvae Morone saxatilis. Initial experiments indicated that striped bass larvae could forage and grow well ( G = 0.143 to 0.179 d-l) at food concentrations ranging from 50 to 250 ind I-' of the copepod Eurytemora affinis and that growth was similar on Artemia sp. and E. affinis. Subsequent experiments tested effects of turbidity (50, 100, 150 ppm kaolin), reduced light intensity (2000, 1000, 600, 300 lux) and turbulence, separately, and then reduced light intensity (450, 70, 12, 0.4 lux) in combination with turbidity (150ppm kaolin) and turbulence to determine how these variables moderate food requirements of striped bass larvae. Reducing light or adding turbulence reduced growth and forage rates, while adding turbidity in combination with turbulence apparently ameliorated some of the negative effects of the turbulence. Although growth studies indicated an energetic cost of turbulence, additional experiments comparing weight loss and starvation mortality in turbulent versus non-turbulent conditions showed no significant differences. A comparison of individual growth variability (G) in the turbidity (150 ppm) reduced light treatments and the treatment in total darkness without turbidity or turbulence showed that while average growth rates were positive, a portion of the individuals surviving until 25 d after hatch were either not growing or losing weight. Low light level in combination with turbidity and turbulence substantially reduced survival and growth rate, but even at very low light levels (< 1 lux) and darkness, striped bass were able to survive and grow. Results indicate that previous studies of critical food requirements of striped bass larvae may have overestimated necessary prey levels. Although striped bass larvae are well adapted for growth and survival in highly turbulent, turbid environments, encountering poor feeding conditions in the field is likely to greatly reduce their probability of survival to the juvenile stage.