Effects of turbidity and zooplankton availability on the condition and prey selection of pike larvae (original) (raw)
Related papers
Does the zooplankton prey availability limit the larval habitats of pike in the Baltic Sea?
Estuarine, Coastal and Shelf Science, 2010
The objectives of this study were to (1) investigate whether the availability of suitable zooplankton prey limits the distribution of the coastal larval areas of pike (Esox lucius) in two archipelago areas of the northern Baltic Sea and (2) compare the availability of zooplankton prey in spring between different types of coastal littoral habitat. According to the results, reed belt habitats formed by Phragmites australis constitute hot spots for zooplankton prey in the coastal ecosystem. During the spring, reed-covered shores of the inner archipelago maintained more than 10 times higher densities of copepods and cladocerans, the preferred prey for larval pike, compared to the other studied shores. Temperature conditions were also most favourable in the reed belt habitat. Thus, the reed belts of the inner and middle archipelago were shown to form the best habitat for larval pike in the coastal area of the northern Baltic Sea, and this was also the only habitat where pike larvae were found. Our results suggest that the poor survival and recruitment of pike in the outer archipelago, however, cannot exclusively be explained by sub-optimal feeding conditions of the larvae. There are also other important factors, presumably connected to the exposure to the open sea, that affect the distribution of the pike larvae. Our results, however, highlight the importance of sheltered coastal reed belt shores as reproduction habitat for spring-spawning fish in the northern Baltic Sea. Further, this study disproves the assumption that the seaweed bladder wrack (Fucus vesiculosus) forms a reproduction habitat for pike in the coastal area.
Growth of pike larvae: effects of prey, turbidity and food quality
Hydrobiologia, 2013
We studied experimentally the effects of turbidity and prey composition on pike larval growth and hypothesized that pike larval growth varies with turbidity and food quality. We reared the first-feeding pike larvae (Esox lucius) in laboratory tanks with (1) clear or (2) turbid water provided with zooplankton rations from (3) an inner and (4) an outer archipelago site. The sites differ in physical features, salinity, eutrophication status, zooplankton community structure and density. Pike larvae showed the highest weight increase in clear water with zooplankton from the outer site and the poorest weight increase in turbid water with zooplankton as prey from the inner site. Our fatty acid analysis revealed that unsaturated fatty acid levels were highest in the outer site. The relative percentage of copepods was also higher in the outer site. This study supports the hypothesis that turbidity weakens the ability of pike larvae to capture certain prey. Further, zooplankton community composition matters in turbid water, but is not a primary factor in clear water.
Marine Ecology Progress Series, 2008
Eutrophication is a large problem in many marine and brackish-water areas. One of the consequences is algae-induced turbidity affecting visually feeding organisms, and behavioural changes of fish and other animals are common in turbid water. The aim of this study was to compare the performance of larval pike Esox lucius in turbid and clear water. We experimentally studied habitat choice, prey attacks and swimming activity of newly hatched larvae in the presence of a predator and competitors in relation to algae-induced turbidity. Our results demonstrated that the larvae spent less time in vegetation, performed more prey attacks and spent less time swimming in turbid water than in clear conditions. The presence of competitors increased the number of prey attacks, while the presence of a visual predator decreased the number of attacks. We also showed that pike larval weight was lower in high turbidity than in low turbidity. Our results show that algae-induced water turbidity affects both direct (i.e. feeding and habitat choice) and indirect qualities (i.e. weight) of pike larvae and may therefore affect larval survival and potentially even recruitment into the population.
Prey capture of pike Esox lucius larvae in turbid water
Journal of Fish Biology, 2010
Pike Esox lucius larvae captured fewer calanoid and cyclopoid copepods in turbid than in clear water, whereas no differences were detected in feeding rates on Daphnia longispina. Decreased capture of copepods may lead to lower growth and survival of E. lucius larvae in turbid areas, in particular, if cladocerans are scarce.
Marine Biology, 2007
The structure of the habitat is usually crucial for growth and survival of young life stages. Presently, some nursery areas of Wsh larvae are changing due to eutrophication, e.g. due to enhanced growth of ephemeral Wlamentous algae at the expense of perennial species. We studied the inXuence of two habitats, one with Wlamentous algae (Cladophora glomerata) and the other with bladder wrack (Fucus vesiculosus), on habitat choice of pike larvae (Esox lucius) in the absence/presence of a predator or a competitor. We further tested whether the habitat choice is adaptive in increasing survival under predation threat. In contrast to expectations, pike larvae preferred the habitat with ephemeral Wlamentous algae to the bladder wrack, thriving in clean waters, independent of the presence/absence of both predator/competitor. In addition, the survival of the larvae was higher in the Wlamentous algae in the presence of predators, which suggested that the habitat prefer-ence of the larvae was adaptive. The structure of the bladderwrack habitat was probably too open for newly hatched larvae, which implies that F. vesiculosus and other large brown algae are not as important refuges for young larvae as previously thought.
Estuarine, Coastal and Shelf Science, 2011
The pikeperch (Sander lucioperca (L.)) is an economically important fish species occurring in the fresh and brackish waters of Europe. To evaluate the distribution and extent of the reproduction areas in the northern Baltic Sea, a field survey was carried out in two separate coastal areas. Presence/absence data were used to develop a geographic information system (GIS)-based predictive spatial distribution model, where high resolution raster maps of the focal environmental variables and a logistic regression equation were used to predict the probability of larval occurrence. The results indicated that the pikeperch reproduction areas are located in the innermost archipelago zone where high water turbidity best explained their presence. Turbidity was related to several other variables such as fetch and depth. Contrary to our preliminary hypothesis, surface water temperatures measured during the survey had no significant effect in the model due to the low spatial variation in the measured values. Since turbidity is possible to determine by remote sensing methods, the probability maps can be cost-effectively extended to more extensive coastal areas with proper validation.
Aquaculture Research, 2010
The e¡ect of water turbidity on the prey selection and consumption of the young-of-the-year (YOY) pikeperch in the planktivorous feeding stage was studied. Attention was paid particularly to the question of how the food selectivity depends on the size of YOY pikeperch and how the turbidity a¡ects feeding in different size classes. Studies were carried out in ponds of two ¢sh farms in Estonia over 4 years. Small cladocerans were the most preferred prey in the smallest pikeperch size class. In larger size classes, the most selected prey were the large cladocerans. Water turbidity a¡ected the prey selection of the planktivorous pikeperch signi¢cantly. In more turbid environments, the larger zooplankters were more positively selected than the smaller ones. Turbidity decreased both total zooplankton consumption and Fulton's condition factor of ¢sh only in the largest size class of pikeperch. The e¡ect of turbidity on foraging and growth, and thus on the size of juvenile pikeperch of a particular year class is substantial under conditions where juveniles cannot shift from planktivory to piscivory.
Boreal Environment Research, 2008
The coastal reproduction areas of pike in the western Gulf of Finland were surveyed during spring 2004 and 2005 using a new approach. The locations of reed belts, the most important spawning substratum, were first identified using aerial photos, and 36 sites in three archipelago zones were selected for field sampling. The occurrence of pike larvae at each 100 m long site was observed with the aid of a white plate and a scoop. The majority of pike larvae were found in a habitat formed by the previous season's flattened reeds at a water depth of 20-80 cm. The comparison between archipelago zones revealed that reed belt shores in the innermost archipelago and bay area, substantially influenced by freshwater inputs in the spring, are the key reproduction areas of pike. Pike larvae were abundant in these areas, in contrast to the intermediate and outer archipelago, where pike larvae were found only sporadically. It is likely that productive habitats in the inner archipelago serve as a source and the outer archipelago as a sink, the latter maintaining pike population with the aid of juvenile immigrants from the main reproduction areas. The results also indicate that pike can not take full advantage of the slowly increasing spatial coverage of reed belts in the intermediate and outer archipelago of the western Gulf of Finland.
Turbidity decreases anti-predator behaviour in pike larvae, Esox lucius
Environmental Biology of Fishes, 2005
We tested how algal turbidity and light conditions influence anti-predator behaviour of first-feeding pike. Results showed that pike larvae were able to detect the predator by both chemical and visual signals in turbid water. However, the anti-predator behaviour was reduced in turbid water compared with clear water. Larvae hid in the vegetation in the presence of predator cues more in clear water than in turbid water. The attack rate on zooplankton in clear water was lower in the presence of predator cues, whereas no such difference was detected in turbid water. Both of these results indicate that turbidity acted as a refuge for larvae. Light proved to be an important regulating factor for feeding pike in the absence of predators, demonstrated as lowered attack rates in 50 light level in both clear and turbid water. This indicates that long-term turbidity may be critical for small larvae, which need to feed continuously to survive.