Larval and juvenile development of dusky grouper Epinephelus marginatus reared in mesocosms

The larval development of the dusky grouper Epinephelus marginatus up to the benthic juvenile stage is described in detail to establish a reference for their larval identification. Development is described in terms of ontogenetic changes in morphology, growth, pigmentation, fin structure and skeletal structure. Larvae were reared in mesocosms at a mean temperature of 24·3° C, salinity of 36·5, dissolved oxygen of 6·4 mg l^?1 and pH of 8·2. Newly hatched larvae had an estimated total length (L_T) of 2·3 mm. On the second day post hatching the yolk was almost fully absorbed with traces of the oil globule still present, the eyes were already pigmented and mouth and gut functional. At this stage the cranial skeletal elements for feeding and breathing (mouth and gills) and the pectoral‐fin support were already present. About 50% of the observed larvae had food in their guts. Pigmentation was very characteristic, consisting of two large chromatophores visible on the edge of the primordial fin, close to the midpoint of the post‐anal region of the body and over the midgut and hindgut and post‐anal portion of the body. At 2·9 mm L_T the emergence of the second dorsal‐fin spine, characteristic of the Epinephilinae, was clearly visible. The pre‐flexion stage started in larva of 3·2 mm L_T. At 5·5 mm L_T the larvae possessed posterior preopercular angle spines, and the dorsal and pelvic spines presented serrated edges and were pigmented. The water surface‐tension‐related death of the yolk sac and pre‐flexion larvae described in the rearing of several other grouper species did not occur during E. marginatus culture. Notochord flexion, with initial ossification of the caudal‐fin supporting elements, started at 6·6 mm L_T. At this stage the major melanophores, preopercular, dorsal and pelvic spines and mandibular teeth were already present. Transformation of larvae into juveniles occurred when larvae averaged 13·8 mm L_T. Juveniles with a mean L_T of 20·1 mm started to settle and most of them were benthic with a mean L_T of 26·8 mm.     

The early life history of kurosoi,Sebastes schlegeli (Scorpaenidae), in the Sea of Japan

Larval and juvenile stages of kurosoi,Sebastes schlegeli, are described and illustrated from wild specimens. Some ecological aspects of larvae and juveniles are also described. Notochord flexion occurred between 5.6–7.5 mm SL. Transformation occurred between 13–20 mm SL. Preflexion and flexion larvae ofS. schlegeli can be distinguished from similar larvae by the pigmentation of the dorsal and ventral midlines of the tail and absence of pigmentation on the ventral portion of the rectum. After notochord flexion, the dorsal and lateral regions in both larvae and pelagic juveniles were heavily pigmented, suggesting adaptation for neustonic life style. Larvae and juveniles were caught at many coastal stations, but did not occur in cooler offshore waters. Larvae smaller than 20 mm SL inhabited surface waters. Until ca. 40 mm SL, juveniles inhabited mainly surface waters (without drifting seaweed), but also used other habitats, such as the drifting seaweed, and near the sea bed. Small larvae (<7 mm SL) fed mainly on copepod nauplii. Larger larvae fed on calanoid copepodites andEvadne nordmanni. Pelagic juveniles fed mainly on fish eggs, with fish larvae also being important food items for some individuals. Most food items taken by juveniles that were associated with drifting seaweed were eggs with attaching filaments (Cololabis saira andHyporhamphus sajori), suggesting that the high density of such food items both attracts and keeps juveniles around drifting seaweed.     

Growth and mortality of larval Myctophum affine (Myctophidae,Teleostei)

The growth and mortality rates of Myctophum affine larvae were analysed based on samples collected during the austral summer and winter of 2002 from south‐eastern Brazilian waters. The larvae ranged in size from 2·75 to 14·00 mm standard length (L_S). Daily increment counts from 82 sagittal otoliths showed that the age of M. affine ranged from 2 to 28 days. Three models were applied to estimate the growth rate: linear regression, exponential model and Laird–Gompertz model. The exponential model best fitted the data, and L₀ values from exponential and Laird–Gompertz models were close to the smallest larva reported in the literature (c. 2·5 mm L_S). The average growth rate (0·33 mm day^?1) was intermediate among lanternfishes. The mortality rate (12%) during the larval period was below average compared with other marine fish species but similar to some epipelagic fishes that occur in the area.     

Effects of Temperature and Body Size on the Swimming Speed of Larval and Juvenile Atlantic Cod (Gadus Morhua): Implications for Individual-based Modelling

Synopsis The routine swimming speed (S) of three groups of 4, 9 and 32 cm total length (L_T) juvenile cod (Gadus morhua) was quantified in the laboratory at 6 – 10 different temperatures (T) between 3.2 and 16.7°C. At temperatures between 5 and 15°C, mean group S increased exponentially with increasing T (S=a e^bT) and the effect of temperature (b = 0.082, Q₁₀ = 2.27) was not significantly different among the groups (over the 8-fold difference in fish sizes of early- and post-settlement juveniles). Differences in mean S among individuals within each group were quite large (coefficient of variation = 40 – 80%). Swimming data for juveniles and those collected for groups of 0.4, 0.7 and 0.9 cm standard length (L_S) larvae were combined to assess the effect of body size on S. At 8°C, S (mm s⁻¹) increased with L_S (mm) according to: S = 0.26L_S^Φ−5.28L_S⁻¹, where Φ = 1.55L_S^−0.08. Relative S (body lengths s⁻¹) was related to L_S by a dome-shaped relationship having a maximum value (0.49 body lengths s⁻¹) at 18.5 – 19 mm L_S corresponding to the sizes of fish at the end of larval-juvenile metamorphosis. Previous larval cod IBM’s using a cruise-predator mode likely overestimated rates of foraging (prey searching and encounters) by a factor of ~2, whereas foraging rates in pause-travel models are closer to estimates of swimming velocities obtained in this and other laboratory studies.     

Life history of an unusual marine fish: survival, growth and movement patterns of Hippocampus guttulatus Cuvier 1829

The life history of the long‐snouted seahorse Hippocampus guttulatus was characterized using mark‐recapture data collected within a focal study site and catch data from 53 additional sites in the Ria Formosa coastal lagoon, southern Portugal. Population structure in benthic habitats was characterized by high local densities (0·3–1·5 m^?2), equal sex ratios and few juveniles <70 mm. Adult H. guttulatus maintained small (19·9 ± 12·4 m²), strongly overlapping home ranges during multiple reproductive seasons. Recruited (benthic) juveniles exhibited significantly lower site fidelity than adults. A Ford‐Walford plot of standard length (L_S) at time t against L_S measured during the previous year from tagged juveniles and adults led to estimates of the von Bertalanffy parameters K = 0·571 and L_∞ = 197·6 mm. The growth rate of planktonic juveniles (inferred from previous studies), was greater than predicted by the von Bertalanffy model, providing evidence of an ontogenetic shift in growth trajectory. The instantaneous rate of natural mortality, M, ranged from 1·13 to 1·22 year^?1(annual survival rate = 29·4–32·2%). Sexes did not differ in movement, growth or survival patterns. On average, H. guttulatus measured 12·2 ± 0·8 mm at birth. Planktonic juveniles recruited to vegetated habitat at 96·0 ± 8·0 mm (0·25 years), had mature brood pouches (males only) at 109·4 mm (0·49 years), began maintaining home ranges and reproducing at 125–129 mm (0·85–0·94 years), and lived for 4·3–5·5 years. Early age at maturity, rapid growth rates, and short generation times suggested that H. guttulatus may recover rapidly when direct (e.g. exploitation) and indirect (e.g. by‐catch and habitat damage) effects of disturbance cease, but may be vulnerable to extended periods of poor recruitment.     

Physical changes in specimens of five species of Cyprinidae preserved in ethanol and frozen

Preservation in 30% ethanol and freezing to a temperature of ?20 ± 2° C is an appropriate method for measurement of fish eggs, larvae and juveniles. Egg diameter of the common carp Cyprinus carpio increased insignificantly by 1·32% after preservation compared with live size. The total length (L_T) of 1 day post‐hatching (dph) larvae as well as the standard length (LS) of 16 dph larvae of C. carpio increased significantly (2·95 and 1·50%, respectively) after preservation. Egg diameter as well as the L_T of 1 dph larvae of barbel Barbus barbus increased significantly after preservation, by 1·74 and 1·96%, respectively over their original size. The standard length (L_S) of 14 dph larvae of B. barbus as well as juveniles of B. barbus, crucian carp Carassius carassius, common nase Chondrostoma nasus and tench Tinca tinca decreased significantly after preservation (?0·56 to ?5·54%), whereas their body mass increased significantly (11·46–18·57%). Preserved eggs of C. carpio and B. barbus were hard, round and transparent. The larvae and juveniles of examined fishes, preserved in frozen ethanol, were straight, flexible and easily measurable after 60 days. Integrity of body surface and fins, as well as preservation of colours were much better in larvae or juveniles frozen and thawed only once than in specimens frozen and thawed thrice. Cooling in 30% ethanol to a temperature of 6 ± 2° C and freezing in water to a temperature of ?20 ± 2° C are not appropriate preservation methods for eggs and larvae of C. carpio (1 and 16 dph).     

Ontogenetic habitat shifts by Galaxias gracilis (Galaxiidae) between the littoral and limnetic zones of Lake Kanono, New Zealand

Synopsis Diel and spatial differences in distribution were determined for the larvae, juveniles, and adults of Galaxias gracilis (Galaxiidae) in a New Zealand dune lake during summer months. Larvae (mostly 10–25 mm TL) and juveniles (25–40 mm TL) inhabited shallow (0–3 m) waters of the limnetic zone and fed predominantly on two limnetic zooplankton species; Bosmina meridionalis and a calanoid copepod. At about 40 mm TL, fish moved from the limnetic to the littoral zone and expanded dietary breadth from two to over seven main prey species, including five species of littoral invertebrates. After reaching a size of about 60 mm TL, most fish moved back offshore to the deeper waters (5–15 m) of the limnetic zone during the day, moving back to the littoral zone at night to feed on invertebrates. The selection of different intra-lacustrine habitats by the various size groups of G. gracilis, and the movements between them, are interpreted as adaptive responses to the interaction between ontogenetic changes in feeding requirements and predation risk.     

Morphological characters and occurrence patterns of juveniles of two estuarine gobies,Acentrogobius kranjiensis and Acentrogobius malayanus,verified by molecular identification

Juveniles of two Acentrogobius species collected in a mangrove estuary in Sikao Creek, southern Thailand, were identified by morphological and molecular methods. A total of 1315 Acentrogobius specimens were collected and grouped into types A (n = 1107, 4·4–12·0 mm standard length, L_S) (melanophore absent or indistinct on posterodorsal contour of caudal peduncle; two rows of melanophore blotches on lateral midline) and B (n = 208, 4·8–12·6 mm L_S) (distinct melanophore on posterodorsal contour of caudal peduncle; a single row of melanophore blotches on lateral midline). Based on the reverse series method, the melanophore patterns of larger juveniles were linked with the smallest specimens possessing adult characters. The homogeneities of mitochondrial cytochrome b region sequences between the two juvenile types and adult Acentrogobius species collected in the study area indicated type A to be A. kranjiensis (homogeneity between type A and A. kranjiensis: 99·3–100%), and type B to be A. malayanus (homogeneity between latter 98·1 and 99·7%). No Acentrogobius juveniles were collected from the surf zone outside the creek mouth, both species apparently spending most of their life histories within the estuarine habitat. During their pelagic phase, A. kranjiensis and A. malayanus dispersed in the upper, middle and lower reaches of the creek. On the other hand, occurrence patterns during the benthic phase of A. kranjiensis and A. malayanus differed, the former showing upstream movement and the latter downstream movement with growth. These results emphasize the necessity of analysing early fish life histories at the species level, and the collaboration between morphological and molecular methods should prove valuable in accurately identifying of larvae and juveniles.     

Ontogenetic change in the amount and position of slow-oxidative myotomal muscle in relationship to regional endothermy in juvenile yellowfin tuna Thunnus albacares

Myotomal slow-oxidative muscle (SM) powers continuous swimming and generates heat needed to maintain elevated locomotor muscle temperatures (regional endothermy) in tunas. This study describes how the amount and distribution of myotomal SM increases with fish size and age in juvenile yellowfin tuna Thunnus albacares in relationship to the development of regional endothermy. In T. albacares juveniles 40–74 mm fork length (L_F; n = 23) raised from fertilised eggs at the Inter-American Tropical Tuna Commission Achotines Laboratory in Panama and larger juveniles (118–344 mm L_F; n = 5) collected by hook and line off of Oahu, Hawaii, USA, SM was identified by histochemical staining for the mitochondrial enzyme succinic dehydrogenase or by colour (in the two largest individuals). The cross-sectional area of myotomal SM at 60% L_F, a position with maximal percentage of SM in larger T. albacares, increased exponentially with L_F. The percentage of total cross-sectional area composed of SM at 60% L_F increased significantly with both L_F and age, suggesting that SM growth occurs throughout the size range of T. albacares juveniles studied. In addition, the percentage of SM at 60% L_F that is medial increased asymptotically with L_F. The increases in amount of SM and medial SM, along with the development of the counter-current heat-exchanger blood vessels that retain heat, allow larger tuna juveniles to maintain elevated and relatively stable SM temperatures, facilitating range expansion into cooler waters.     

Size and growth rate differences of larval Baltic sprat Sprattus sprattus collected with bongo and MIK nets

The effect of sampling with bongo (0·6 m diameter frame with 500 µm mesh) and Methot Isaac Kidd (MIK) (2 m diameter frame with 2 mm mesh finished with 500 µm codend) nets on standard length (L_S) range and growth rate differences was tested for larval Sprattus sprattus (n = 906, L_S range: 7·0–34·5 mm) collected during four cruises in the summer months of 2006, 2007, 2009 and 2010 in the southern Baltic Sea. Although the minimum size of larvae collected with the bongo and MIK nets was similar in each cruise (from c. 7 to 9 mm), the MIK nets permitted collecting larger specimens (up to c. 34 mm) than the bongo nets did (up to c. 27 mm). The growth rates of larvae collected with the bongo and MIK nets (specimens of the same size range were compared for three cruises) were not statistically different (mean = 0·55 mm day^?1, n = 788, L_S range: 7·0–27·4 mm), which means the material collected with these two nets can be combined and growth rate results between them were compared.     

High stocking density during larviculture and effect of size and diet on production of juvenile Lophiosilurus alexandri Steindachner, 1876 (Siluriformes: Pseudopimelodidae)

Different stocking densities were investigated in larviculture and feeding of Lophiosilurus alexandri, as well as analyses of the effects on juveniles of two size‐classes and two different commercial formulated diets. The first experiment was two‐phased: (a) larvae stocked at densities of 60, 120, 180, 240, and 300 larvae L⁻¹ fed with Artemia nauplii and reared for 15 days; (b) in phase 2, densities of 5, 10, 15, 30, and 40 juveniles L⁻¹ were evaluated during feed training (20 days). Mean water temperature in both phases was 28°C. In the first phase of experiment 1, the different stocking densities did not affect fish growth or survival. In phase 2, growth was similar in all densities; however, survival was lower at higher densities. The increased density provided a rise in biomass and number of individuals produced in both phases. In the second experiment, two size‐classes of feed‐trained juveniles (30.22 ± 1.84 and 34.66 ± 2.41 mm) were given pellets of two different diameters (1.2 and 2.6 mm) for 20 days. The largest juveniles fed the 1.2 mm inert diet had higher final weights and lengths. Larviculture and feed training of L. alexandri can thus be performed successfully at high stocking densities of 300 larvae L⁻¹ during the first 15 days of feeding, and at densities of up to 40 juveniles L⁻¹ during the 20 days of feed training, respectively.     

Spatial distribution and life‐history aspects of blackspot seabream Pagellus bogaraveo (Osteichthyes: Sparidae)

Spatial distribution and life history aspects of Pagellus bogaraveo in the eastern Ionian Sea were investigated using the data from 13 different studies carried out in the area from 1983 to 2010. The spatial patterns of the abundance, biomass and mean size showed that the species inhabits the shallow waters of the shelf (<170 m depth) as juveniles up to a certain size (<180 mm total length, L_T), moving to deeper waters of the slope (mainly 400–500 m depth) as adults. The spatial pattern of abundance indicated a continuous distribution of the species in deep waters, with hot‐spot areas of high values, whereas in shallow waters distribution was more discontinuous, with higher concentrations of juveniles in estuaries and brackish waters. The study of biological aspects of the species revealed (1) a difference in the increase in mass between males and females, (2) protandrous hermaphroditism, accompanied by the presence of primary females and males that do not change sex, (3) a sex ratio in favour of females >250 mm L_T, (4) the presence of hermaphrodites between 200 and 370 mm, (5) a long reproduction period from June to March, (6) a size at first maturity around 300 mm and (7) a diet composition of adults based mainly on fishes, and also on opportunistic behaviour in the food scarce environment of deep waters. The results suggest that the species' distribution and feeding strategies are the most appropriate for the oligotrophic eastern Ionian waters and that these conditions result in smaller sizes of the species in the east Mediterranean Sea compared to the west basin and the east Atlantic Ocean, with implications for the growth and reproductive biology of the species.     

Ontogenetic diet shift of age‐0 year Pacific bluefin tuna Thunnus orientalis

Stomach contents of 437 age‐0 year Pacific bluefin tuna Thunnus orientalis (20·3–59·4 cm fork length, L_F) caught in the Tsushima Current and the Kuroshio regions around Japan were examined to investigate their ontogenetic diet shift. Prey compositions were diverse and different between regions. Although the seasonal growth patterns were different between regions, ontogenetic diet shifts shared a common pattern. In the Tsushima Current region (Sea of Japan), small T. orientalis (20–25 cm L_F) preyed upon small squid (juvenile Enoploteuthis chunii), and larger ones (25–35 cm L_F) gradually shifted their diet to mesopelagic fish (Maurolicus japonicus). In the Kuroshio region (Pacific Ocean), small T. orientalis (20–25 cm L_F) preyed upon small zooplankton (mostly crustacean larvae), and larger ones (25–40 cm L_F) shifted to epipelagic fishes (Etrumeus teres, Sardinops melanostictus and Engraulis japonicus). The observed data suggest that T. orientalis switch to a diet more based on fish prey items, which have more body mass and greater swimming ability than small squid and zooplankton, after they reach a L_F of 25 cm.     

Parasitic copepods affect morphospace and diet of larvae of a temperate reef fish

The effects of ectoparasites on larvae of the clingfish Gobiesox marmoratus were evaluated at the dietary and morphometric levels. The larvae and ectoparasites were collected by nearshore plankton samplings during October, November and December 2013 off El Quisco Bay, central Chile. The standardized abundance of total larvae and those ectoparasitized larvae (PL) was positively related and high parasite prevalence was found throughout the sampling period (up to 38%). Geometric morphometrics analyses indicate main changes in the shape through early ontogeny and subtle but significant variations between PL and non‐parasitized larvae (NPL). Prey composition varied between PL and NPL; small size (<6 mm standard length, L_S) parasitized larval G. marmoratus ate mostly gastropod larvae, whereas small non‐parasitized specimens ate mainly cirripede nauplii. All larger (>8 mm L_S), pre‐settlement stages parasitized by Trifur and, or Caligus copepods had content in their gut, suggesting that ectoparasites did not diminish prey capture in host with larger size. Morphometric and dietary changes occurring during larval development were decoupled, both for PL and NPL. The maintenance of a slender, more hydrodynamic body through pelagic development and the ingestion of less‐mobile prey in PL suggests non‐lethal effects of ectoparasitism on rocky‐reef fish larvae.     

Non-target effects of kaolin and coppers applied on olive trees for the predatory lacewing Chrysoperla carnea

Kaolin clays and copper salts might be considered as alternative chemical control products for controlling olive pests in the contexts of both organic farming and integrated pest management programmes. Chrysoperla carnea (Stephens) (Neur. Chrysopidae) represents one of the most significant generalist predators of olive grove pests. In this study, we evaluated the side effects of these compounds on the predatory lacewing. First, kaolin and two copper salts (copper oxychloride and Bordeaux mixture) were tested on C. carnea eggs to determine their effects on egg viability and larval hatching suppression by topical application. Second, L₃ larvae were exposed to the pesticide residues on treated olive tree leaves. Third, a series of three residual tests in adults were sequentially performed as follows: residues on glass surfaces, on olive tree leaves and on small olive trees. Finally, kaolin- and water-treated eggs of Ephestia kuehniella Zeller (Lep. Pyralidae) were offered to L₃ larvae in both dual- and no-choice tests. C. carnea egg hatching was reduced by the kaolin treatment compared to the control treatment. Residual treatments were harmless to larvae and adults, without any deleterious effects on reproduction. L₃ larvae consistently preferred to feed on water-treated E. kuehniella eggs compared to kaolin-treated eggs. The larvae from the no-choice test that had fed ad libitum until pupation on kaolin-treated E. kuehniella eggs, pupated and emerged as healthy adults in reduced proportions compared with those that fed on water-treated eggs. In conclusion, our data suggest that both kaolin and copper products appeared to be largely harmless or only slightly harmful to the predator.     

Occurrence of Gobiidae larvae in a tropical Brazilian estuary,with particular emphasis on the use of size classes to categorize species guilds

The structure and seasonal dynamics of larvae of the Gobiidae family in the Mucuri Estuary (Bahia, Brazil) were studied for nine consecutive years. Sampling was conducted at three stations in the lower estuary channel, between 2002 and 2010, in relation to season, day and night and tidal variations. A total of 5802 Gobiidae larvae, representing 15 taxa (12 species and three morphotypes), were collected in the Mucuri Estuary during this time. The highest mean ± s.d. density of fish larvae, 54·7 ± 79·8 larvae 100 m^?3, was recorded during the flood tide and night sampling. Ctenogobius boleosoma was the most abundant species (68%), being dominant in the rainy and dry seasons and had a long reproductive period. This species was classed as a marine estuarine‐opportunist because it was observed at high frequencies and active larvae entering the estuary between 6·1 and 12·0 mm standard length (L_S). Gobionellus oceanicus, second in abundance (12%), occurred only in later larval stages but did not use the estuary as a preferred location for spawning, being classed a marine estuarine dependent. Microgobius carri (11%) was represented in all L_S classes and was resident in the estuary for spawning, remaining there throughout their life cycle. The other species were considered rare due to their low densities and could not be classified in any guild.     

Distribution and species composition of juvenile and adult scombropids (Teleostei,Scombropidae) in Japanese coastal waters

Two scombropid fishes, Scombrops boops and Scombrops gilberti, are closely related and commercially important species in Japan. These species are often confused in commercial markets because of their morphological similarity. In this study, scombropid specimens collected from various Japanese coastal waters were subjected to polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis and phylogenetic analysis of the 16S rRNA gene in mitochondrial DNA. These analyses showed that all the scombropid specimens collected from localities in the Sea of Japan were identified as S. boops, whereas those from the Pacific Ocean included two species, S. boops and S. gilberti. Almost all juvenile (<200 mm standard body length, S_L) S. gilberti originated from the Pacific coastal waters of the northern Japan, whereas adults (>400 mm S_L) were found only in deep water off the Izu Peninsula to the Izu Islands. This suggests that S. gilberti might migrate extensively during its life cycle. In addition, differences in the number of specimens and the distribution between the two species suggest that S. gilberti is less abundant than S. boops in Japanese waters.     

Feeding ecology of juvenile turbot Scophthalmus maximus and flounder Pleuronectes flesus at Gotland, Central Baltic Sea

Food and feeding of juvenile turbot Scophthalmus maximus and flounder Pleuronectes flesus were studied in five nursery areas at Gotland, Central Baltic Sea, ICES SD 27 and SD 28. Ontogeny involved partitioning of available food resources. The food choice of turbot <30 mm standard length (L_S) included both planktonic‐hyperbenthic prey (calanoid copepods and mysids) and epibenthic–endobenthic prey (chironomids and amphipods), whereas turbot ≥30 mm L_S fed mainly on hyperbenthic species (mysids and fishes). Conversely, for flounder, epibenthic–endobenthic prey were the most abundant prey items throughout development (harpactocoid copepods, oligochaetes and chironomids for fish <40 mm L_S and oligochaetes, chironomids and amphipods for flounder ≥40 mm L_S). Thus, the highest degree of dietary overlap occurred between turbot <30 mm and flounder ≥40 mm. Food composition for both turbot and flounder varied, however, according to exposure and predominant wind direction in the nursery area. For example, expressed as the ratio between the biomass of mysids and fishes consumed, the relative importance of mysids v. fishes as food source for turbot, varied from <1 in the most sheltered area to 16 and 27 in the more open areas. Considerable differences in feeding incidence were recorded; mean ±s .d . 58 ± 20% for turbot <30 mm L_S and 83 ± 8% for turbot ≥30 mm L_S, as opposed to ≥85–90% for flounder irrespective of size. The lower feeding success of turbot <30 mm L_S was related to mysid abundance, shown to vary spatially and temporally, and to density of flounder, indicating that food availability, and potentially interspecific competition, influence feeding of early juvenile turbot with implications for survival following settlement. Regarding variability in abundance, hyperbenthic prey, as mysids, are considered more variable than epi‐ and endobenthic organisms. Hence, in addition to the ‘nursery size hypothesis’, i.e. the positive relationship between abundance of recruits and extension of nursery areas, variability in food availability may explain the average lower recruitment of turbot as compared to other flatfishes, e.g. flounder.