Age determination and growth of juveniles of the European hake,Merluccius merluccius (L., 1758), in the northern Tyrrhenian Sea (NW Mediterranean)

The aim of the present study was to provide an estimation of growth of juvenile European hake, Merluccius merluccius (L., 1758) (OSTEICHTHYES; MERLUCCIIDAE), by means of the analysis of otolith daily increments. Hake specimens were collected during trawl surveys carried out in the northern Tyrrhenian Sea (NW Mediterranean). The sagittae were removed from hakes ≤20 cm total length. Left otoliths were ground and polished to obtain thin frontal sections. Otolith microstructure was analysed under a compound green light-polarising microscope. A power curve with intercept was fitted to the length-age data to describe the growth of M. merluccius. According to the growth curve, a mean length of 18 cm was reached at the end of the first year of life. The validation of the otolith increment periodicity was performed by means of two indirect methods.     

Otolith elemental characteristics of whitefish (Coregonus lavaretus) from brackish waters of the Gulf of Bothnia,Baltic Sea

To investigate whether European whitefish (Coregonus lavaretus) groups in the brackish (≤7%) Gulf of Bothnia (Baltic Sea) express specific otolith elemental characteristics, concentrations of elements (Ca, Ba, Sr, Zn, Mn, Fe) in whole otoliths were studied by inductively coupled plasma‐optical emission spectrometry. Whitefish (N = 67) were sampled from six different latitudinal sites; four in the sea and two in rivers along the west coast of Finland, and from a fresh water lake for comparison. The concentration of several elements showed significant differences among sampling sites. Otolith Ba concentrations were higher at the northern sampling sites compared to the southern ones, thereby showing negative association to capture‐habitat salinity. In contrast, otolith Sr and Zn concentrations were lower at the northern sampling sites, thereby associating positively to capture‐habitat salinity. Otolith Mn concentrations did not associate with latitude or salinity but markedly varied between sampling sites. Elevated Fe concentrations occurred in fish otoliths from the two northernmost sites. Ca concentrations were at the same levels in otoliths from all whitefish samples. Otoliths of whitefish from the lake had very high Ba and low Sr concentrations compared to concentrations in otoliths from whitefish in the sea and rivers. Our results show that otolith elemental characteristics of whitefish vary considerably at various geographic scales showing high potential for population identification using elemental fingerprints. Analysis of otolith elemental characteristics may therefore provide an efficient tool for the identification of main areas of residence, spawning locations, and migration routes, thus contributing towards the sustainable management of whitefish stocks.     

Multiple otolith techniques aid stock discrimination of a broadly distributed deepwater fishery species, blue grenadier, Macruronus novaezelandiae

This study investigated otolith shape, elemental chemistry of otolith cores (first 1-3 months of life), and stable isotope ratios (δ¹⁸O and δ¹³C) of whole otoliths as indicators of stock structure among three important southern Australian blue grenadier Macruronus novaezelandiae fishery regions; west Tasmania - WTAS, east Bass Strait - EBS, and Great Australian Bight - GAB. Comparisons were confined to two dominant cohorts of age 4+ and 13+ years, spawned in winter 2002 and 1993 respectively. Otolith shape varied significantly between the WTAS and GAB regions for the age 4+ cohort only. Cu:Ca of otolith cores was significantly higher for both cohorts from WTAS than EBS and GAB, and Ba:Ca of otolith cores higher for WTAS and EBS than the GAB region. Stable isotopic signatures showed greater variation among regions for the age 13+ cohort. In particular, otoliths of age 13+ fish from WTAS displayed significantly higher δ¹⁸O (indicative of lower temperature history) than age 4+ fish from all regions, and the same age fish from the GAB and EBS regions. δ¹⁸O of blue grenadier otoliths accurately predicted water temperature at their main capture depths of 400-600 m. Chemistry of otolith cores combined with whole otolith isotope ratios discriminated GAB and EBS samples from those collected on the known WTAS spawning ground with moderate to high (64-86%) accuracy. The results provide support for the hypotheses that the GAB fishery is based on a separate stock for management purposes, and that the EBS fishery is likely replenished both from local spawning and the major WTAS spawning region.     

Importance of estuarine nursery areas for the adult population of the temperate seabass Lateolabrax japonicus,as revealed by otolith Sr:Ca ratios

Otolith Sr:Ca ratios were used to evaluate the contribution of estuarine nursery areas to the temperate seabass (Lateolabrax japonicus) population in Tango Bay, the Sea of Japan. Otolith Sr:Ca ratios of juveniles collected from freshwater, brackish and coastal areas were analysed to determine a criterion for distinguishing whether individuals used estuarine or coastal areas as nurseries. Otolith Sr:Ca ratios of adult seabass collected around Tango Bay were also analysed to detect the records of salinity that juveniles experienced and to estimate the contribution of each habitat. Sr:Ca ratios of the edges of otoliths of juveniles from freshwater areas were 2.4 × 10^?3 in average, which were significantly lower than those of juveniles collected from a coastal area (4.9 × 10^?3 in average) owing to differences in salinity conditions among these areas. Based on the threshold criterion determined by this difference, 39 out of 107 (36%) adult seabass were estimated to have used the estuary as a nursery during their juvenile stage according to their Sr:Ca chronologies. Despite the small area covered by estuarine nurseries compared with coastal waters, the Yura River estuary contributed considerably to the adult seabass population. This indicates estuaries play an important role as nurseries for seabass juveniles, and it should be noted that the estuaries are important nurseries to conserve the stocks of coastal fishes.     

Spatial and temporal variation in otolith chemistry and its relationship with water chemistry: Stock discrimination of Sperata aor

Long‐whiskered catfish, Sperata aor (Hamilton 1822), is commercially important in food, ornamental and sport fisheries. The fish is mainly caught from the wild populations because its aquaculture practices are not commercialised. Inland fishery in the Ganga basin is mostly unorganised; hence, no published report is available on the trend of S. aor production from the selected habitat. In India, S. aor has been categorised vulnerable mainly due to natural and anthropogenic threats. Otolith chemistry shows variation with changing physico‐chemical conditions of the fish habitat. Therefore, the present study was conducted with the objective to analyse spatio‐temporal variations in water chemistry in relation to environmental factors; relationship between water and otolith chemistry; and spatio‐temporal variations in otolith chemistry to discriminate the stocks of S. aor inhabiting the River Ganga. Most of the element: Ca ratios in water samples did not show significant correlations with environmental factors, viz. temperature and conductivity. Only few element: Ca concentrations in otoliths were positively correlated to their corresponding ratios in the ambient water. In the selected study area, the S. aor populations were discriminated into four stocks possibly because of heterogeneous water chemistry at the sampling sites, and physical barriers. In the present study, otolith chemistry showed relatively low temporal variability as compared to spatial variability; thus, the classification accuracy of individuals to their original populations remained consistent over the selected time period. The findings could be useful in devising scientifically sound management strategies and/or any conservation plans for the vulnerable S. aor populations inhabiting the River Ganga.     

Otolith microstructure of chum salmon <Emphasis Type="Italic">Oncorhynchus keta</Emphasis>: formation of sea entry check and daily deposition of otolith increments in seawater conditions

To apply otolith microstructure to examination of age and growth of juvenile chum salmon Oncorhynchus keta inhabiting coastal waters, formation of otolith increments was investigated for juveniles reared in a seawater aquarium and in net pens. In all otoliths examined, a distinctive check was formed at the time of sea entry of the fish. The deposition of otolith increments after the check was daily for rearing both in the aquarium (57 days) and in the net pens (26 days). Check formation associated with sea entry was also observed in otoliths of juvenile salmon collected 1 km off the coast of Shari, Hokkaido, Japan. Transmitted light observation of otoliths of those fish revealed a transition in otolith increment appearance from dark to light. Otolith Sr: Ca ratio remarkably changed from a low to a high level, coinciding with the transition in otolith appearance. It is suggested that the transition was associated with individual sea entry. This study demonstrated that the check and/or transition associated with sea entry are applicable to a benchmark for otolith increment counts of juvenile chum salmon inhabiting coastal waters.     

Site fidelity and movements of an amphidromous goby revealed by otolith multi‐elemental signatures along a tropical watershed

Otolith microchemistry can provide crucial information to address gaps of knowledge in spatio‐temporal ecology of fish species. However, understanding the seasonal variability of water chemistry and its effect on otolith signatures is needed to interpret fish movements. Otolith multi‐elemental signatures were used to examine the diadromous migration and small‐scale movements of a tropical goby (Sicyopterus lagocephalus) within a watershed in La Réunion Island, Indian Ocean. The elemental ratios Sr:Ca, Ba:Ca and Sr:Ba recorded monthly in the water of nine sampling sites varied between localities and were correlated with otolith signatures, whereas the Mg:Ca signature was not. The incorporation of some trace elements in otoliths was influenced by the size of fish and site where they were caught, reflecting an effect of endogenous and exogenous factors. Despite these sources of variation, the elemental signatures did not overlap for three river sections distributed along the 26‐km‐long watershed. The diadromous migration and fish lifetime movements between these river sections were reconstructed using an original process based on random forest analysis. This approach revealed distinct migratory behaviours after fish entered in the river, with some individuals progressing slowly in the watershed whereas other rapidly reached the upper localities. As adults, S. lagocephalus showed a restricted exploratory behaviour and a strong site fidelity to a particular part of the watershed. The detection of adult movement was typically only between adjacent locations and is possibly explained by shifts in local intraspecific hierarchies and/or displacement during extreme discharge caused by cyclones.     

Natal origin and population connectivity of bigeye and yellowfin tuna in the Pacific Ocean

Natural chemical markers (stable isotopes and trace elements) in otoliths of bigeye tuna (Thunnus obesus) and yellowfin tuna (T. albacares) were used to investigate their origin and spatial histories in the western and central Pacific Ocean (WCPO). Otolith chemistry of young‐of‐the‐year (YOY) T. obesus and T. albacares from four regions in the WCPO was first determined and used to establish baseline chemical signatures for each region. Spatial variation in stable isotope ratios of YOY T. obesus and T. albacares was detected, with the most noticeable difference being depleted otolith δ¹⁸O values for both species from the far west equatorial and west equatorial regions relative to the central equatorial and Hawaii regions. Elemental ratios in otoliths were also quantified for YOY T. obesus and T. albacares collected in 2008, and several showed promise for distinguishing YOY T. obesus (Mg:Ca, Mn:Ca, and Ba:Ca) and T. albacares (Li:Ca and Sr:Ca). The natal origin of age‐1 to age‐2+ T. obesus and T. albacares was then determined for two regions of the WCPO, and mixed‐stock analysis indicated that T. obesus and T. albacares in our west equatorial sample were almost entirely from local production, with a minor contribution from central equatorial waters. Similarly, T. albacares collected in Hawaii were exclusively from local sources; however, a large fraction of T. obesus in Hawaii were classified to the central equatorial region, suggesting that the movement of migrants from outside production zones (i.e., south of Hawaii) are important to Hawaii's domestic fishery.     

Parallelism in thermal growth response in otoliths and scales of brown trout (Salmo trutta L.) from alpine lakes independent of genetic background

Low density in natural populations of salmonids has predominantly been managed by stocking of non‐native conspecifics. Due partly to domestication, introduced non‐native fish may be maladapted under natural conditions. Interbreeding between introduced and wild individuals may therefore impair local adaptation and potentially population viability. Brown trout (Salmo trutta L.) from three headwaters (with stocked fish) and three interconnected lakes (with native fish) on the Hardangervidda mountain plateau, southern Norway, were tested for differences in thermal effects on scale and otolith growth. Otolith and scale annuli widths from immature brown trout showed positive correlation with mean annual summer temperature for all six sampled populations. In mature individuals, a similar positive thermal correlation was evident for the otoliths only. Interannuli width measurements from scales indicate a halt in somatic growth for brown trout in this alpine environment when reaching ages between 7 and 9 winters, coinciding with age at maturity. Our study indicates that otolith growth follows summer temperature even when individuals do not respond with somatic growth in these populations and that introduced brown trout and introgressed populations have similar thermal growth responses. Due to the continued otolith growth after stagnation in somatic growth and the impact of fluctuations in summer temperature, the utilisation of otolith annuli widths for back calculation of length at age should be treated with caution.     

Transgenerational marking of brown trout Salmo trutta f.f., using an 84Sr spike

The maternal transmission of a naturally occurring and non‐toxic minor isotope of strontium (⁸⁴Sr) to the central otolith region of the progeny of a typical European freshwater fish species, brown trout, Salmo trutta f.f. L. was accomplished. The focus was to apply minimum doses of a non‐toxic solution at physiological salt concentration to minimise potential adverse effects on the fish. Female spawners were intraperitoneally injected with doses of 12.5 and 30.2 μg ⁸⁴Sr kg^?1 fish. Eggs were stripped and the resulting progeny were reared in a hatchery for about 1 year before sampling the otoliths. Strontium isotope ratios in the otoliths of the offspring were measured by cross‐sectional line scans using laser ablation‐multiple collector‐inductively coupled plasma mass spectrometry (LA‐MC‐ICPMS). Otolith cores of marked juveniles showed a significantly elevated ⁸⁴Sr/⁸⁶Sr ratio compared with control fish and to otolith regions created after hatching. Mass marking of cohorts of progeny from individually spiked brown trout with Sr isotopes is therefore possible for dispersal and migration studies without the necessity of handling eggs and applying other larval marking methods like immersion.     

Otolith biochronologies as multidecadal indicators of body size anomalies in yellowfin sole (Limanda aspera)

Dendrochronology (tree‐ring analysis) techniques have been increasingly applied to generate biochronologies from the otolith growth‐increment widths of marine and freshwater fish species. These time series strongly relate to instrumental climate records and are presumed to reflect interannual variability in mean fish condition or size. However, the relationship of these otolith chronologies to fish somatic growth has not been well described. Here, this issue was addressed using yellowfin sole (Limanda aspera) in the eastern Bering Sea, for which a 43‐yr otolith chronology was developed from 47 otoliths and compared with body size for 6943 individuals collected in 1987, 1994, and 1999 through 2006. Among several metrics of size normalized for age and sex, average body mass index (defined as weight/length) had the strongest relationship to the otolith chronology, especially when the chronology was averaged over the 5 yr preceding fish capture date (R² = 0.88; P < 0.001). Overall, sample‐wide anomalies in otolith growth reflected sample‐wide anomalies in body size. These findings suggest that otolith chronologies could be used as proxies of body size in data‐poor regions or to hind‐cast somatic growth patterns prior to the start of fisheries sampling programs.     

Otolith geochemistry in young‐of‐the‐year peacock bass Cichla temensis for investigating natal dispersal in the Rio Negro (Amazon – Brazil) river system

This study examined otolith geochemistry as a natural marker of natal origins in young‐of‐the‐year (YOY) Cichla temensis in the Negro River Basin of Brazil. We analysed trace element and isotopic composition of otoliths of YOY collected off spawning nests from the main stem and major tributaries. These were compared with regional bedrock geologic composition to explore underlying mechanisms of differences in otolith geochemistry. Our results suggest that spatial differences in otolith geochemistry can be used to distinguish natal origins based on ⁸⁷Sr/⁸⁶Sr, Sr/Ca and Ba/Ca ratios. This approach allowed us to correctly classify 99% of juvenile fish to their natal streams using cross‐validation in a linear discriminant function analysis (LDFA). Patterns of otolith isotopic composition correspond with patterns in regional geology as expected based on previously demonstrated correlations, although some fine‐scale spatial differences cannot be accounted for by available geologic information. These results demonstrate that otolith chemistry is valuable as a natural marker of natal origins in this system and suggest that inferences from geologic maps may be useful for interpreting movements based on otolith geochemical signatures. This information provides the basis for future work to investigate the early life history and spatial ecology of this important cichlid.     

Elemental fingerprinting in otoliths reveals natal homing of anadromous Baltic Sea pike (Esox lucius L.)

We examined the element pattern in the otoliths of a migratory fish species that inhabit the coastal areas in the brackish of the Baltic Sea. The northern pike (Esox lucius) show migratory behaviour, spawning in streams and rivers and foraging in the sea. We examined spawning migration in four nearby streams in the south‐west part of the Baltic. Otolith analysis by microPIXE revealed unique elemental patterns (Sr, Zn, Br, Co and Mn) for the juveniles in each of the different streams. The strontium signal in the otolith of the juveniles was used as an indicator of freshwater origin and the time spent in the stream. Adult pike in their migrating spawning phase were caught in each of the streams. The elemental composition in otoliths in their freshwater phase (using juvenile pike in the streams as references) was determined. A principal component analysis showed that the elemental fingerprint during the freshwater phase several years back in time was similar for the adult fish and for juveniles inhabiting the stream today. The results indicated natal homing of the adults to a specific stream, a conclusion that was strengthened by the fact that marked fish returned to spawn over consecutive years. Anadromous pike in the Baltic Sea may thus be divided in subpopulations. The results of the study may have implications for fishery management, as pike in the Baltic Sea cannot be seen as homogenous population.     

Otolith chemistry does not just reflect environmental conditions: A meta‐analytic evaluation

Fish otoliths are widely used to answer biological and ecological questions related to movements and habitat use based on their chemical composition. Two fundamental assumptions underlie otoliths as environmental tracers and proxies for reconstructing exposure histories: (i) otolith chemistry reflects water chemistry, and (ii) ambient environmental conditions affect otolith element incorporation. Here, we test these assumptions for Sr and Ba through meta‐analyses. Our first meta‐analysis confirmed a correlation between concentrations of Sr:Ca and Ba:Ca in otoliths and the surrounding water, both elements displaying positive otolith–water correlations. The second meta‐analysis examined the relative influences of salinity and temperature on otolith Sr and Ba partition coefficients (an index of otolith element regulation). Our environmental effects meta‐analysis confirmed that otolith Sr and Ba are affected by temperature and salinity; however, study‐level covariates (e.g., water chemical concentrations and species ecological niche) influenced otolith element incorporation, and this varied by element. These findings confirm that even though otolith chemistry and elemental incorporation are differentially affected by environmental conditions, other factors play a decisive role. While we focused on studies that directly linked water and otolith chemistry, systematic reviews are key to further demonstrate the link between otolith chemistry and extrinsic and intrinsic factors. Ultimately, disentangling the relative effects of multiple factors on otolith chemistry and a detailed understanding of biomineralization is critical to the continued use of otoliths as natural tags for tracing fish movements and habitat use.     

Discrimination of wild and hatchery trout by natural chronological patterns of elements and isotopes in otoliths using LA‐ICP‐MS

Abstract The potential to discriminate between wild and hatchery trout [Salmo trutta f. fario L. and Oncorhynchus mykiss (Walbaum)] by chronological microchemical patterns of different otolith regions was tested. Central and rim regions of otoliths were analysed for life stage specific elemental patterns of strontium (Sr), sodium (Na) and calcium (Ca) as well as of ⁸⁷Sr/⁸⁶Sr ratios using laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS). Classification to life stage specific habitats was achieved with 100% accuracy by ⁸⁸Sr/⁴³Ca, ²³Na/⁴³Ca and ⁸⁷Sr/⁸⁶Sr ratios resulting in a discrimination of hatchery fish from wild fish. ⁸⁷Sr/⁸⁶Sr ratios and Sr concentration in otoliths were positively correlated with the ratio and amount in the water. Na content in otoliths did not directly reflect the concentration in the water, although the ²³Na/⁴³Ca ratio in otoliths contributed to the discrimination. Clear differences in otolith chemistry were found for fish experiencing different geological units or a groundwater‐fed environment in a hatchery. Natural chronological microchemical patterns in otoliths proved to be a valuable tool for discriminating wild and hatchery fish without the necessity to use marking methods. LA‐ICP‐MS is well suited for this application because of its limited need for sample preparation, its potentially high sample throughput and the possibility of simultaneous measurement of multiple elemental and isotopic fingerprints.     

Are there life-history constraints on restoration of the endangered limpet Patella ferruginea (Mollusca,Gastropoda) in the northern Mediterranean Sea?

1. Effectiveness of restoration/repopulation measures may be strongly hindered by the ability of the target species to cope with the environmental conditions of the receiving area.
2. Although a species has been reported previously for a given area, the environmental conditions and human pressures may have changed, potentially making any restoration attempt ineffective. Evidence is provided showing that the endangered ferruginous limpet Patella ferruginea can complete its reproductive cycle in the northernmost sector of the western Mediterranean.
3. This supports the idea that the reintroduction and the strict protection of P. ferruginea in the extreme north of its historical geographic range could be effective for the recovery of the species in this area and ultimately the establishment of reproductively viable and stable populations.
4. Verification of gonadal maturation of specimens experimentally established on the Gulf of Genoa (Ligurian Sea) coastline, as well as evidence of sex change in one individual (the first outside the Alboran Sea), provides further support of the potential for individuals to complete their reproductive cycle in this area.
5. The results support the potential of actions for the restoration of viable populations of the species along the Ligurian coasts through the introduction of juveniles obtained exclusively by aquaculture techniques, in order to mitigate any impact on donor sites.

     

Linking growth to environmental histories in central Baltic young-of-the-year sprat, Sprattus sprattus: an approach based on otolith microstructure analysis and hydrodynamic modelling

Otolith microstructure analysis and hydrodynamic modelling were combined to study growth patterns in young‐of‐the‐year (YoY) sprat, Sprattus sprattus, which were sampled in October 2002 in the central Baltic Sea. The observed ‘window of survival’, approximated by the distribution of back‐calculated days of first feeding (DFF), was narrow compared to the extended spawning season of sprat in the Baltic Sea (mean± SD = 22 June ± 14.1 days) and indicated that only individuals born in summer survived until October 2002. Within the group of survivors, individuals born later in the season exhibited faster larval, but more rapidly decreasing juvenile growth rates than earlier born conspecifics. Back‐calculated larval growth rates of survivors (0.48–0.69 mm day^?1) were notably higher than those previously reported for average larval sprat populations, suggesting that the YoY population was predominantly comprised of individuals which grew faster during the larval stage. Daily mean temperatures, experienced across the entire YoY population, were derived from Lagrangian particle simulations and correlated with (1) detrended otolith growth and (2) back‐calculated, daily somatic growth rates of survivors. The results showed that abrupt changes in ambient temperature can be detected in the seasonal pattern of otolith growth, and that higher temperatures led to significantly faster growth throughout the entire age range of YoY sprat.     

Hydrogeomorphic factors drive differences in otolith morphology in fish from the Nu‐Salween River

Understanding the relationship between intraspecific phenotypic variation and habitat is fundamentally important to ecology and evolution. However, it is largely unknown whether the environment drives the morphological variation in riverine fish otoliths, which are potential phenotypic markers. In this study, we investigated morphological variations in the otoliths of an endemic Chinese fish (Schizothorax nukiangensis Tsao) collected from seven sites with varying environmental gradients along the Nu‐Salween River. We compared morphological characters of S. nukiangensis otoliths among sampling sites and identified environmental sources of otolith morphological variation using multivariate regression trees and multiple factor analysis. Results showed that S. nukiangensis otoliths collected from different habitats were significantly different in morphology, mainly at the rostrum, excisura and posterior rim. Variations in otolith morphology (specifically the increase in otolith length) were predominantly governed by average river gradient; this might be a functional response to hydrogeomorphic conditions. Other environmental gradients (i.e., altitude, latitude and average annual temperature) played a minor role in otolith shape. This study highlighted the role of environmental factors in determining the otolith shape in riverine fish; thus, species and population discriminations based on otolith morphology should consider intraspecific variability.     

Genetic connectivity supports recovery of gorgonian populations affected by climate change

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Climate‐induced environmental conditions influencing interannual variability of Mediterranean bluefin (Thunnus thynnus) larval growth

Daily growth variability of bluefin (Thunnus thynnus) larvae sampled in their Balearic Sea spawning grounds during the 2003–2005 spawning seasons was examined. Multi‐factorial ANOVA was applied to study the effects of environmental variables, such as temperature at 10 m depth (T10), microzooplankton dry weight (MDW) and protein/dry weight ratio (PROT/MDW) on larval growth. The 2003 bluefin tuna (BFT) larval cohort showed the fastest growth, recognizable from enhanced otolith and somatic mass increment compared to the 2004–2005 larval cohorts. The 2003 BFT larvae showed greater recent growth than the 2004–2005 BFT cohorts, which decreased in the last stages of development. Growth differences between the 2004 and 2005 larval cohorts were not significant. The environmental conditions between 2003 and 2004–2005 were highly contrasting as a result of the 2003 warming anomaly. Somatic and otolith growth rates (OGR) were significantly related to T10 and MDW, as well as to the PROT/MDW ratios. Nonetheless, the effect of T10 on OGR depended on the relative high (H) or low (L) levels of MDW and PROT/DW. Higher OGR was observed when T10 was high, MDW was low and PROT/DW was high. This environmental scenario conditions were met during 2003, which recorded the highest surface temperature and low planktonic biomass. Somatic growth, expressed as larval DW growth increase (DWGR), showed three‐factor significant interactions with T10*MDW*PROT/MDW, in which the two‐way interactions of MDW*PROT/MDW showed differences in the function of T10 levels.