Shrimp Crangon Research Articles

Comparison of the nutritional transition date distributions of marbled sole larvae and juveniles in Hakodate Bay, Hokkaido

To examine survival processes in marbled sole Pseudopleuronectes yokohamae larvae, nutritional transition date distributions (NTDDs) were compared between larvae and large juveniles (LJs) in Hakodate Bay from 2001 to 2003. NTDDs were used instead of hatch date distributions because the onset of increment formation coincides with the timing of the transition from endogenous to exogenous nutritional sources for marbled sole. LJs were defined as being large enough to be safe from predation by the sand shrimp Crangon uritai. In 2001 and 2002, the ranges of the NTDDs of LJs largely overlapped with those of the larvae. However, in 2003, the early cohort (those whose otolith rings formed before 17 March) disappeared from the NTDDs during and after April, and the NTDDs of LJs were heavily biased toward a later period compared to those of the larvae. In 2003, Oyashio coastal water (<3°C and ≤33.0 salinity) unexpectedly intruded into the bay in late March and lowered the water temperature from 6.3°C on 6 March to 4.1°C on 25 March. One possible cause of mortality in the early cohort of 2003 may be feeding failure caused by the extremely low water temperature.

Spatial analysis of metal concentrations in the brown shrimp &lt;em&gt;Crangon crangon&lt;/em&gt; (Linnaeus, 1758) from the southern North Sea

Spatial distributions of Cu, Pb, Cd, Ni and Zn concentrations in brown shrimps Crangon crangon (Linnaeus, 1758) collected on a cruise of FRV Walther Herwig III to the southern North Sea in January 2004, were investigated on a scale of 18 x 18 km to evaluate the range of spatial autocorrelations for the different variables under study. Semivariogram models obtained by geostatistical procedures indicated a distinct increase in variability for most variables with sampling distance. Only if samples are taken at distances above the estimated values for the practical range of the semivariogram can stochastic independence of the data be assumed. These are 6.6 km for Cd, 3.0 km for Ni and 5.2 km for Pb. Contour plots revealed a clear coincidence of high values for Cd, Ni and Pb with low shrimp mean body wet weight. Nevertheless, spatial autocorrelations were rather weak, since classical and geostatistical population estimates for the means and the 95% confidence intervals were in good agreement. The low detected concentrations of Pb in C. crangon were in good agreement with reported data for decapod crustaceans from other regions. For Zn reported values were distinctly below our 95% confidence intervals, while for Cu they were slightly above and for Cd distinctly above concentrations in C. crangon from this study. For Ni no comparative values exist. We conclude that with this integrated biomonitoring approach metal concentrations could be assessed more precisely and relations between biotic and abiotic variables could be evaluated.

Quality of marinated shrimps: Influence of treatment, recipe and species characterised by physical measurements

The influence of processing treatments and additives on textural, water binding and colour attributes of marinated deep water pink shrimp (Parapenaeus longirostris) was determined. In addition, different shrimp types, brown shrimp (Crangon crangon) and deep water pink shrimp (PL) were compared regarding their textural, water binding and colour attributes after heat treatment to get an impression how different raw materials can influence the quality of the marinated end product. Texture measurement was performed as instrumental texture profile analysis using a texture analyser TA.XT2. Different texture parameters (hardness, chewiness, adhesiveness, cohesiveness and elasticity) were measured by double compression of the shrimps. Force of extrusion as well as Warner Bratzler shear force were also estimated. Water binding capacity was determined as expressible moisture and colour measurements were performed using a tristimulus ChromaMeter CR 300. Among the investigated variables, the marination time showed the highest influence on the textural parameters of marinated PL, whereas surprisingly almost no influence on texture parameters resulted from pre-treatment with sodium tripolyphosphate. A minor influence of all variables on the water binding capacity of marinated PL was observed, while colour values were affected moderately. Compared with refrigerated, vacuum-packed, cooked retail samples of brown shrimps (CC) differences in texture and colour were too obvious to allow a substitution of CC by PL due to completely different product characteristics.

Preliminary evaluation of effects of invasive tunicate management with acetic acid and calcium hydroxide on non-target marine organisms in Prince Edward Island, Canada

The proliferation of invasive tunicates in Prince Edward Island (PEI) estuaries has necessitated the development of approaches for managing tunicates that foul aquaculture structures, especially Styela clava and Ciona intestinalis. Spraying or immersion with a saturated solution of hydrated lime (calcium hydroxide) or 5% acetic acid are effective against these tunicates, but are also biocidal to a variety of non-target organisms as demonstrated by bioassays with the bacterium Vibrio fischeri, sand shrimp Crangon septemspinosa and threespine stickleback Gasterosteus aculeatus. Both chemicals have the potential to alter estuarine pH, which should remain within the limits 7.0-8.7 mandated by federal water quality guidelines. Acetic acid is no longer used as a commercial treatment in PEI and currently poses no risk to the environment. The pH of saturated hydrated lime solutions used for immersing mussel socks reached 12.6, but the “pH footprint” in the estuarine water column was limited to a radius of 5 tonnes/ha) of quicklime (calcium oxide) pellets mainly converted to hydrated lime within minutes, but chemical conversion of hydrated lime to harmless calcium carbonate took up to 18 days depending on temperature, pellet size, and the amount of quicklime applied. Conversion of hydrated lime to calcium carbonate should be more rapid at the much lower daily application rates (<0.007 tonnes/ha) of hydrated lime in powdered form, which represented the maximum amount likely to be used in mussel aquaculture for tunicate management in PEI. In most PEI estuaries, dilution by tidal mixing alone is probably sufficient to return the pH to normal values within a tidal cycle at these relatively low inputs of hydrated lime, even without taking into account the chemical conversion which would be occurring simultaneously. Decisions about whether to use chemical treatments must balance economic and potential environmental costs of treatment against the known economic consequences of unmanaged tunicate biofouling. A recent shift to use of pressure washing will reduce the potential for impacts associated with chemical treatments, but may not be feasible in estuaries infested with Styela clava.

Population zoogeography of brown shrimp Crangon crangon along its distributional range based on morphometric characters

Morphometry has been used in the investigation of the common shrimp Crangon crangon subpopulation structure at a local scale (100 km) around the UK. In the present study C. crangon populations were sampled over the whole distributional range from northern Norway to the Mediterranean and Black Sea to test whether the same method could be applied to describe subpopulation structure at a much larger scale (1000 km). Spatial variability in morphometric characters was determined by sampling 25 locations across the distributional range. In addition, the temporal variability in morphology was studied at 4 sites (Bodo, Norway; Wadden Sea, The Netherlands; Minho and Lima estuaries, Portugal). Contrary to expectations, temporal variability was observed in three of those sites resulting in an inability to distinguish between populations at the local scale. However, the large scale subdivision of shrimp populations from the Adriatic, Black Sea, Mediterranean and Atlantic were clearly identified. It is concluded that, while there are clear morphological differences between major zoogeographical zones, at a local scale, subpopulations frequently cannot be identified because of individual variability.

Relation between pH and enzyme expression in the midgut gland of the brown shrimp Crangon crangon

Relation between pH and enzyme expression in the midgut gland of the brown shrimp Crangon crangon

Sex-ratio, seasonality and long-term variation in maturation and spawning of the brown shrimp Crangon crangon (L.) in the German Bight (North Sea)

Aspects of the reproductive and maturation biology of the brown shrimp Crangon crangon (L.) were studied in various subareas of the German Bight (North Sea). The size-specific sex ratio of C. crangon was examined based on length frequency distribution data. The sex ratio for the smallest size groups at which sex was determined was typically around 0.5, indicating an even ratio between males and females. The proportion of females decreased in the 30–45 mm size range. In length classes larger than 50 mm, the proportion of females constantly increases to 100% at around 60 mm total length. We concluded that sex reversal from male to female may not occur in C. crangon. Size at sexual maturity was determined from the proportion of ovigerous females. Size at maturity (L50) was estimated as 55.4 and 62.0 mm total length for spring and winter data, respectively. The seasonal spawning cycle was studied over the period 1958–2005. Between mid February and late June and for size classes larger than 65 mm ovigerous shrimps exceeded 80% and reached up to 100% of the females in the population. This period can be seen as the core spawning season. From early August to early December the proportion of ovigerous shrimps in the female population is very low. Interannual differences in the seasonal process are obvious with a dramatic decline in C. crangon reproductive success in the late 1980s. Various options are discussed for the reasons of the decline and recovery of the reproductive performance.

The effect of ration size, temperature and body weight on specific dynamic action of the common cuttlefish Sepia officinalis

The effect of meal size (shrimp Crangon crangon) [0.83–18.82% dry body weight (Dw)] on specific dynamic action (SDA) was assessed in cuttlefish Sepia officinalis (1.03–6.25 g Dw) held at 15 and 20°C. Cuttlefish 2 g when given the same quantity of food. Handling, eating and digesting a shrimp meal was temperature dependent with cuttlefish processing and digesting a similar sized shrimp meal faster at 20°C than at 15°C. The proportional increase in oxygen consumption (2.07 ± 0.02) was not correlated with feeding rate (FR) and was independent of temperature and cuttlefish size. The SDA peak was not correlated with FRs, and increased as cuttlefish size and temperature increased. The mean SDA coefficient was 0.87 ± 0.07% of the ingested energy; one of the lowest SDA values recorded amongst vertebrates and invertebrates. Daily energy requirements (KJ day−1) for S. officinalis were calculated from laboratory estimates of energy losses due to standard (MO2 Standard), routine (MO2 Routine) and feeding (MO2 SDA) oxygen consumption. Laboratory estimates of daily metabolic expenditures were combined with results from previous investigations to construct an energy budget for 1 and 5 g cuttlefish consuming a meal of 5 and 15% Dw at 20°C and the amount of energy available for growth was estimated to be between 35 and 80.3% of the ingested energy.

Bioaccumulation of trace metals in the brown shrimp Crangon crangon (Linnaeus, 1758) from the German Wadden Sea

The objective of the present study is to evaluate the suitability of the brown shrimp Crangon crangon (Linnaeus, 1758) from the German Wadden Sea as a biomonitor for the trace metals Cd, Pb, Cu, and Zn and to analyse whether the two-compartment model sensu OECD could be used as a predictive tool to assess environmental quality. The tested decapods accumulated Cd and Pb upon exposure and it was possible to estimate significant model parameters of two-compartment models, while they did not respond to waterborn Cu and Zn. Kinetic BCFs at theoretical equilibrium were 860 for Cd and 750 for Pb. A tentative estimation showed the following sensitivity of C. crangon to an increase of soluble metal exposure: 0.4 μg Cd l −1 and 0.9 μg Pb l −1. Available information can be used to quantify a measure of agreement or disagreement between bioaccumulation in various decapods. This can be regarded as an important step in the calibration of biomonitors, which is necessary to assess the potential for bioaccumulation on different temporal and geographical scales.

Habitat selection of stone and starry flounders in an estuary in relation to feeding and survival

Juveniles of both stone flounder Platichthys bicoloratus and starry flounder Platichthys stellatus utilize estuaries as nursery grounds. To understand their habitat selection and the functions of habitats such as food supply, we defined the seasonal distribution of recently settled fish of these species in shallow nursery areas and investigated their feeding habits in the Natori River estuary, Japan. Distribution of stone flounder was limited to the lower estuary (<3 km upriver from the mouth) and stone flounder were most abundant near the mouth. Recently settled starry flounder were first detected further upstream in areas characterized by low salinity <10 and by the absence of the predatory sand shrimp Crangon uritai. Early juvenile stone and starry flounders consumed mainly siphons of the bivalve Nuttallia olivacea and the mysid Neomysis awatschensis, respectively; however, 1- and 2-yr-old fish of both stone and starry flounders fed mainly on the bivalve siphons. These results indicate that habitat selections of juvenile stone and starry flounders enable utilization of preferred prey and predator avoidance, respectively, and that non-overlap of these species' habitats results in avoidance of inter-specific competition for food between these two species.

Phylogeography of the common shrimp, Crangon crangon (L.) across its distribution range

The common or brown shrimp Crangon crangon (L.) is a highly abundant and important taxon, both ecologically and commercially, yet knowledge on its population structure and historical biogeography is limited. We studied population genetic structure across the distribution range of this species by sequencing a 388 bp fragment of the cytochrome- c-oxidase I gene for 140 individuals from 25 locations. Strong population structuring and high levels of genetic diversity were observed. Four main phylogroups were uncovered: northeastern Atlantic, western Mediterranean, Adriatic Sea and Black Sea. Gene flow of these shrimp across known oceanographical barriers (e.g., the Strait of Gibraltar and/or Oran-Almeria front, Sicilian Straits, and Turkish Straits) is severely restricted. The oldest and most variable populations currently inhabit the western Mediterranean. The observed absence of structure across the entire northeastern Atlantic shelf is proposed not to be due to gene flow, but to relatively recent colonization following the glacial cycles of the late Pleistocene. Black Sea shrimp are currently disconnected from Mediterranean populations, and colonization is inferred, on the basis of coalescent analysis, to have happened relatively recently, but possibly earlier than 7000 years ago. We postulate the hypothesis that C. crangon survived the last brackish-water (<7‰) period inside the Black Sea and/or one of the adjacent inland seas. We conclude that (1) common shrimp populations from different basins are strongly differentiated, (2) gene flow across basins is probably very limited, and (3) the biogeographic history of the taxon is largely in accordance with the geographic history of its distribution range. This study provides further evidence that high population connectivity of marine species (e.g., by policy makers) should not be assumed.

Effects of heavy metal contamination on the macrobenthic fauna in estuaries: The case of the Seine estuary

Heavy metal contamination levels are generally higher in estuaries than in the open sea. Some estuaries, the Seine estuary for example, have particularly high pollution levels of metals, yet continue to support a very high benthic biomass and remain quite productive. Measurements of sediment contamination are highly variable due to diverse chemical analysis methods, sediments origin and sources of contaminants found in the estuaries. Salinity appears to be the principal factor controlling contaminant distribution in the sediment and the overlying and/or interstitial waters; it also affects the bioavailability of contaminants in estuarine sediments. Of course, the response to contaminants varies greatly among species and assemblages. Trace metals explain only a small part of the variation in benthic community structure. Some species, such as the shrimp Crangon crangon, appears vulnerable to metal pollution, while other species, such as Scrobicularia plana, are able to tolerate quite high levels of cadmium in their tissue. This paper demonstrates the wide variability of benthic responses to contamination, which is probably due to the high spatio-temporal heterogeneity of the estuary. To reduce the problems due the heterogeneity and variability observed to date in the available results, it will be necessary to encourage integrated estuarine studies, in which sedimentologists, chemists, and biologists work together on the same campaigns at the same sites.

Inter-season and interannual variations in fish and macrocrustacean community structure on a eastern English Channel sandy beach: Influence of environmental factors

The intertidal zone of an exposed sandy beach on the French coast of the English Channel was sampled with a 1.5 m beam-trawl over five years (2000 and 2003–2006) at weekly intervals. The fish and macrocrustacean catches were analysed to determine the inter-season and interannual variation in community structure and relate these variations to changes in the major environmental variables. Only six species (plaice Pleuronectes platessa, common goby Pomatoschistus microps, sprat Sprattus sprattus, sand eel Ammodytes tobianus, brown shrimp Crangon crangon and shore crab Carcinus maenas) from the 27 species captured can be considered as dominant species of the intertidal zone, and they accounted for >90% of total numbers. Most individuals caught were young-of-the-year or juvenile. Analysis of similarities (ANOSIM) and similarities percentage (SIMPER) indicated that inter-season variability of community structure (mean average similarity = 47%) was more pronounced than interannual variability (mean average similarity = 65%). Canonical correspondence analysis (CCA) indicates that a substantial component (32.2%) of the measured inter-season variation in community structure can be explained by environmental factors (mainly water temperature). The main inter-season changes in the abundance and community structure were due to the variation of the six key species and reflect the different times of their recruitment. During the five years of the study, the structure of the fish and macrocrustacean spring community persisted from year to year, with the dominant species reappearing consistently even though their abundances fluctuated from year to year. This interannual variation probably reflects variable recruitment success influenced by physico-chemical conditions. In spite of the considerable interannual variation (40 times) in the spring bloom of the prymnesiophyte alga Phaeocystis globosa we found no effect of this bloom on either fish and macrocrustacean species densities or diversity index.

The ecological role of overwintering fish in the food web of the Culbin Sands lagoon ecosystem, NE Scotland: Identifying major trophic links and testing effects of the fish &lt;i&gt;Pomatoschistus microps&lt;/i&gt; (Pallas) on benthic invertebrates

The Culbin Sands lagoon ecosystem in NE Scotland was studied during a three-year period (1994-1996) to identify the major trophic links from benthic invertebrates to epibenthic predators, and to assess impacts of overwintering fish on their prey communities. Every 2-4 weeks, samples of mobile fauna were collected to study their diets. The major trophic links identified between benthic invertebrates and epibenthic predators were from benthic invertebrates to the shrimp Crangon crangon, and to the common goby Pomatoschistus microps and the plaice Pleuronectes platessa . The energy flow from benthic invertebrates to overwintering fish was estimated at 133 kJ m –2 yr –1 . A flow of 10 kJ m –2 yr –1 was also observed from eggs and larval stages of the overwintering shrimp Crangon crangon to the overwintering fish. Nevertheless, manipulative field experiments showed no significant impacts of the most abundant overwintering fish Pomatoschistus microps on prey community densities, despite an overall individual ingestion rate of 89 J day –1 .

Population dynamics, distribution and secondary production of the brown shrimp &lt;i&gt;Crangon crangon&lt;/i&gt; (L.) in a southern European estuary. Latitudinal variations

The population structure, growth, distribution and secondary production of the brown shrimp Crangon crangon (L. 1758) were examined between June 2003 and August 2005 at five stations in the Mondego Estuary, Portugal, using a 2-m beam trawl. Occurrence of immature shrimps suggested almost continuous reproduction with two main recruitment periods in November and March/April; this recruitment pattern is unique and represents a latitudinal transition in the species’ life cycle. Severe drought in winter 2004 caused spatial shifts along the north arm of the estuary regarding post-larval settlement in spring 2005. Mean growth of all cohorts was 0.06 mm TL day -1 , much lower than rates calculated elsewhere. Secondary production (P) of C. crangon was estimated at 4.6 mg AFDW m -2 y -1 (P/B– ratio of 8.7) in 2003/2004 and at 2.4 mg AFDW m -2 y -1 (P/B– ratio of 10.9) in 2004/2005. High abundances of individuals, predominantly juveniles, were observed in spring/summer with peaks in June 2003, April 2004 and July 2005. This study shows that this species dynamics must be analysed in a latitudinal context, meaning that the contribution of each component of the systems can vary according to environmental and climate variables.

Potential impact of temperature change on epibenthic predator–bivalve prey interactions in temperate estuaries

Temperate estuaries are indispensable as refuelling areas for long-distance shorebirds, where they depend on intertidal benthic fauna, such as bivalves, as food source. Bivalve recruitment is thought to be, at least partly, top-down regulated by epibenthic predators (the shrimp Crangon crangon and the crab Carcinus maenas) but this interaction is part of a complex predator–prey system since various fish species prey upon the crustaceans. The impact of climate change in temperate estuarine food web will be determined by how the various size-selective interactions are affected by temperature. This will depend on the temperature sensitivity of each species’ growth and on how food conditions allow them to fill in this growth potential. In this paper, the focus is on the first aspect: temperature sensitivity of the epibenthic predators compared with that of the bivalve prey and among the various predator species. Our results show that crustaceans have higher temperature sensitivity and tolerance range compared with their potential predators and with their bivalve prey. It is hypothesized that a temperature increase can potentially lead to an overall higher predation pressure in these systems with negative impacts in bivalve recruitment and hence, in the functioning of temperate estuaries as fuelling stations. However, prevailing food conditions for bivalves and predators will determine to what extent the potential impacts of an increase in temperature will be realized.

From flatfish to sticklebacks: assemblage structure of epibenthic fauna in relation to macroalgal blooms

On the Swedish west coast, blooms of green macroalgae have become a common feature over recent decades. Assemblage structure of epibenthic fauna was studied in randomly selected shallow soft substratum bays, with and without macroalgae, using quantitative sampling techniques. The study was performed biannually (June and August) over 4 yr in 4 regions along the coast. Mat-forming macroalgae on average covered 35% of the surface area in vegetated bays, with an overall mean biomass of 100 g DW m–2. The assemblage structure of epibenthic fauna was different in the presence of macroalgae, a pattern which was consistent over years and regions. Within the subset of bays containing vegetation, there were no bay-scale relationships between the biomass of algae and the abundance, biomass or number of species of epibenthic fauna. However, a detailed analysis revealed that the species had different responses to an increase in algal biomass at the scale of individual samples (0.5 m2). The flatfish Pleuronectes platessa occurred predominantly in samples completely free of vegetation. The shrimp Crangon crangon and the gobies Pomatoschistus spp. were found most commonly in the open sand habitat, and rapidly decreased in abundance with increasing biomass of algae. Gobius niger, Mysidacea, Anguilla anguilla, Sygnathus typhle and Palaemon spp. were most prevalent at a low to moderate biomass of algae. Sticklebacks (Pungitius pungitius and Gasterosteus aculeatus) increased in abundance with increasing algal biomass, and remained dominant at the highest level of algal biomass recorded. Thus, macroalgal blooms have the potential to change the structure and function of shallow soft substratum habitats, lowering their value as nursery and feeding grounds for commercial fish species.

Biology of the introduced copepod Pseudodiaptomus inopinus in a northeast Pacific estuary

Compared to other regions, estuaries and coastal bays along the west coast of North America have experienced the largest number of invasions by nonindigenous planktonic copepods. Eight species of copepods from Asia, including 2 species of the genus Pseudodiaptomus, have been reported in coastal bays of northern California, and a third species of Asian Pseudodiaptomus (P. inopinus) has become established in the Columbia River estuary and many smaller estuaries in the northeast Pacific Ocean. It can dominate the plankton in fresh and oligohaline tidal waters of estuar- ies that are utilized as rearing grounds for a variety of larger invertebrates and fishes. In July 1998 we initiated a 16 mo study of P. inopinus in the Chehalis River estuary, Washington State, USA, to docu- ment its biology, ecological relationships with other holoplankton, and importance as prey for fish and invertebrate planktivores. In 1998 P. inopinus reached peak densities in the late summer/early autumn period of low river flow but a similar peak was not seen in the same period in 1999, when densities of the copepod were significantly lower. These interannual density differences did not appear to be caused by between-year differences in predation or river flooding, but could have resulted from cooler temperatures and higher river flows that occurred in the Chehalis River in 1999. Other abundant planktonic copepods were separated from P. inopinus either temporally (Eurytemora affinis) or spatially (Acartia spp., Eurytemora americana) within the estuary, over a relatively short segment of the estuary spanning salinities of 0 to 10 psu. This separation may imply that P. inopinus experienced little competition when it was introduced; alternatively, it may have altered the distrib- ution of other copepods in the estuary. P. inopinus was rare in the diets of estuarine fishes, but com- prised an important and sometimes dominant prey for mysid shrimp Neomysis mercedis and juvenile caridean shrimp Crangon franciscorum. In turn, N. mercedis was an important prey item for estuar- ine fishes, and thus the main impact of P. inopinus on the estuarine food web was via this pathway.

A multispecies approach for monitoring persistent toxic substances in the Gulf of Gdańsk (Baltic sea)

Bivalve mussels are usually used for biomonitoring persistent toxic substances (PTS) in coastal ecosystems. Nevertheless, these organisms, which live attached on hard substrates, can be found along the sandy coasts only on human manufactured products. In this work different species collected in the Gulf of Gdańsk were compared to evaluate their suitability for monitoring PTS pollution at a local scale. The clam Mya arenaria seems to represent an excellent indicator of sediment pollution, mainly for organotin compounds which are selectively bioaccumulated. Organochlorine compounds are bioaccumulated in the different species mainly in function of their lipid body burden. Habitat conditions (salinity, substrate, pollution), however, strongly limited the occurrence of different species in the sampling sites; the most ubiquitous species, the common shrimp Crangon crangon, resulted therefore the most suitable to be used for the comparison of PTS pollution in this aquatic environment. Although the blue mussel ( Mytilus trossulus) was confirmed to be a very useful sentinel species to compare pollution level inside and outside the Gulf of Gdańsk, we recommend the use of other species to give a more detailed picture of the pollution situation in coastal areas.

Annual variation of potential predation impacts on larval and juvenile marbled sole Pseudopleuronectes yokohamae by sand shrimp Crangon uritai in Hakodate Bay, Hokkaido

An investigation was conducted to evaluate the annual variation in potential predation impact (PPI) on larval and juvenile Pseudopleuronectes yokohamae by Crangon uritai in Hakodate Bay using predator-prey size relationships. Laboratory experiments were designed to estimate the favorable prey size of C. uritai through back-calculation of body length (BL) of P. yokohamae from sagittal otolith diameter observed in the stomachs of C. uritai. The most favorable prey-predator size ratio (BL of P. yokohamae-total length (TL) of C. uritai) class was 0.15–0.19, and ranged from 0.12–0.31. There was a significant positive correlation between the BL increase of P. yokohamae and the bottom water temperature in the field, such that BLs stagnated during the cold year of 1999 from April to June, and increased during the warm year of 2002. In contrast, no significant correlation was found between the TL increase of C. uritai and the bottom water temperature. Moreover, there were no significant differences in the mean TL of C. uritai between months (April–June) or years (1998–2002). Variation of PPI depended on the relationships between the growth rates of P. yokohamae and bottom water temperature. Therefore, the warm year of 2002 resulted in higher potential predation impact (PPI≥20), and it was at least 20 days shorter than that of the cold year of 1999. These results suggest that increased bottom water temperature in the nursery area was one of the most important factors for cumulative predation loss.