Yellowfin Sole Limanda Aspera Research Articles

THIN AND ULTRATHIN STRUCTURE OF ENVELOPES OF STEPHANOSTOMUM BACCATUM (TREMATODA: ACANTHOCOLPIDAE) METACERCARIAE IN YELLOWFIN SOLE, LIMANDA ASPERA.

The structure of the envelopes (capsule and cyst) surrounding metacercariae of Stephanostomum baccatum (Nicoll, 1907) in the second intermediate host, the yellowfin sole Limanda aspera (Pallas 1814), is examined with the methods of light and transmission electron microscopy. The cyst, presumably formed by secretions of the metacercarial tegument, consists of 2 layers: the outer, very thin layer of an electron-dense, finely granular substance and the inner layer composed of loose material of a moderate electron density that includes dense bodies varying in size, shape, and localization. The capsule, formed by the host's cells, is also organized into 2 distinct layers. The inner layer of the capsule is loose, consisting of evenly spaced debris of degenerated cells and lipid droplets with inclusions of intact macrophages between them. The outer layer of the capsule consists of parallel rows of cells arranged around the parasite, with fibroblasts and macrophages being dominant types and granulocytes and lymphocytes found in smaller numbers. Aggregations of collagen fibers are located in narrow spaces between the cells. The number of lipid droplets in the outer layer is significantly smaller than in the inner layer. The capsules formed around the examined trematodes have several structural features that distinguish them from those of S. baccatum and Stephanostomum sp. metacercariae recovered from other fishes of the family Pleuronectidae. The major morphological features of such capsules are the lack of epithelioid or giant multinucleated cells and the presence of numerous lipid droplets. Investigating the structural details of the envelopes surrounding metacercariae in trematodes, as well as other helminths, contributes to our scientific understanding of parasite biology, which can, in turn, have broader implications for understanding host-parasite interactions and evolutionary biology.

Distribution and Ecology of Yellowfin Sole Limanda aspera and Sakhalin Sole L. sakhalinensis (Pleuronectidae) in the Pacific Waters of Kamchatka in Summer 2016–2020

Distribution and Ecology of Yellowfin Sole Limanda aspera and Sakhalin Sole L. sakhalinensis (Pleuronectidae) in the Pacific Waters of Kamchatka in Summer 2016–2020

On the intraspecific competition of yellowfin sole Limanda aspera (Pallas, [1814]) (Pleuronectidae) in the eastern part of the Sea of Okhotsk

Based on the longterm observations for 1963–2019, the article provides an assessment of the yellowfin sole generation mortality dynamics depending initial abundance and population dynamics in view of abundance and biomass. Individual growth and matiration rates were evaluated in generations with different initial abundance and in different states of population dynamics. Results indicated about intraspecific competition in yellowfin sole in the eastern part of the Sea of Okhotsk, expressed in specifics of the dynamics of stock abundance, growth and maturation. Forming generation stock abundance in early and later ages has different character. The more exceeding number of parental eggs spawned, the more generation abundance of yearlings getting exactly compensated by mortality (complete compensation). Older generations demonstrate the phenomen of “overcompensation”, when mortality of generations appeared in the years of higher egg production exceeds fertility. In the period of population growth and stabilization at a high level the period of the Yellowfin sole abundance fluctuation cycle gets shorter and the amplitude – smaller. Effects of intraspecific competition on the growth of individuals are revealed. Negative effects of the competition authentically revealed in elder age groups were not observed in younger age groups. An increase of the Yellowfin sole abundance brings negative effects on maturation rate of males with almost no such effects on females. To the greatest extent such effects can be seen in young age groups, at the beginning and middle stage of maturation.

ПОЛОВОЕ СОЗРЕВАНИЕ ДВУХ ВИДОВ КАМБАЛ (PLEURONECTES QUADRITUBERCULATUS И LIMANDA ASPERA) (PLEURONECTIDAE) У БЕРЕГОВ ЮГО-ВОСТОЧНОЙ КАМЧАТКИ

The paper presents the characteristics of sexual maturation of the yellowfin sole Limanda aspera and the lemon sole Pleuronectes quadrituberculatus off the coast of southeastern Kamchatka in 1959–2020. The proportion of mature fish depending on the length was analyzed on the basis of empirical and theoretical data, the dynamics of maturation of the gonads of males and females of two flounders by months was characterized. In the Pacific waters of Kamchatka, males and females of the yellowfin sole mature at a smaller size than in the eastern part of the Bering Sea and at a larger size than off the coast of Western Kamchatka. Mass maturation of lemon sole takes place first in the eastern part of the Bering Sea, then near southeastern Kamchatka, and lastly on the western Kamchatka shelf.

Variation in the distribution of yellowfin sole Limanda aspera larvae in warm and cold years in the eastern Bering Sea

AbstractMultiyear periods of relatively cold temperatures (2007–2013) and warm temperatures (2001–2005 and 2014–2018) altered the eastern Bering Sea ecosystem, affecting ocean currents and wind patterns, plankton community, and spatial distribution of fishes. Yellowfin sole Limanda aspera larvae were collected from the inner domain (≤50 m depth) of the eastern Bering Sea among four warm years (2002, 2004, 2005, 2016), an average year (2006), and three cold years (2007, 2010, 2012). Spatial distribution and density of larvae among those years was analyzed using generalized additive models that included timing of sea‐ice retreat, areal coverage of water ≤0°C, and water temperature as covariates. Analyses indicated a combination of temperature effects on the location and timing of spawning, and on egg and larval survival, may explain the variation in larval density and distribution among years. During warm years, higher density and wider spatial distribution of larvae may be due to earlier spawning, an expansion of the spawning area, and higher egg and larvae survival due to favorable temperatures. Larval distribution contracted shoreward, and density was lower during cold conditions and was likely due to fish spawning closer to shore to remain in preferred temperatures, later spawning, and increased mortality. Predicted drift trajectories from spawning areas showed that larvae would reach nursery grounds in most years. Years when the drift period was longer than the pelagic phase of the larvae occurred during both warm and cold conditions indicating that settlement outside of nursery areas could happen during either temperature condition.

Greater exposure of nearshore habitats in the Bering Sea makes fish early life stages vulnerable to climate change

Marine fish species with complex life cycles undergo ontogenetic changes in their physiological and habitat requirements. Therefore, predicting how warming ocean conditions are likely to impact fish populations requires size-(age-) and habitat-specific analyses. We determined the habitat exposure and scope of adaptability of 4 shelf-oriented flatfish species in the Bering Sea to projected climate-driven warming. We quantified present day and end-of-century habitat exposure based on hindcasts and forecasts of regional ocean circulation models and quantified fish adaptability based on changes in depth distribution and from published thermal tolerances of northern rock sole Lepidopsetta polyxystra, yellowfin sole Limanda aspera, Alaska plaice Pleuronectes quadrituberculatus, and flathead sole Hippoglossoides elassodon. These 4 species complete their life cycle within the Bering Sea shelf but have different depth preferences and thermal tolerances throughout ontogeny. We found that species or size ranges that occupy the inner shelf, such as northern rock sole, yellowfin sole, and Alaska plaice, are exposed to higher seasonal variability compared to outer shelf species. While these inner shelf species are likely adapted to large seasonal changes in temperature, the future range of seasonal variability was projected to exceed their thermal tolerances. Therefore, we expect species that reside inshore during part of their life cycle and have high temperature sensitivity and limited mobility to be particularly vulnerable to climate change.

Availability of yellowfin sole Limanda aspera to the eastern Bering Sea trawl survey and its effect on estimates of survey biomass

Availability of yellowfin sole Limanda aspera to the National Marine Fisheries Service eastern Bering Sea trawl survey, rather than trawl sampling efficiency, is proposed as the primary reason for relatively high annual variability of biomass estimates in this region, including most recently, a 48% increase from 2015 to 2016. The main hypothesis presented here is that temperature-mediated differences in the timing of spring-summer spawning migrations to unavailable nearshore spawning grounds, affect survey biomass estimates. Colder bottom temperatures delay both migrations and spawning, causing higher proportions of mature individuals to reside in the unavailable nearshore grounds at the time of annual survey (June–July). Indicators of this scenario include decreases of mature fish proportions and decreases in mean overall fish lengths during colder years when biomass was less than expected. Further evidence includes differences in spatial distribution between warm and cold years, and spatial shifts away from nearshore areas between early June and July–August sampling during which catch per unit effort (CPUE) increased and proportion of females increased. That neither of these spatial shifts nor temperature-CPUE relationships occurred for northern rock sole Lepidopsetta polyxystra, a species of similar morphology and abundance, and overlapping spatial distribution, suggests that temperature-mediated trawl sampling efficiency was not a major contributing factor for yellowfin sole. We have also found a positive relationship between survey biomass estimates and survey start times, reinforcing that availability is a function of timing. The addition of survey start time to the catchability (q) parameter within the current stock assessment model significantly improved model fits to abundance data.

Practice of assessing the resources of fish in Peter the Great Bay by data of Danish seine catches

Marine biological resources are usually assessed by trawl surveys; methods of these surveys are well-developed. However, number of fish populations is too high to be completely assessed by scientific surveys, so the data of commercial fishery have to be used, too. Danish seine is preferable method of the Russian commercial fishery in the Japan Sea and some other areas of the Russian EEZ. Principal possibility of fish stocks accounting with Danish seine is tested earlier by specialists of Kamchatka Research Institute of Fisheries and Oceanography for the West Kamchatka where the parallel surveys by trawl and Danish seine were compared that showed similar results. Continuing these experiments, the data of Danish seine catches in Peter the Great Bay are compared with the data of trawl catches in the same area. In spite of differences in construction of the Danish seine and trawl, the fish resources assessments by these gears are similar in this area, too. Some differences are associated with the three times thicker layer caught by the Danish seine. Because of this reason, yellowfin sole Limanda aspera prevailed in the catches of Danish seine but other Pleuronectidae plaices were more numerous in the trawl catches, obviously because of their aggregation closer to the bottom.

LONG-TERM AVERAGE BIOMASS AND DOMINANT FISH SPECIES IN THE BOTTOM BIOTOPES OF THE OKHOTSK SEA. PART 1. COMPOSITION AND QUANTITATIVE RATIO OF SPECIES ON SHELVES IN DIFFERENT AREAS OF THE SEA

Composition of the demersal fish community in the bottom biotopes of 14 biostatistical areas of the Okhotsk Sea is considered on the data of 9,189 standard trawl catches obtained in 95 expeditions conducted by Pacific Fish. Res. Center (TINRO) in 1977–2010. The most abundant fish species in each area are ranked by biomass. The total demersal fish biomass is estimated as 9583.0 . 103 t (2124.9 . 103 t without pollock and herring). The most numerous demersal species are: pacific cod Gadus macrocephalus, yellowfin sole Limanda aspera, pacific sand lance Ammodytes hexapterus, great sculpin Mycocephalus polyacanthocephalus, and saffron cod Eleginus gracilis.

Species composition and biomass of fishes by the data of bottom trawls in the northwestern Japan Sea in 1978-1990

State of the demersal fish community in the northwestern Japan Sea in the period 1978-1990 is considered on the data of bottom trawl surveys. Mean total biomass of the demersal fish in the USSR economic zone in those times is estimated as 1.106 . 10 6 t. The bulk of fish community was formed by the families Gadidae, Pleuronectidae, Clupeidae, Hexagrammidae, and Cottidae with summary portion 95.1 % by biomass and 84.8 % by number. The most abundant fish species were walleye pollock Theragra chalcogramma (44.8 % of the biomass), scale-eye plaice Acanthopsetta nadeshnyi (12.2 %), pacific herring Clupea pallasii (8.6 %), blackfin flounder Glyptocephalus stelleri (7.7 %), pacific cod Gadus macrocephalus (4.7 %), and arabesque greenling Pleurogrammus azonus (4.6 %), portions of other species didn’t exceed 3 %. The summary portion of flounders (23 species) was 28.0 %, by biomass. Scale-eye plaice dominated among them (on average 135.4 . 10 3 t), other mass flounders were the blackfin flounder (84.8 . 10 3 t), yellowstriped flounder Pseudopleuronectes herzensteini (29.0 . 10 3 t), and yellowfin sole Limanda aspera (13.2 . 10 3 t) though the latter species had dominated there in the 1930s.

Biological features of common fish species in Olyutorsky-Navarin region and the adjacent areas of the Bering Sea: 3. Righteye flounders (Pleuronectidae)

Biological features of the seven abundant commercial species—the Pacific halibut Hippoglossus stenolepis, the Greenland halibut Reinhardtius hippoglossoides, the Alaska plaice Pleuronectes quadrituberculatus, the northern rock sole Lepidopsetta polyxystra, the yellowfin sole Limanda aspera, the flathead sole Hippoglossoides elassodon, and the Bering flounder H. robustus (Pleuronectidae)—have been studied for a 20-year period (1995−2015). These species are present in the northwestern Bering Sea in the summer–autumn season; they form the gatherings in Olyutorsky-Navarin region. The size-weight spectra of the fish caught by different fishing gear has been analyzed, the peculiarities of the linear growth and the weight gain, as well as the spawning period and scale and the spawning conditions, have been described. The largest halibut specimens have been registered in the bottom setlines and gill nets, while flounders were in snurrevad catches; the smallest specimens have been observed in trawl catches. The abundant year-class in most of the studied species is seen well on the long-term plots of the fish size spectra and is tracked by the decrease of their biological parameters. The species that demand vast growing grounds (Pacific halibut, Alaska plaice, northern rock sole, and yellowfin sole) are characterized by a smaller average body size of the fish sampled in the coastal waters due to the prevalence of the young specimens in this area.

Long-term Bering Sea environmental variability revealed by a centennial-length biochronology of Pacific ocean perch Sebastes alutus

The productivity and functioning of Bering Sea marine ecosystems are tightly coupled to decadal-scale environmental variability, as exemplified by the profound changes in community composition that followed the 1976-1977 shift from a cool to a warm climate regime. Longer-term ecosystem dynamics, including the extent to which this regime shift was exceptional in the context of the past century, remain poorly described due to a lack of multi-decadal biological time series. To explore the impact of decadal regime shifts on higher trophic levels, we applied dendrochronology (tree-ring science) techniques to the otolith growth-increment widths of Pacific ocean perch Sebastes alutus (POP) collected from the continental slope of the eastern Bering Sea. After crossdating, 2 chronology development techniques were applied: (1) a regional curve standardization (RCS) approach designed to retain as much low-frequency variability as possible, and (2) an individual-detrending approach that maximized interannual synchrony among samples. Both chronologies spanned the years 1919-2006 and were significantly (p < 0.001) and positively correlated with sea surface temperature (March-December). The RCS chronology showed a transition from relatively slow to fast growth after 1976-1977. In both chronologies, the highest observed growth values immediately followed the regime shift, suggesting that this event had a critical and lasting impact on growth of POP. This growth pulse was, however, not shared by a previously published yellowfin sole Limanda aspera chronology (1969-2006) from the eastern Bering Sea shelf, indicating species- or site-specific responses. Ultimately, these chronologies provide a long-term perspective and underscore the susceptibility of fish growth to extreme low-frequency events.

Otolith biochronologies reveal latitudinal differences in growth of Bering Sea yellowfin sole Limanda aspera

Annual growth patterns in the hard parts of marine organisms are often related to factors in the physical environment; investigators are increasingly borrowing methods from the field of dendrochronology (tree-ring science) to explore these relationships. When applied to otoliths of yellowfin sole Limanda aspera, an abundant and commercially important flatfish, this approach has demonstrated a strong positive correlation between otolith growth and bottom temperature in the southeastern Bering Sea. In the present study, we assess whether the biochronology–growth relationship extends to yellowfin sole collected at higher latitudes. Two new northern Bering Sea biochronologies, one from the Bering Strait region and one near St. Matthew Island, were developed and compared with the southeastern Bering Sea biochronology using mixed effects modeling. Despite large distances (up to 600 km), a high degree of synchrony was observed among all three chronologies. However, subtle differences in growth among the three regions were revealed upon closer examination. The relative amplitude of otolith growth differed among the three chronologies, with stronger negative anomalies in the south and stronger positive anomalies in the north. Differences in average length at age were also detected, with fish growing slower to greater lengths at higher latitudes. Lastly, the Bering Strait biochronology had the weakest and most localized relationships with climate variables, suggesting effects of climate may not be felt uniformly across the regions examined. Biochronologies may thus provide a useful tool in evaluating potential biological responses to projected climate change across a species’ range.

Feeding and trophic status of yellowfin sole Limanda aspera (Pleuronectidae)

Feeding of yellowfin sole Limanda aspera is studied in the Sea of Okhostsk and Bering Sea in summer–autumn. Age variation of the food spectrum is analyzed with consideration of ecological characteristics of prey. By the composition of food, the sole is a benthophage–polyphage: it consumes Mollusca, Polychaeta, Echiuridea, Amphipoda, Decapoda, Pisces, Priapulida, Echinodermata, and Mysidacea. Depending on individual length, the values of trophic level vary within 3.06–4.56 and define it as a consumer of the second and third order. During the first year of life, the principal source of organic matter for the yellowfin sole is the pasture trophic chain. After transition to the bottom mode of life, it is changed into a detrital one. Predominant feeding on leading groups of the infaunal and onfaunal invertebrates result in biotic success of this species expressed in a leading position among Pleuroctiformes and other bottom fish belonging to the detrital network.

Updated Maturity Estimates for Flatfishes (Pleuronectidae) in the Eastern Bering Sea, with Implications for Fisheries Management

AbstractFemale Yellowfin Sole Limanda aspera, Alaska Plaice Pleuronectes quadrituberculatus, and Flathead Sole Hippoglossoides elassodon were collected from the eastern Bering Sea during known prespawning, spawning, and postspawning periods in 2012 and 2013, and their ovaries and otoliths were sampled for use in histological analysis to update historical maturity estimates. For fisheries management, new information on maturity at age can lead to possible changes in estimated reproduction potential (measured as female spawning stock biomass [SSB]) and values of fishing mortality reference points. Our analysis indicated that Yellowfin Sole currently mature at an age similar to that estimated in a study conducted 20 years ago. An evaluation of impacts on the stock assessment indicated that updated estimates of Yellowfin Sole SSB were over 7% higher, but the reference points only changed slightly. The first histologically derived maturity estimates for Alaska Plaice were close to the anatomically derived estimates (visual assessments from 1987), resulting in a marginal decrease (5%) in SSB, but changes in reference points were near 10%. Based on the new maturity estimates for Flathead Sole, SSB estimates increased by 7% compared with estimates currently used in the stock assessment, which relied on maturity data collected in 1999 and 2000. The change in Flathead Sole SSB was concomitant with changes of 16–18% in fishing mortality reference points. Our results indicated minimal differences from historical maturity estimates after re‐examination, but in some cases those differences led to relatively large changes in the respective reference points, underscoring the reference points' sensitivity to changes in maturity. Incorporation of these new maturity estimates into the stock assessment process provides valuable updated information for fisheries managers. However, a more comprehensive sampling program is needed to investigate the spatial and temporal aspects of reproduction for each species.Received November 13, 2014; accepted September 3, 2015

Sex-age structure and reproduction of yellowfin sole &lt;i&gt;Limanda aspera &lt;/i&gt;in the eastern part of the Okhotsk Sea

Data on sex ratio and size-age composition of yellowfin sole Limanda aspera Pallas [1814] in the eastern Okhotsk Sea are generalized. The sex structure is significantly different for mature and immature parts of this stock. Natural losses of both males and females depend on their year-class strength: the stronger the generation, the higher mortality. Besides, their maturing depends on the year-class strength, too: both males and females of high-abundant generations mature later, and rate of their gonads maturation decreases for elder age groups. Favorable environmental conditions supposedly promote growth of spawning stock with increasing of the females portion. So, for weak or mediate year-classes the leading increase of females provides an abundant recruitment at the beginning, but further the growing misbalance of sex ratio can effect on the reproduction negatively. However, dynamics of progeny correlates stronger with spawning stock than with sex ratio.

Scale-dependent detection of the effects of harvesting a marine fish population

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 444:251-261 (2012) - DOI: https://doi.org/10.3354/meps09434 Scale-dependent detection of the effects of ­harvesting a marine fish population Valerio Bartolino1,2,*, Lorenzo Ciannelli3, Paul Spencer4, Thomas K. Wilderbuer4, Kung-Sik Chan5 1Marine Research Institute, Department of Aquatic Resources, Swedish University of Agricultural Sciences, Lysekil 45321, Sweden 2Regional Climate Group, Department of Earth Sciences, University of Gothenburg, 40530 Gothenburg, Sweden 3College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA 4Alaska Fisheries Science Center, NOAA, Seattle, Washington 98115, USA 5Department of Statistics and Actuarial Science, University of Iowa, Iowa City, Iowa 52242, USA *Email: valerio.bartolino@slu.se ABSTRACT: Certain ecological processes dominate others at particular scales, and the response of populations to exogenous and endogenous forces are typically scale dependent. In spite of this central role played by scale, the temporal and spatial scales of human impacts on ecosystems and populations remain almost unknown. We applied a multiscale regression analysis to investigate the spatiotemporal scales which characterize the fisheries exploitation of yellowfin sole Limanda aspera in the Bering Sea. We found that harvesting affects the abundance of this species simultaneously at local and regional scales. At the local scale harvesting produced a negative effect on local fish densities, particularly in those areas and seasons of high fish aggregation, when both the vulnerability of the fish and the fishing effort increase. At the regional scale harvesting was characterized by a widespread negative effect on the whole fish population. Our findings demonstrate that (1) detection of the fisheries exploitation effects on natural populations is sensitive to the scale of investigation, (2) fisheries harvesting can simultaneously affect multiple ecological scales which are not linearly correlated with each other. We developed analytical techniques for the detection of scale-dependent processes, which can be readily applied to other systems. Our results provide insights on the risks of extrapolating the effects of harvesting on natural populations across scales, making the issues of scale and space central to the management and conservation of natural populations. KEY WORDS: Spatial distribution · Local exploitation · Regional exploitation · Scale · Yellowfin sole · Bering Sea Full text in pdf format Supplementary material PreviousNextCite this article as: Bartolino V, Ciannelli L, Spencer P, Wilderbuer TK, Chan KS (2012) Scale-dependent detection of the effects of ­harvesting a marine fish population. Mar Ecol Prog Ser 444:251-261. https://doi.org/10.3354/meps09434 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 444. Online publication date: January 10, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Distribution of ichthyoplankton in the eastern Peter the Great Bay, Sea of Japan, in June and July of 2007

Comparison of the results of ichthyoplankton surveys conducted at 97 stations in the eastern part of the Peter the Great Bay of the Sea of Japan, in June–July 2007 with the similar research data of the 1950s shows that at present, as was the case 50 years ago, flatfish eggs belonging mainly to the yellowfin sole Limanda aspera and brown sole Pleuronectes herzensteini prevail in the local ichthyoplankton (up to 86%). The highest concentrations of these species’ eggs were recorded in the Vostok Bay and Strelok Bay. The spawning activity of flatfish in 2007 is found to be lower than in the mid 1900s, but the significance of the eastern part of the Peter the Great Bay for flatfish reproduction remains large. The importance of long-term monitoring in this area, which is being subjected to steadily growing anthropogenic impacts, is also proven.

Effects of water temperature on prey-predator interactions of yellowfin sole Limanda aspera.

The dynamics of trophic relationships between prey and predator of yellowfin sole and influence of bottom water temperature upon them were examined in the eastern Bering Sea during summers from 1979 to 1984. Yellowfin sole were classified by sex and fork length. Mutual occurrences between yellowfin sole (male 11-25cm, female 16-20, 26-30cm) and capelin were found to vary with bottom temperature significantly. Area overlaps between yellowfin sole and most species were not correlated with ambient temperature. This fact suggests that mutual occurrence is due to other biological or physical considerations related to the intrinsic requirements of each species. This study has elucidated that some coexistences of prey and predators which facilitate predation to a greater degree were affected by bottom water temperature.

コガネガレイ筋肉のゼリー化ならびにプロテアーゼ活性と粘液胞子虫との関連

Numerous spores of a myxosporidian parasite, tentatively classified as the genus Kudoa, were found in many of the muscle spcimens of the yellowfin sole Limanda aspera which were caught in the Bering Sea. The muscle infected heavily with the parasite, displayed a considerably high protease activity. Such muscle was observed to be easily jellified when left standing at room temperature. Two types of protease occurred in the heavily infected muscle, one designated protease A hydrolyzing hemoglobin optimally at PH 3 and the other designated protease B casein optimally at PH 6.5 under the conditions applied. Protease B activity was not always detected in less infected muscles. The muscle containing both proteases was jellified very rapidly. Both protease activities were strongly inhibited by Hg+2, PCMB or leupeptin, indicating them to be of thiol enzyme. It was concluded from these results that the proteases were produced by the parasite and responsible for the jellification of the muscle.