Trachurus Research Articles

Digital Classification of Chilean Pelagic Species in Fishing Landing Lines.

Fishing landings in Chile are inspected to control fisheries that are subject to catch quotas. The control process is not easy since the volumes extracted are large and the numbers of landings and artisan shipowners are high. Moreover, the number of inspectors is limited, and a non-automated method is utilized that normally requires months of training. In this work, we propose, design, and implement an automated fish landing control system. The system consists of a custom gate with a camera array and controlled illumination that performs automatic video acquisition once the fish landing starts. The imagery is sent to the cloud in real time and processed by a custom-designed detection algorithm based on deep convolutional networks. The detection algorithm identifies and classifies different pelagic species in real time, and it has been tuned to identify the specific species found in landings of two fishing industries in the Biobío region in Chile. A web-based industrial software was also developed to display a list of fish detections, record relevant statistical summaries, and create landing reports in a user interface. All the records are stored in the cloud for future analyses and possible Chilean government audits. The system can automatically, remotely, and continuously identify and classify the following species: anchovy, jack mackerel, jumbo squid, mackerel, sardine, and snoek, considerably outperforming the current manual procedure.

Distribution and growth rates of Japanese jack mackerel <i>Trachurus japonicus</i> larvae relative to oceanographic conditions in the northern Satsunan area, southern Japan

Distribution and growth rates of Japanese jack mackerel <i>Trachurus japonicus</i> larvae relative to oceanographic conditions in the northern Satsunan area, southern Japan

Factors affecting biphasic degradation of eDNA released by Japanese jack mackerel (Trachurus japonicus)

Understanding environmental DNA (eDNA) persistence and degradation processes is necessary for the precise assessment of species distribution and abundance in marine environments via eDNA. Given the various particle sizes and persistence states of eDNA in water, biphasic degradation of eDNA, composed of its initial rapid and subsequent slower decay, may describe the fate of eDNA more precisely than monophasic degradation. However, it remains unclear which environmental factors influence eDNA decay rates at each decay phase. Here, the factors characterizing the biphasic degradation of eDNA were assessed by re-analyzing the dataset of a previous study, which estimated Japanese jack mackerel (Trachurus japonicus) eDNA decay rates using a monophasic decay model. A biphasic decay model was newly applied to the dataset, and the fitness was compared between decay models. Biphasic models were better fitted to the time-series decreases in Trachurus japonicus eDNA concentrations for all treatment levels. Moreover, eDNA decay rates significantly varied depending on temperature, fish biomass density, and genetic region, though only at the initial rapid phase. These results indicate the importance of microbial and enzymatic degradation of eDNA particles at the initial rapid phase. None of the variables significantly affected eDNA decay rates at the subsequent slower phase, which implies that microbial and enzymatic effect on eDNA degradation may be weakened during the decay phase. Further elucidating the effects of other environmental parameters (e.g., pH, dissolved oxygen, and UV level) on the biphasic eDNA degradation process would be helpful for a more precise understanding of the fate of eDNA considering its various states in water.

A mixed-species shoal including fewer heterospecifics is preferred by jack mackerel Trachurus japonicus juveniles

Mixed-species shoals of fishes were reported from various environments such as coral reefs and temperate lakes. The driving mechanism of forming mixed-species shoal can be either haphazard or a preferential choice by an individual. Here, we tested if jack mackerel Trachurus japonicus, a temperate marine pelagic fish, could choose a shoal composition using vision based on a choice experiment. Shoal preference of jack mackerel juveniles was evaluated by presenting shoals comprising one to four heterospecifics (half-lined cardinal Ostorhinchus semilineatus) out of four shoal members to the focal fish. When both conspecific and heterospecific shoals were presented to a single jack mackerel, the focal fish showed a preference for the conspecific rather than heterospecific shoal, indicating that they can choose a conspecific shoal based on the visual information. However, when a focal fish encountered both conspecific and mixed-species shoals including fewer heterospecifics (one out of four individuals), the latter was preferred. The result implies that jack mackerel can judge a preferable composition of shoal using visual information. The inclusion of fewer heterospecifics may be exploiting oddity effects, whereby minority species are exposed to relatively high vulnerability to predators, as well as resulting in reduced competition for food while maintaining predator vigilance in a shoal.

Trophic ecology of common bottlenose dolphins in a pelagic insular environment inferred by stable isotopes

The common bottlenose dolphin (Tursiops truncatus) is a top marine predator widely dispersed in coastal and pelagic habitats and with a generalist feeding behavior. Yet, information on the trophic ecology of animals inhabiting pelagic environments is still scarce. Using carbon (δ13C: 13C/12C) and nitrogen (δ15N: 15N/14N) stable isotope ratios, we identified and quantified the main groups of prey assimilated by bottlenose dolphins inhabiting an oceanic habitat (Madeira Island, East Atlantic). Bottlenose dolphins assimilated pelagic, schooling fish (such as blue jack mackerel, Trachurus picturatus) and mesopelagic and demersal squids, which reinforces the pelagic dietary composition of insular/oceanic dolphins. Also, intra-seasonal differences were found in their stable isotope ratios, which suggest intraspecific variability in the feeding behavior among individuals living in the same area. Sex was not the main factor contributing to these differences, suggesting the lack of trophic niche segregation between adult males and females in this offshore environment. Nonetheless, further studies including different life stages and information on the ecophysiological requirements are necessary to disclose the factors responsible for the observed variability. This study showed that insular dolphins fed primarily on economically important pelagic prey, highlighting the need of developing management strategies that integrate conservation in fisheries plans.

Replacement Effect of Fish Meal by Plant Protein Sources in Olive Flounder (Paralichthys olivaceus) Feeds with an Addition of Jack Mackerel Meal on Growth, Feed Availability, and Biochemical Composition.

Application of feed stimulants is very helpful to increase the feed intake of fish, especially in the development of low fish meal (FM) diets. FM replacement effect by various plant protein sources (corn gluten meal (CGM), soy protein concentrate (SPC), and corn protein concentrate (CPC)) in diets with an addition of jack mackerel meal (JMM) as feed stimulants on growth, feed availability, and biochemical composition of olive flounder was elucidated. An experimental design of two-way (two replacement levels (25% and 50%) × 3 replacement sources (CGM, SPC, and CPC)) analysis of variance was adopted. Seven diets were formulated. Amount of 60% FM was contained in the control (Con) diet. In the Con diet, 25% and 50% FM were replaced by CGM, SPC, and CPC with an addition of 12% JMM as feed stimulants, referred to as the CGM25, CGM50, SPC25, SPC50, CPC25, and CPC50 diets, respectively. Four hundred and twenty juvenile fish were distributed into 21 flow-through tanks. All diets were assigned to triplicate groups of fish. Fish were hand-fed to satiation twice a day for 56 days. Both dietary replacement levels and sources had statistical effect on weight gain (P < 0.0001 and P < 0.045, respectively), specific growth rate (SGR) (P < 0.0001 and P < 0.033), and feed consumption (P < 0.0001 and P < 0.03) of fish. Dietary increased FM replacement levels lowered weight gain, SGR, and feed consumption of fish. Weight gain, SGR, and feed consumption of fish fed the Con and CGM25 diets were statistically (P < 0.05) greater than those of fish fed the CGM50, SPC50, and CPC50 diets. Both replacement level and source had no statistical effect on feed utilization, biochemical composition except for statistical effect of replacement source on glycine content of fish, and lysozyme and superoxide dismutase (SOD) activities of fish. FM up to 25% could be substituted with CGM, SPC, and CPC in the olive flounder feeds supplemented with 12% JMM as feed stimulants without compromising growth, feed utilization, and lysozyme and SOD activities.

Inclusion effect of jack mackerel, Trachurus japonicus, meal in the diet of rockfish, Sebastes schlegeli, on growth, feed utilization, biochemical composition, and innate immune responses

AbstractDietary inclusion effects of various levels of jack mackerel meal (JMM) on growth, feed utilization, biochemical composition, and innate immune response of rockfish were determined. The control (Con) diet included 550 g/kg fish meal (FM). Ten, 30, 50, 100, 200, 400, 600, and 1000 g/kg of JMM were included in the Con diet, referred to as the JMM10, JMM30, JMM50, JMM100, JMM200, JMM400, JMM600, and JMM1000 diets, respectively. Eight hundred and ten fish (initial mean weight of 2.3 g) were distributed into 27 flow‐through tanks. The experimental diets were assigned to triplicate groups of fish. Fish were hand‐fed for 8 weeks. Weight gain of fish fed the JMM400 diet was statistically better than that of fish fed the Con, JMM10, JMM30, JMM50, JMM100, and JMM200 diets. Feed consumption of fish fed the JMM400 diet was statistically higher than that of fish fed the Con, JMM10, JMM30, and JMM50 diets. Dietary inclusion of JMM did not influence feed utilization, biochemical composition, and innate immune responses of fish. In conclusion, inclusion of JMM up to 400 g/kg of FM in diet improved growth and feed consumption of rockfish, and dietary optimum inclusion levels of JMM were estimated to be 396.7 and 403.1 g/kg based on regression analysis of weight gain and feed consumption, respectively.

Spatial estimation and yearly trends in abundance-index of Japanese jack mackerel (Trachurus japonicus) in the East China Sea and Sea of Japan

Catch per unit effort (CPUE) of commercial fisheries is recommended to be standardized because various factors can affect catch rates. Recently, the spatio-temporal analysis has been required to standardize fishery data, because catch is spatially distributed in proportion to fishery distribution and not in proportion to fish abundance. We developed the spatio-temporal models for the CPUE of large- and medium-sized purse seine fisheries for the different age groups of Japanese jack mackerel (Trachurus japonicus) to evaluate the potential spatial distribution and estimate the annual trends in abundance index. Japanese jack mackerel is widely distributed in the East Asian seas, including the East China Sea and Sea of Japan, and is an important fishery resource in Japan. Our models were delta-lognormal generalized additive mixed models that incorporated the temporal components of year and month, and size of fishing vessels as categorical variables, and the identity of the fishing vessels as a random variable. The spatial component represented by the latitude and longitude points of the fishing location was smoothed using an isotropic bivariate function. The water temperature at a depth of 50 m was incorporated to detect the effects of environmental factors. After all combinations of explanatory variables were evaluated, the model with the lowest Bayesian information criterion score was selected as the best model. All the best models among both binomial models and lognormal models contained all explanatory variables, although the best binomial model for age 2 exclude the vessel size and the best lognormal model for age 0 exclude the water temperature at a depth of 50 m. Our results indicate that the potential distribution areas for all ages of Japanese jack mackerel exist on the continental shelf in the southern part of the East China Sea, the western side of Kyushu Island, and along Honshu Island in the western part of the Sea of Japan. In contrast, the main distribution areas with higher density for age 0 were segregated into two: the southwestern East China Sea and the coastal area off Kyushu Island, although fish over age 1 were widely distributed. The standardized CPUE was higher than the nominal CPUE for age 0 from 2015 to 2020, and the standardized CPUE was also higher for age 1 in 2020. These results were derived from spatial models that compensated for the lack of spatial data due to the recent decrease in fishing operations in the Southeast China Sea. The yearly trends of standardized CPUE for each age could be used for the age-structured stock assessment model such as a tuned virtual population analysis. Improving the accuracy of the abundance index helps to further improve the reliability of stock assessments.

Large sardine resource discovered off south-eastern Australia: Potential risks, challenges and benefits of establishing a new fishery

This paper documents the discovery of a large sardine (Sardinops sagax) resource off South-eastern Australia. We use information from three ichthyoplankton surveys for jack mackerel to apply the Daily Egg Production Method (DEPM) to the South-eastern sardine stock. Mean daily egg production was estimated from survey data. Spawning area was estimated from the surveys and using a habitat suitability model to predict presence/absence of eggs in unsurveyed areas. Spawning biomass was calculated using adult parameters from the adjacent Southern stock. The spawning biomass in the area surveyed was 262,564 t (95% CI 125,670–326–438 t). Habitat modelling using a conservative threshold suggested that the total spawning biomass was 346,388 t (95% CI 143,936–548,840 t). These results suggest this stock has the capacity to sustain an annual catch of several tens of thousands of tonnes, which is considerably larger than the recent catch of < 2500 t. Our findings provide further evidence that opportunities exist to increase Australia’s fisheries production. Risks and challenges associated with establishing a new large-scale sardine fishery, including bycatch and ecological impacts, and opposition from conservation groups and recreational fishers are discussed. We also outline the potential socio-economic and environmental benefits, including the use of marine protein and oil from a sustainable local source with low environmental impacts as an input to the AU$1.3B Tasmanian salmon aquaculture industry. We emphasize the need to adopt a precautionary approach to developing a new fishery and the critical importance of conducting comprehensive surveys to confirm our findings and inform ongoing management.

Impacts of Strong ENSO Events on Fish Communities in an Overexploited Ecosystem in the South China Sea.

To better understand how fish communities respond to environmental changes under extreme climate events, we examine changes in fish communities in Beibu Gulf during strong El Niño and La Niña events. Strong La Niña and El Niño events affect the composition, abundance, and distribution of fish communities in Beibu Gulf. Fish community distribution and composition change before and after La Niña and El Niño events, and dominant species within them change with stable fishing intensity. The abundance and distribution of small pelagic fish such as Japanese jack mackerel (Trachurus japonicus) and Japanese scad (Decapterus maruadsi) are the most affected. Using a generalized additive model (GAM), we explore relationships between the abundance of T. japonicus and D. maruadsi and a suite of environmental variables. The GAM results revealed that sea surface salinity and sea surface temperature best explain changes in catch per unit effort of these two species during a La Niña event; depth, sea surface temperature, and mixed layer depth during an El Niño event. The results obtained in this study will offer support for implementing more-accurate, scientific fisheries management measures.

Hatch date and early growth of juvenile Japanese jack mackerel Trachurus japonicus caught in the Uwa Sea.

Development and growth rate variations during early life are important for understanding the mechanisms of recruitment dynamics. We examined the larval growth rate and age at the onset of metamorphosis (dm ) of juvenile Japanese jack mackerel recruited to a population in the Uwa Sea, Japan. Otolith microstructure analyses revealed that the hatch date of juveniles ranged from February to April in 2011-2015, and that their dm were 25.5-30.5 d and mean growth rates at the larval (GL ) were 0.30-0.34 mm d-1 . Among these, dm showed significant negative correlations with juvenile abundance. Moreover, the hatch date did not coincide with the spawning period of this species in the Uwa Sea, and the hatch date and mean growth rate at the larval stage were comparable to those of Japanese jack mackerel juveniles sampled in the East China Sea (ECS). These findings suggest that most juvenile Japanese jack mackerel originated in other waters, including the ECS, and that larval stage duration influence their recruitment abundance in the Uwa Sea. This article is protected by copyright. All rights reserved.

Effects of Biotic and Abiotic Factors on the Spatiotemporal Distribution of Round Scad (Decapterus maruadsi) in the Hainan Island Offshore Area

Fishery resource and environmental data from four surveys conducted in the Hainan Island offshore area from March 2021 to June 2022 were used to investigate the spatiotemporal distribution of round scad (Decapterus maruadsi). A generalized additive model was applied to explore the relationships among abundance and distribution, also biotic and abiotic factors (i.e., temperature, salinity, chlorophyll-a concentration, water depth, phytoplankton abundance, zooplankton abundance, and jack mackerel (Trachurus japonicas) abundance). Round scad abundance (average 67.17 kg/km2) showed distinct spatial and seasonal differences around Hainan Island, with highest abundance in summer (171.72 kg/km2) and lowest abundance in spring (3.06 kg/km2). The optimal model revealed that jack mackerel abundance, sea bottom temperature, sea surface temperature, and latitude very significantly (p &lt; 0.01) affected round scad distribution. Jack mackerel abundance (mainly in the range 0–50 kg/km2) was positively correlated with round scad distribution. The distribution showed a dome-shaped relationship with bottom water temperature in the range 18–30 °C, with maximum abundance at 24 °C. The distribution was negatively correlated with surface water temperature in the range 22–30 °C. Sea surface chlorophyll-a concentration and longitude were significantly correlated (p &lt; 0.05) with round scad distribution. The results provide theoretical support to further investigate the formation mechanism of round scad fishing grounds and to enrich knowledge of pelagic fish abundance in the continental-shelf waters of the northern South China Sea.

Detection of fish passing through a narrow path using reflected and transmitted ultrasonic waves

The properties of echoes and transmitted waves from a fish body in megahertz bands were investigated to construct a fish detection method in a narrow path using a simple measurement structure using a pair of transducers. Experiments were performed in a water tank using dead Japanese jack mackerel (Trachurus japonicus). From the echoes, the outlines of fish could be observed. High amplitudes of echoes from the swim bladder and fins were observed, while relatively low amplitudes of echoes were observed from other body parts, e.g., the head, body surface, and vertebral columns. From the transmitted waves, decreased amplitudes and times-of-flight in waves transmitted from the fish body were observed. The fish could be detected using ultrasound, in megahertz bands, and the combined use of the echo and transmitted waves could increase the information obtained about fish compared with the use of echoes only.

Age, Growth and Reproductive Cycle of the Jack Mackerel &lt;i&gt;Trachurus japonicus&lt;/i&gt; in the Southwestern Sea of Japan

The growth and reproductive cycle of the jack mackerel (Trachurus japonicus) that were caught in the southwestern Sea of Japan during 2016-2017 were examined based on otolith annuli and gonad histology. Translucent and opaque zones on transverse sections on otoliths were identified and opaque rings were counted. The von Bertalanffy growth curve was expressed as follows: FLt = 445{1 − exp (−0.149 (t + 1.74))} (0.250 < t < 7.67), where FLt is the fork length (mm) at age t. The estimated body length at age t in the growth model was smaller than that of jack mackerel in the East China Sea. The spawning period was evaluated from May to September based on the monthly changes in the gonadosomatic index and histological observations. The spawning period starts later than in the East China Sea, but the minimum size at first maturity was similar to that of the jack mackerel in the East China Sea. The information generated in this research can contribute to the sustainable management of the species in the Sea of Japan.

Population Genetics of Chilean Jack Mackerel, Trachurus murphyi Nichols, 1920, (Pisces, Carangidae), in Waters of the South Pacific Ocean

Estimating genetic diversity and population structure with polymorphic markers might provide information for the better management of fish that have economic importance. We used the Chilean jack mackerel, Trachurus murphyi, a pelagic species distributed in the south Pacific Ocean, to test the population genetic structure across its distribution. A total of 522 samples were collected from 11 locations in 2008, to be analyzed using six loci microsatellites. We conducted traditional genetic analyses to describe the genetic diversity of T. murphyi and whether it shows spatial genetic structure. The results showed a high genetic diversity across locations (Ho = 0.551 to 0.980; He = 0.676 to 0.959). Estimates for the population structure showed a low and non-significant pairwise FST in all comparisons. We supported the non-genetic differentiation previously reported with the used microsatellite panel. Further comparative temporal studies should be conducted to identify the stability of this pattern. Overall, this study reinforces the hypothesis that, in the Pacific Ocean, Chilean jack mackerel correspond to a large single population.

Complementary Role of Fishers' Experiential Knowledge to Conventional Science in Terms of Species-Specific Biological Traits and Population Changes in Azorean Waters.

Combining scientific information with fishers' perceptions may be a robust approach for directing decision-makers working with marine ecosystems. This is particularly the case when baseline data on a vulnerable stock are poor, as the integration of fishers' experiential knowledge can help fill data gaps, as well as inform legitimate management actions, and empower fishing communities in resource management. This study aimed to analyze fishers' knowledge regarding the biology (reproduction, growth, and maximum size) and temporal changes in the abundance and size of six commercially important marine species (red porgy Pagrus pagrus, veined squid Loligo forbesii, blue jack mackerel Trachurus picturatus, blackspot seabream Pagellus bogaraveo, blackbelly rosefish Helicolenus dactylopterus, and European conger Conger conger) in the Azores small-scale communities. Additionally, a comparison between fishers' knowledge and available scientific information was performed to determine the former's value and its possible complementarity with the latter. A total of 105 fishers were surveyed in the nine islands of the archipelago. The results demonstrated a reasonable level of agreement between the information from fishers and scientific literature on the species-specific spawning seasons and growth rates. The median values of size at maturity and maximum length were not statistically different between data sources. Most participants indicated size and abundance trends that were consistent with the literature. This study highlights the usefulness of fishers' perceptions in improving knowledge about species characteristics and temporal changes in commercially exploited stocks, especially when scientific research is limited, but further research should be encouraged to improve the reliability and consistency of these results.

Remote Sensing of the Subtropical Front in the Southeast Pacific and the Ecology of Chilean Jack Mackerel Trachurus murphyi

The Subtropical Front (STF) plays a key role in the ecology of Chilean jack mackerel Trachurus murphyi. Nonetheless, there are few remote sensing studies of the STF in the open Southeast Pacific, and almost all of them have been conducted by satellite oceanographers in Russia and Ukraine to support respective large-scale fisheries of jack mackerel in this region. We reviewed these studies that documented long-term seasonal and interannual variability of the STF from sea surface temperature (SST) and sea surface height (SSH) data. We also mapped the STF from satellite sea surface salinity (SSS) data of the SMOS mission (2012–2019). The Subtropical Front consists of two fronts–North and South STF about 500 km apart–that border the Subtropical Frontal Zone (STFZ) in-between. The STF is density-compensated, with spatially divergent manifestations in temperature and salinity. In the temperature field, the STF extends in the WNW to ESE direction in the Southeast Pacific. In the salinity field, the STFZ appears as a broad frontal zone, extending zonally across the entire South Pacific. Three major types of satellite data-SST, SSH, and SSS-can be used to locate the STF. The SSH data is most advantageous with regard to the jack mackerel fisheries, owing to the all-weather capability of satellite altimetry and the radical improvement of the spatial resolution of SSH data in the near future. Despite the dearth of dedicated in situ studies of the South Pacific STFZ, there is a broad consensus regarding the STFZ being the principal spawning and nursing ground of T. murphyi and a migration corridor between Chile and New Zealand. Major data/knowledge gaps are identified, and key next steps are proposed to mitigate the data/knowledge gaps and inform fisheries management.

An exceptional concentration of marine fossils associated with wood-fall in the Terhagen Member (Boom Formation; Schelle, Belgium), Rupelian of the southern North Sea Basin

A large fragment of driftwood was discovered in the marine Terhagen Member (Boom Formation, NP23) at Schelle (Belgium), representing the first well-documented case of wood-fall in the Rupelian of the North Sea Basin. This trunk with a side-branch, identified as Cupressinoxylon sp. (Cupressaceae), caused a large irregularity on the sea bottom, creating a unique microenvironment which allowed colonization by some taxa virtually absent elsewhere in the Boom Formation. The fossils were further concentrated in a silty lens against the trunk by the effects of prolonged wave-driven turbulence. This lens comprised a large set of compartmental plates of the turtle barnacle Protochelonibia hermani Gale sp. nov., possibly part of a single colony originally attached to a turtle. The material includes the best preserved plates of Protochelonibia known to date, yielding new information on the construction of its shell. Additionally, a disarticulated tooth set of 154 teeth of Carcharias contortidens (Agassiz, 1843) was found, the first such discovery in more than 100 years. An articulated dentition of this taxon, initially studied by Leriche (1910), is refigured herein. Some very rare valves of the bivalve Palliolum permistum (Beyrich, 1848) are identified and the gastropod Amblyacrum cf. roemeri (von Koenen, 1867) is reported here for the first time from the Belgian Rupelian. The teleost otolith assemblage comprises ca 30,000 specimens belonging to 11 species only, of which Trachurus reineckei Hoedemakers sp. nov. is new to science and Myoxocephalus primas (Koken, 1891) and Capros siccus Schwarzhans, 2008 are new for the Belgian Rupelian. The new species represents the earliest record of the thermophilic genus Trachurus in the Oligocene of the North Sea Basin. Liparis minusculus Nolf, 1977 is synonymized with Myoxocephalus primas, whereas Erythrocles ohei Schwarzhans, 1994 is transferred to the genus Trachurus.

Inclusion effect of jack mackerel meal as feed stimulants in diets replacing different levels of fish meal with various animal protein sources on growth performance of olive flounder (Paralichthys olivaceus)

Incorporated feed stimulants into fish feeds is a very sustainable aquaculture technique, especially in developing low FM diet to improve feed consumption and growth performance. This study aims to evaluate inclusion effect of jack mackerel meal (JMM) as feed stimulants in diets replacing different levels of FM with various animal protein sources on the growth, feed utilization, biochemical composition, and non-specific immune response of olive flounder (Paralichthys olivaceus). Two-way [3 substitution source; tuna by-product meal (TBM), chicken by-product meal (CBM), and meat meal (MM) × 2 substitution ratio; 25% and 50%] ANOVA experimental design was applied. Seven experimentally formulated diets were prepared. The control (Con) diet contained 60% FM. Twenty-five and 50% of FM in the Con diet were substituted with TBM, CBM, and MM when 12% JMM was included at the expense of FM, referred to as the TBM25, TBM50, CBM25, CBM50, MM25, and MM50 diets, respectively. All experimental diets were formulated to be isonitrogenous at 56.1% and isolipidic at 10.2%. Four hundred and twenty juvenile fish were randomly distributed into 21 flow-through tanks. Severn experimental diets were assigned to triplicate groups of fish. Both dietary substitution source and ratio had significant (P < 0.0001, P < 0.003, P < 0.0001, P < 0.003, P < 0.0001, and P < 0.0001, respectively) effects on weight gain, specific growth rate (SGR), and feed consumption of fish. Weight gain, SGR, and feed consumption of fish fed the Con diet was significantly (P < 0.0001) inferior to fish fed the TBM25, TBM50, and CBM25 diets. However, no significant (P > 0.05) difference in feed utilization, biochemical composition, and non-specific immune response of fish was observed among the experimental diets. Conclusively, TBM and CBM, and MM could be used as the proper substitutes for FM up to 50%, and 25%, respectively in olive flounder feeds with inclusion of JMM as feed stimulants.

A review of the family Cymothoidae (Isopoda: Cymothooidea) infesting marine fishes from Malaysian waters, with new host and geographical records.

A checklist of parasitic cymothoids from Malaysian waters is presented based on available literature and material collected from 2010 to 2020. Most of the collected specimens were recorded from waters of Terengganu, east coast of Peninsular Malaysia (facing the South China Sea), whereas literature records were included from Sarawak, along the Miri coast of northwest Borneo. The checklist comprises 19 species in ten genera, seven of which are new records from Malaysia: Anilocra nemipteri Bruce, 1987; Ceratothoa barracuda Martin, Bruce & Nowak, 2015; Ceratothoa carinata (Bianconi, 1869); Cymothoa epimerica Avdeev, 1979; Elthusa sigani Bruce, 1990; Joryma engraulidis (Barnard, 1936) and Renocila richardsonae Williams & Bunkley-Williams, 1992. Eight new host records are based on collected specimens: Anilocra nemipteri was dorsally attached on Nemipterus nemurus (Bleeker, 1857), Nemipterus nematophorus (Bleeker, 1854), Nemipterus tambuloides (Bleeker, 1853) and Nemipterus thosaporni Russell, 1991 (family Nemipteridae); Ceratothoa carinata was found in the buccal cavity of Decapterus macrosoma Bleeker, 1851 (family Carangidae); Cymothoa eremita (Brunnich, 1783) was attached in the buccal cavity of Nemipterus tambuloides (Bleeker, 1853) and Nemipterus furcosus (Valenciennes, 1830); Elthusa sigani was found attached on the gills of Pterois russelli Bennett, 1831 (family Scorpaenidae), and Renocila richardsonae was attached on the caudal fin of Upeneus japonicus (Houttuyn, 1782) (family Mullidae). All cymothoid species listed here are known to have a Central Indo-Pacific distribution, with some ranging as far as the Western Indian Ocean. A cymothoid-host association is here listed from 28 fish families, with the most commonly reported from Carangidae (pompanos, jack mackerels, runners, scads), Engraulidae (anchovies), and Leiognathidae (ponyfishes, slipmouths). This paper is the first comprehensive review of both verified literature records and deposited specimens. A key for the family of Cymothoidae in Malaysian waters is given.