Study of Fish Community in Ulak Lia Lake Sekayu, Musi Banyuasin Regency

This study aims to determine fish's diversity, abundance, and dominance in Ulak Lia Lake, Sekayu District. This research was conducted at Lake Ulak Lia, Sekayu District, Musi Banyuasin Regency, from February to March 2021. The fish sampling method was performed by direct catching at three predetermined observation stations using nets. Netting was carried out for 12 hours, taking catches with traps that have been installed in the morning from 7 a.m. to 9 a.m., depending on conditions or weather. Sampling was marked using a bamboo buffer and the help of the Global Positioning System (GPS). The results showed that the Diversity Index ranged from 1.85 to 1.91 indicating low diversity. The fish abundance index ranged from 30.16 to 36.87 indicating low fish abundance. Where the Dominance Index 0.71-0.72 shows a moderate dominance index. Meanwhile, the dominant fish in Ulak Lia Lake is the Sapil fish (Helostoma temminckii).

Growth and Hepatic Insulin-Like Growth Factor-I Gene Expression in Dominant and Subordinate Oreochromis Niloticus L Under Limited Period of Physical Interaction

Social stress is known to regulate several aspects of the teleost physiology. This study explored the influence of limited period of physical interaction on growth and hepatic insulin-like growth factor-I (IGF-I) messenger RNA (mRNA) expression of the fish. Twenty all-male Oreochromis niloticus were isolated for 10 days and were used in a social pair study. After the social interaction was settled, dominant and subordinate individuals in a pair were reared separately in one aquarium separated by glass divider. The fish were fed at the same rate daily to remove the possible effect of nutrition. The glass divider was removed 10 min daily for social interaction. Weight was monitored on Days 2, 7 and 14 during the experimental period, then hepatic IGF-I mRNA expression was quantified. During the 14 days social experiment, mean specific growth rate of dominant fish (1.6%·day−1) was significantly higher (P<0.01) than that of the subordinate fish (0.9%·day−1). Dominant fish also had 2.5 fold significantly higher (P<0.05) mean IGF-I mRNA expression than that of subordinate fish. These indicate that even under limited period of physical contact but with period of visual communication, social status regulates growth and hepatic IGF-I gene expression in this species of fish. There was also a significant positive correlation (r = 0.52; P<0.01) between growth and IGF-I mRNA level which supports the previous studies that hepatic IGF-I gene expression has a potential utility as an instantaneous growth rate indicator for O. niloticus.

Changing winter diet of thick-billed murres Uria lomvia in Southwest Greenland, 1990s versus 2010s

Southwest Greenland constitutes an internationally important wintering area for seabirds, including thick-billed murres (Uria lomvia Linnaeus, 1758), but their prey may be affected by the general warming of this sub-Arctic region. We compare murre diet collected in winter in the 1990s and 2010s around Nuuk. Fish made up 36% of the diet (wet mass) and crustaceans 63% in the 1990s, changing to 22% and 78% in the 2010s, respectively. Capelin (Mallotus villosus Müller, 1776) was the dominant fish species, and the smaller contribution in the 2010s coincided with declining densities of capelin around Nuuk. The crustaceans were dominated by two krill species, Meganyctiphanes norvegica M. Sars, 1857, and Thysanoessa inermis Krøyer, 1846. However, M. norvegica was only important in the 2010s (51% wet mass), while T. inermis was dominating the 1990s with 62% wet mass and only 23% in 2010s. The dominance of M. norvegica in the 2010s confirmed our expectations of a gradual “borealization” of this region due to the generally warming sub-Arctic. The smaller contribution of fish in the diet may also support the hypothesis of deteriorating winter conditions for murres. Apart from the diet, plastic was found in 15% of the birds and 53% had parasitic nematods.

Utilization of FAD Distribution in South Buton Waters as a Fishing App by Purse Sein Fishermen in Kadatua District, Selatan Buton Regency

Fish Aggregating Devices (FAD's) have long been used by fishermen in South Buton Regency. This study aims to determine the utilization of FAD distribution as a fishing aid by purse sein vessels in the waters of Kadatua District, South Buton Regency. This study aims to determine the utilization of FAD distribution as a fishing tool by purse sein vessels in Kadatua District, South Buton Regency. Data collection methods include FAD point data taken from GPS (Global Position System) fishermen and dominant catch data from purse sein fishermen. The results of the study obtained data on the distribution of FADs in Kadatua District spread between a distance of 0-12 miles, during the study the coordinates of FADs were obtained as many as 79 coordinate points owned by fishermen in Kadatua District. FADs used by purse sein fishermen to carry out fishing operations have 24 FAD points, which are spread over a distance of 0 – 12 miles. In April the distribution of FADs used as fishing aids by purse sein vessels was at a distance of ± 0 – 12 miles, while in May and June FADs used as fishing aids were at a distance of ± 2 – 12 miles. The dominant fish catch data for purse sein fishermen is 690 kg in April, 525 kg in May and 735 kg in June. The dominant catch during the study was dominated by scad fish (Decapterus spp). The level of effectiveness of the dominant catch of purse sein fishermen is highest at a distance of 4-12 miles with a total catch of 1,070 kg of the total catch of 1,950 kg.

A Study on the Characteristics of Fishery Resources Distribution in Coastal Waters of Yeongil Bay Using Acoustic Survey

In this study, the identification of dominant fish species in the East Sea was conducted using the dB-difference method. The survey was conducted using the two frequencies of 38 and 120 kHz in transect 6 of the southern part of the East Sea. Information on fish species was identified using fishing gear and e-DNA, and the dominant target fish species were selected and analyzed as cod, anchovy, common squid, and herring. The dB-difference range for each fish species was set to −0.86 dB < ∆MVBS 38–120 kHz < 0.82 dB for cod and to the range of 2.66 dB < ∆MVBS 38–120 kHz < 2.84 dB for anchovy. The dB-difference of the common squid was set to −0.36 dB < ∆MVBS 38–120 kHz < 1.25 dB and to the range of 0.88 dB < ∆MVBS 38–120 kHz < 2.28 dB for herring; the fish species were then identified in the echograms. When comparing the results of swimming depths by fish species and previous studies, cod was detected mainly at the bottom of the sea, and anchovy and common squid were detected mainly at a depth of 50 m. Herring was detected to be mainly distributed in water depths from 50 to 150 m.

Ichthyofauna Checklist in Tributaries of Muda Reservoir, Kedah, Peninsular Malaysia

Ichthyofauna checklist was scrutinized in tributaries of Muda Reservoir. A total of 5998 specimens were caught using a cast net of 2.5 cm mesh size. Amongst these specimen, 30 fish species from 12 families were recorded. The most dominant fish family in this lotic ecosystem was Cyprinidae. Rasbora dusonensis, Cyclocheilichthys apogon and Mystacoleucus marginatus recorded the uppermost distribution compared to other fish species found in this tributaries. Six fish species were the newly recorded species found in tributaries of Muda Reservoir; Barbonymus gonionotus, Luciosoma setigerum, Toxabramis houdemeri, Mystus singaringan, Anabas testudineus and Trichopodus pectoralis. In accordance with the previous combination of recorded fish species in tributaries of Muda Reservoir, a total of 57 updated total numbers of fish species were recorded. The information obtained in present study will update the latest ichthyofauna checklist in tributaries of Muda Reservoir, as well as for the future comparison in other geographical locations.

Determining seasonal dominant fish eggs and larvae species groups in the west of Tonkin Gulf

From 2003 to 2016, 1,649 samples were collected, covering both the time and space of the Gulf of Tonkin. The results have identified groups of seasonal dominant fish eggs and larvae: Seven species groups in Spring, nine species groups in the Summer, six species groups in Autumn, and four dominant species groups in the Winter. The dominant index (Yi) ranges from 0.02 to 0.26 depending on the species group and each season of the year, the highest in the Goby group - Gobiidae (Yi = 0.26) achieved in the Spring, followed by Herringgroup - Clupeidae reaches Yi = 0.20 in the Summer and the Anchovy group - Engraulidae reaches Yi = 0.16 in the Summer. The highest advantage index is only Yi = 0.09 in the Winter for Unicorn cod species - Bregmaceros macclelandi. During this period, the number of taxa and dominant indexes tended to decrease from Spring to Winter slightly.

Elevated cortisol lowers thermal tolerance but results in limited cardiac remodelling in rainbow trout (Oncorhynchus mykiss) experiencing chronic social stress

Juvenile rainbow trout (Oncorhynchus mykiss) held in pairs form dominance hierarchies in which subordinate individuals experience chronic social stress accompanied by lowered thermal tolerance (assessed as the critical thermal maximum, CTmax). Here we tested the hypothesis that chronic elevation of circulating cortisol levels reduces thermal tolerance in subordinate trout. In support of this hypothesis, subordinate trout that recovered from social stress for 48 h, a period sufficient to return cortisol to normal baseline levels, no longer showed reduced CTmax. Further, thermal tolerance was not restored in subordinates treated with cortisol during recovery from social stress. To explore possible mechanisms underlying the effect of chronic stress on CTmax, we also tested the hypothesis that chronic cortisol elevation induces cardiac remodelling in subordinate trout, as previously reported for cortisol-treated rainbow trout. Ventricle mass and cardiac hypertrophy markers were unaffected by social stress. Picrosirius red staining revealed a trend for lower collagen levels in the ventricles of subordinate relative to dominant trout. However, collagen type I transcript and protein levels, and markers of collagen turnover were unaffected. Indicators of cardiac function, including ventricle passive stiffness and intrinsic heart rate (fH), similarly were unaffected. In vivo fH was also similar between subordinate and dominant fish. Nevertheless, in keeping with their lower CTmax, subordinate fish exhibited cardiac arrhythmia at significantly lower temperatures than dominant fish during CTmax trials. Thus, high baseline cortisol levels in subordinate trout result in lowered thermal tolerance, but 5 d of social stress did not greatly affect cardiac structure and function.