Limnology and Freshwater Biology

Availability and Marketing System of Fish and Crustaceans in an Urban Fish Market: A Study on Retail Practices

Chakraborty, Smriti — 2025-06-11

The marketing system and structure significantly impact the socio-economic conditions and production systems of local communities. Hence, this study aimed to explore the diversity of fish and crustacean species and the marketing system in the urban fish market known as Alexander Fish Market in Lakshmipur. During the study, 32 fish species and 3 crustaceans were identified, representing 35 genera, 21 families, and 11 orders. The majority of species belonged to the orders Cypriniformes (family Cyprinidae) and Siluriformes (families Bagridae and Ailiidae). Among the recorded species, a total of 3 species have been reported as Endangered (EN), 3 as Vulnerable (VU), 4 as Not Listed (NL), 6 as Not Threatened (NT), and 19 as Least Concern (LC). The fish distribution chain involved intermediaries such as beparies, aratders, wholesalers, and retailers. Three types of marketing channels were identified in the study. The average marketing cost, income, and profit for retailers were BDT 97.14/day, BDT 792.71/day, and BDT 695.57/day, respectively. Fish pricing depended mainly on market structure, species quality, size, weight, and season. The average prices per kg for different fish species were recorded as follows: Ilish (BDT 1200±17.89), Ayre (BDT 915±8.64), Bacha (BDT 847±8.24), Ghagra (BDT 816±7.94), Khorsula (BDT 830±5.63), Golda Chingri (BDT 855±8.45), Bagdha Chingri (BDT 712±7.11), Chiring (BDT 715±6.15), and Gang Tengra (BDT 725±8.25). Major challenges in fish marketing included the use of unhygienic ice, lack of financial support from the government and NGOs, and poor knowledge of fish handling and transportation. Organizational and government support, along with extension services on fish preservation, handling, icing, and curing, are crucial for enhancing fish marketing and improving fish quality.

Eukaryotic communities of freshwater bryozoans (Phylactolaemata: Plumatellidae) of the Baikal region

Peretolchina, Tatiana — 2025-06-11

The diversity of eukaryotic communities associated with bryozoans was investigated using DNA metabarcoding based on the 18S rRNA gene. The results obtained indicate that each bryozoan species, coexisting in close proximity to one another, harbors a distinctive community of associated eukaryotes, the composition of which likely depends on the form of the colonies. The community associated with the “bushy” colony of Plumatella sp. was found to be more diverse and differed in species composition from the community formed on the “creeping” colony of P. repens. In the “bushy” bryozoans, diatoms (60%) and ciliates (22%) predominated, along with golden algae (4%), hydras (3%), chytridiomycetes (1.6%), and rotifers (1%). In contrast, unicellular algae (32%), dinoflagellates (27%), apicomplexans (10.6%), and other groups of protists (amoebas, euglenoids, and others) (4.6%) were more frequently associated with the “creeping” bryozoan. Among invertebrates, annelid worms (12.5%), tapeworms (4%), and mollusks (3%) predominated. Notably, the study revealed the presence of protostome animals belonging to the phylum Entoprocta, marking the first documentation of this taxon in the water bodies of the Baikal region.

Decoding the Influence of Water Quality and Seasonal Shifts on Phytoplankton Communities in Eastern Indian Freshwater Waterbodies

Garai, Sumanta — 2025-06-11

This study presents a comparative analysis of phytoplankton dynamics and ecological status across two freshwater ponds in Birbhum, West Bengal, India, for the two years (from April 2020 to March 2022). The two study sites included a fish cultivation pond (S1) and an agricultural waste pond used for irrigation (S2). Phytoplankton productivity and environmental parameters, including chlorophyll-a content, temperature, pH, dissolved oxygen (DO), biological oxygen demand (BOD), gross primary productivity (GPP), net primary productivity (NPP), and nutrient levels (nitrate, phosphate, ammonia, silicate, and chloride) were monitored. Both sites were exposed to similar temperature ranges (12°C to 38°C), but S2 was more alkaline than S1. Chlorophyll-a content ranged from 1.84 to 5.78 mg/L in S1 and 1.22 to 3.68 mg/L in S2. Nutrient concentrations peaked during post-monsoon period, supporting enhanced phytoplankton growth, and were minimum in summer for both sites. Principal component analysis revealed that nitrate, phosphate, and silicate were primary influencers for S1, while pH, nitrate, phosphate, ammonia, and chloride were influential for S2. GPP and NPP emerged as common factor in both ponds. Correlation analysis indicated that chlorophyll-a in S1 was positively associated with nitrate, phosphate, silicate, and GPP-NPP, whereas, in S2, it correlated positively with pH, nitrate, phosphate, ammonia, and chloride. The post-monsoon season exhibited the highest phytoplankton diversity, dominated by chlorophycean species in S1 and Euglenophyceae in S2, the latter likely due to elevated ammonia levels.

New locality records of invasive freshwater jellyfish Craspedacusta sowerbii (Lankester, 1880) in Türkiye

Seçer, Burak — 2025-06-11

Invasive jellyfish Craspedacusta sowerbii (Lankester, 1880) is a hydrozoan (Phylum Cnidaria, Class Hydrozoa), most easily identified in its hydromedusa form as a small, bell-shaped jellyfish. Indigenous to the Yangtze River valley in China, this species has spread across temperate climates, including Türkiye, for over a century. In this study, three new locality records were discovered in Türkiye: Umurbey (Çanakkale), Geyik (Muğla), and Seyhan (Adana) dams. Some physicochemical parameters (pH, dissolved oxygen, temperature and electrical conductivity) of the sampling points were measured. Although there is no definite information on the origin of this species in the dams, it is thought that it is hypothesized that it may have been introduced by fish stocking, aquatic birds and human activities.