Sustainable Aquatic Research

Partial replacement of fishmeal with duckweed (Lemna minor) improves growth performance and body composition of Nile tilapia (Oreochromis niloticus) L.

Mary Opiyo — 2024-12-27

Duckweed (Lemna minor) was evaluated as an alternative protein source to fishmeal for Nile tilapia (Oreochromis niloticus) growth. Nile tilapia juveniles were fed experimental diet with L. minor supplementing fish meal at 0% (LM0), 5% (LM5), and 15% (LM15) and compared to a commercial diet as a positive control (COMM). The diets were administered to O. niloticus juveniles with an initial mean weight of 30.5 g stocked in cages in a pond at 30 fish per cage for 84 days. Growth performance, feed utilization, and body composition were evaluated and compared with those of the control. The final weight and specific growth rate were significantly higher in the fish fed the commercial diet than in LM15 when compared to LM0 (P < 0.05). The fish were able to utilize the L. minor-based feed well, although the feed conversion ratio was significantly lower in fish fed the LM15 and COMM diets (P < 0.05). Fish body composition was significantly affected by L. minor based diets. Protein content was significantly higher in fish fed the control diet and diet LM10 (P < 0.05), whereas lipid content was significantly higher in fish fed duckweed-based diets than in the control, with LM15 having the highest levels (P < 0.05). Partial replacement of fish meal with L. minor at 15% in the diet of O. niloticus is therefore recommended because it enhances growth performance, improves feed utilization, and increases the lipid content in Nile tilapia

Evaluating Water Quality in Northern and Eastern Coastal Zones of Sri Lanka: A Baseline Study for Environmental Monitoring and Conservation

Ramodh Niranga Jayawardena — 2024-12-27

The coastal area of Sri Lanka that accounts for nearly 1650 km stretch functions as a major source of livelihood, habitat, tourism, aquaculture, and trade. Although the coastal area offers a wide range of benefits to almost 55% of Sri Lanka’s Population, the coastal areas face severe threats due to factors such as aquatic pollution, coastal erosion, ecosystem degradation, urbanization, and sand mining. Therefore, to sustain the ecosystem stability and conserve of the coastal environment, it is crucial to conduct environmental monitoring of the coastal environment. However, a significant number of water quality assessments have been already carried out so far, only targetting the Western and Southern coastal zones of Sri Lanka. Therefore, this study intends to assess the marine water quality in selected locations (Total=26 Locations) in Northern (Mannar, Pooneryn, Kilinochchi, Jaffna, Mullaithivu) and Eastern (Trincomalee) coastal zones. Water samples were collected from these locations and both in-situ and laboratory analyses were carried out for Physico-chemical parameters (pH, Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Nutrients- Nitrates, Nitrites, and Ammonia, Turbidity, Total Dissolved Solids (TDS), Total Suspended Solids (TSS) following APHA standards. Based on the data collected, water quality was assessed using a Water Quality Index and R- statistical Programming software. The results show that statistically significant differences in TDS (P=0.004), COD (P= 0.036), and Nitrites (P=0.009) levels were found between all the locations during ANOVA, nevertheless no significant variation in COD during HSD test. The heat map analysis of water quality index model suggested that some of the locations in Mannar, Pooneryn, and Jaffna have indicated very poor water quality, while Trincomalee and Mullaithivu exhibited moderate to good water quality for selected locations. Overall, these results deliver us a clear picture to understand the current status of each of this selected location based on the water quality parameters. Therefore, it can be concluded that water quality monitoring and application of the water quality index approach should be carried out in each costal district to develop a database that can be inevitably referred to as baseline information during coastal ecosystem management, conservation efforts and even during any emergency case mitigation such as oil spills and ship fire incidents.

Gut analysis of the freshwater shrimp Caridina nilotica (“Ochong’a”) for its conservation in the face of its extensive utilization in aquaculture and climate change in Lake Victoria, Kenya

Elick Otachi — 2024-12-27

The aquaculture industry is expected to grow by double by the year 2050 but has not yet reached its full potential in East Africa. Tilapia makes up 75% of the freshwater fish production in Kenya, but the high cost of commercial fish feed is limiting the expansion of the industry. The freshwater shrimp Caridina nilotica is an established alternative to fishmeal in the production of the commercial feed, but its accessibility is limited to the natural stocks in Lake Victoria. Towards this end, this study investigated the gut contents of Caridina nilotica. One hundred specimen of C. nilotica were caught from Usoma Beach, in Winam Gulf of Lake Victoria. They were dissected and their gut samples were examined under a microscope. Every observed gut content were photographed and their frequency of occurrence recorded. Our findings showed that the main food for the C. nilotica was algae. The algal species were identified based on their morphology, color, and overall shape. The mean total body length of the examined C. nilotica was 2.12 ±0.29cm (±SD). Thirteen genera were identified from 6 divisions. The identified genus included; Microcystis sp., Surirella sp., Staurostrium sp., Synechococcus sp., Pediastrium sp., Synedra sp., Oocystis sp., Hantzschia sp., Oscillatoria sp., Fragilaria sp., and Glaucocystis sp. Merismopedia sp. (Cyanobacteria) and Botryococcus sp. (Chlorophyta) were abundant. C. nilotica mainly feed on algae from the division Chlorophyta, with diatoms and Cyanobacteria also being common. The information obtained in this study can be used to develop protocols for mass C. nilotica cultivation.

Investigation of The Presence of Escherichia Coli and Salmonella spp. in Seafood Sold in Izmir

Hatice Gündüz — 2024-12-27

Deniz ürünleri, çeşitli kültürlerde çiğ, kısmen pişmiş veya tamamen pişmiş olarak tüketilen değerli bir hayvansal protein kaynağıdır. Yüksek su ve protein içeriği ve neredeyse nötr pH'ı nedeniyle çeşitli mikroorganizmaların büyümesine elverişlidirler. Mikroorganizmalar taze yakalanmış deniz ürünlerinde bulunabilir ve taşıma, bağırsak çıkarma, balık tezgahlarında satış veya deniz ürünleri işleme sırasında eklenen maddelerden dolayı insanlardan çapraz kontaminasyon yoluyla bulaşabilir.

Salmonella, suda yaşayan organizmaların doğal mikrobiyotasının bir parçası değildir. Deniz ürünlerinde Salmonella bulunması, taşıma ve depolama sırasında dışkı kontaminasyonu veya çapraz kontaminasyon olduğunu gösterir. Escherichia coli genellikle dışkıyla kirlenmiş su veya yiyeceklerde bulunur ve kötü hijyenin bir göstergesidir.

Bu çalışmada İzmir’de satılan 50 su ürününde E. coli ve Salmonella spp. varlığı araştırılmıştır . Analiz edilen örneklerin 21’inde E. coli tespit edilirken, sadece 1 örnekte Salmonella spp. tespit edilmiştir. Toplam koliform sayısının 1,30 ile 5,85 log kob/g arasında değiştiği bulunmuştur. Bu sonuçlar su ürünlerinde önemli miktarda E. coli bulunduğunu ve fekal kontaminasyon düzeyinin ve dolayısıyla potansiyel tehlikenin yüksek olduğunu göstermektedir. Bu nedenle su ürünlerinin üretimi, dağıtımı ve satışı sırasında çapraz kontaminasyonu önleme çabalarının artırılması, hijyen ve sanitasyon uygulamalarına daha fazla dikkat edilmesi ve personel hijyenine özel önem verilmesi gerekmektedir.

Ecotoxicity of Aquaculture Chemotherapy-A Case Study in Chile

Patricio De Los Rios-Escalante — 2024-12-27

Aquaculture has experienced rapid growth in Chile over the past three decades, currently ranking first in America in terms of production. The use of chemotherapy, involving chemical drugs to prevent and treat disease outbreaks, has been widespread in salmon aquaculture for managing fish population diseases. To mitigate the negative environmental impacts of aquaculture chemotherapy, an analysis of the current legal framework governing Environmental Impact Assessments (EIAs) for veterinary medicinal products was conducted, referencing the Chilean regulatory framework (SAG 2011) and international guidelines (VICH 2000, 2004; EMA 2016). The analysis revealed a need to enhance the Chilean legal framework to align with international standards, thereby facilitating sustainable aquatic production. The study identified a legal framework that permits high ecotoxicity acceptance parameters, resulting in elevated environmental risk due to the use of Florfenicol in seawater-phase aquaculture, as indicated by a risk quotient (RQ) value exceeding 100.