Fishes

12 pages, 933 KiB

Open AccessArticle

Expression Conditions of Melanogenic Enzymes and Immune Molecular Markers in Atlantic Salmon Muscle During Different Productive Stages

by Raúl Cortés, Cristián A. Valenzuela, Andrés Johnson, Ariel Valenzuela, Juan Antonio Valdés and Sebastián Escobar-Aguirre

Fishes 2025, 10(7), 302; https://doi.org/10.3390/fishes10070302 - 20 Jun 2025

Abstract

Melanosis, or melanized focal changes (MFCs), is a significant issue in the Atlantic salmon (Salmo salar) farming industry, causing economic losses due to fillet downgrading. Nevertheless, molecular mechanisms underlying melanosis remain poorly understood, particularly in Chilean aquaculture. This study aimed to characterize transcriptional regulation associated with melanogenesis and inflammation in salmon muscle tissues exhibiting melanosis. Samples were collected from fish at three productive stages, all with MFCs in muscle in common: freshwater at two different origins and accumulated thermal units “ATUs” (300 ATUs post-antibiotic overdose, “Security”; 600 ATUs post-vaccination, “Vaccination”) and seawater harvest (“Harvest”). Gene expression analysis by qPCR targeted melanogenesis-related genes (mitf, tyr, and dct) and immune markers (arg2, inos2, and il-1β). Results revealed significant transcriptional modulation in freshwater samples, including downregulation of mitf, upregulation of dct, and changes in immune-related genes (arg2 and inos2). In contrast, seawater (“Harvest”) samples showed significant upregulation of tyr and dct, but no significant immune gene modulation. These findings indicate distinct molecular responses depending on the MFCs’ development stage, emphasizing early stages as critical points for intervention. Unlike recent studies, which have predominantly focused on samples from the harvest stage, this work uniquely integrates results from both the freshwater phase and the harvest stage. Full article

(This article belongs to the Section Welfare, Health and Disease)

28 pages, 3009 KiB

Open AccessArticle

Measurement, Spatiotemporal Evolution, and Spatial Spillover Effects of Carbon Sinks and Emissions from Shellfish and Algae Mariculture in China

by Han Zeng, Xuexue Wu, Xiaoyu Chen and Haohan Wang

Fishes 2025, 10(7), 301; https://doi.org/10.3390/fishes10070301 - 20 Jun 2025

Abstract

Under carbon emission reduction constraints, accurately assessing the spatial–temporal
patterns and drivers of mariculture carbon emissions and sinks is critical for promoting
marine economic development and achieving carbon neutrality. This study reviews key
components of China’s mariculture carbon and analyzes provincial data from 2008 to 2023
using econometric models to estimate emissions, sinks, and net carbon values. Spatial
heterogeneity and spillover effects are examined through geographically weighted
regression, Moran’s I, and spatial Durbin models. The findings indicate the following: (1)
Both direct and indirect mariculture carbon emissions are rising, with indirect emissions
growing faster, notably in Shandong, Fujian, and Guangdong. (2) Shellfish carbon sinks
generally dominate; algal carbon sinks are growing rapidly, especially in Fujian, Zhejiang
and Shandong. (3) Net carbon values vary by region—positive in Liaoning, Hebei,
Shandong, and Hainan, and negative in Jiangsu, Zhejiang, Fujian, Guangdong, and
Guangxi. (4) Energy intensity increases emissions; industrial upgrading reduces them.
Technological innovation, energy intensity, and ecological constraints enhance sinks. (5)
Emission spillovers are positive for energy and negative for structure; sink spillovers are
positive for energy and negative for technology; ecological effects are insignificant.
Overall, shellfish and algae mariculture play a key role in China’s marine carbon
sequestration. Regionalized carbon governance is essential to balance emissions–sinks,
and to advance low-carbon mariculture. Full article

(This article belongs to the Section Fishery Economics, Policy, and Management)

16 pages, 1216 KiB

Open AccessArticle

Stock Assessment of Long Whisker Catfish (Mystus gulio): Ensuring the Fisheries’ Sustainability in the Sundarbans Mangrove, Bangladesh

by Md. Tanvir Rahman Ovi, Tanni Sarkar, Dwipika Gope, Rayhan Ahmod, Sanzib Kumar Barman, Md. Mostafa Shamsuzzaman, Mohammad Mojibul Hoque Mozumder, Petra Schneider and Partho Protim Barman

Fishes 2025, 10(7), 300; https://doi.org/10.3390/fishes10070300 - 20 Jun 2025

Abstract

The world’s largest mangrove, Sundarbans, Bangladesh, is the habitat of the euryhaline catfish Nona Tengra (Mystus gulio). This study aimed to assess the stock status of M. gulio and provide reference points for sustainable fisheries’ management. One-year length–frequency (LF) data were collected from the Sundarbans region of Bangladesh and analyzed using the Length-Based Bayesian Biomass (LBB) method and the Length-Based Spawning Potential Ratio (LBSPR) model. The findings showed healthy biomass (B/B_MSY = 1.2), with 57% of the wild stock of this species being harvested (B/B₀ = 0.43). The calculated fishing mortality ratio indicated the underfishing conditions (F/M = 0.9). Safe exploitation (E = 0.46) was depicted, as E was smaller than the permitted level of 0.5. The value of capture length (L_c = 12.8 cm) was larger than the optimum capture length (L_{c_opt} = 10.0 cm) and the optimum length for maximum yield per recruit (L_opt = 12.0 cm) and larger than the maturity length (L_m = 9.16 cm), indicating the capture of mature individuals. The calculated Spawning Potential Ratio (SPR = 48%) was higher than the target reference points (SPR = 40%). This research evaluated the sustainable stock status. Although the margin between L_{c_opt} and L_m is very narrow, setting the minimum capture size at L_opt would be a conservative buffer to ensure long-term sustainability. The recommended minimum harvest size is 12 cm for M. gulio. Current fishing gear selectivity can ensure the sustainability of M. gulio in Sundarbans, Bangladesh; however, maintaining current fishing practice through careful management is suggested. Further assessments with length-based and other low-data methods should be conducted to refine exploitation estimates and trends. Full article

(This article belongs to the Section Biology and Ecology)

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25 pages, 8034 KiB

Open AccessArticle

The Impacts of Marine Heatwaves on Economic Fisheries in Adjacent Sea Regions Around Japan Under Global Warming

by Dan Liu, Xinjun Chen and Bilin Liu

Fishes 2025, 10(7), 299; https://doi.org/10.3390/fishes10070299 - 20 Jun 2025

Abstract

Climate change has significantly affected marine fisheries. In recent years, marine heatwaves (MHWs) have intensified concurrently with increasing sea surface temperature (SST), particularly along the coast of Japan in the Northwest Pacific. Although the relationships between MHWs and large-scale climate patterns are well established, the long-term effects of MHWs on fisheries remain uncertain. Considering thermal adaptability, we analyzed the catches of warm- and cold-water species from commercially important fisheries in adjacent sea regions around Japan, correlating them with regional SSTs and MHW indices. Our results show that regional SSTs exhibited a persistent increasing trend, with major shifts occurring around 1988/89 and 1998/99. Pronounced interannual–decadal variabilities were observed in the leading principal components (PCs) of different species groups, with step changes concentrated in 1989~1992, 1999~2003, and 2009~2012. Notably, there was a significant negative response of cold groups to warming SSTs. Among warm-water species, only the Japanese sardine (Sardinops melanostictus) catch exhibited a strong correlation with climate change. Gradient forest analysis and threshold generalized additive models (TGAMs) further revealed the nonlinear, threshold-driven responses of the fish groups to environmental variability, which occurred after step changes in both the environmental factors and catches. Matching analysis between the annual change rates of catches and MHW indices confirmed the detrimental effects of strong MHWs on marine fisheries. Full article

(This article belongs to the Section Environment and Climate Change)

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Fishes, Volume 10, Issue 7 (July 2025) – 4 articles

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