Maharashtra plays a crucial role in India’s fish production, particularly through its robust marine fisheries sector. With a coastline stretching approximately 877.97 km along the Arabian Sea, the state is a major contributor to national seafood output (Government of India, 2025). Key coastal districts are Palghar, Mumbai, Raigad, Ratnagiri and Sindhudurg host numerous prominent landing centers, such as Pachubandar, Sassoon Dock, Versova, Alibag, Karanja and Mirkarwada.
       
According to the Government of India (2023), Maharashtra contributes approximately 6 to 8% annually to India’s total fish production, encompassing both marine and inland sectors. Global fish production is increasing at an average rate of 3.00 per cent annually and has peaked to 178.50 million tons with 156.40 million tons of fish being used for human consumption (FAO, 2020; Tiwari et al., 2023).  In 2022-23, Maharashtra recorded a total marine fish production of 4.46 lakh tonnes, underscoring its substantial role in the national fisheries landscape. Notably, dolnet operations accounted for 23.9% of Maharashtra’s total marine fish catch, contributing 0.307 million tonnes in 2011, underscoring their significant and sustained economic role in the state’s coastal fisheries (Kumawat et al., 2015).    
       
India’s marine fisheries sector comprises 1,66,333 fishing crafts, of which 25.8% (42,985) are mechanized, 58.7% (97,659) are motorized and 15.4% (25,689) are non-motorized. Among motorized crafts, 32.2% are equipped with inboard engines and 67.8% with outboard engines. In the mechanized segment, 71.5% of the crafts are trawlers, 15.2% are gillnetters and 8.0% are dolnetters or bag netters (Department of Fisheries MH and CMFRI, 2020).
       
Although dolnets are the most widely used traditional fishing gear in Maharashtra and play a pivotal role in the state’s fishery economy, systematic studies examining temporal variations in their catch composition remain limited (Pradhan et al., 2019). The dol net, a localized form of bag net is an indigenous gear type widely used along India’s northwest coast (Khileri et al., 2015). This fishing gear is also used in several other Asian countries such as Bangladesh, Indonesia, Malaysia, Myanmar and Thailand (Manojkumar and Dineshbabu, 1999). Dolnets are specifically designed to exploit strong semi-diurnal tidal currents and are commonly deployed along gently sloping continental shelves with sandy-muddy bottoms and moderate turbidity conditions prevalent along the Maharashtra and Gujarat coasts but absent along India’s eastern coast (Kurup and Devaraj, 1999). Even though dolnets dominate Maharashtra’s coastal fisheries, few studies have examined their seasonal catch dynamics, juvenile bycatch and environmental interactions. Juvenile bycatch refers to the incidental capture of immature individuals of commercially or ecologically important species that have not yet reached reproductive age or minimum legal size, leading to ecological and management concerns. Most research addresses gear operations or broad landings, while systematic documentation of design diversity, species composition and tidal influences at the district scale is lacking.
       
A key regional distinction lies in anchoring techniques: in Maharashtra, dol nets are fixed to poles embedded in the seabed to remain stationary in the water column maximizing catch efficiency by preventing escape. These nets are engineered to target species carried passively by ocean currents and their performance is highly dependent on environmental factors such as tidal amplitude and wind direction. Along the Saurashtra coast, stone heaps are commonly used instead of poles for anchoring (Manojkumar and Dineshbabu, 1999). As dolnet designs vary considerably across locations and time periods, yet there is no systematic documentation linking these design variations with their corresponding catch composition.
       
The present study aims to document the design features of dolnet gear operated in Raigad, the largest dolnet operating district of Maharashtra to evaluate species wise and season wise catch composition, juvenile bycatch and assess the influence of environmental parameters, especially tidal amplitude on catch abundance.

Study area
 
The study was conducted along the Maharashtra coast between January 2023 and October 2024. An experimental study focusing on catch composition analysis was conducted at Karanja region in Raigad district of Maharashtra, India (Fig 1).


 
Gear design documentation and catch sampling
 
Monthly surveys recorded dolnet gear characteristics such as net length, sectional structure, mesh gradation, yarn material, float, sinker and anchoring method. A total of 10 representative dolnet gears were studied to ensure standardized documentation. Mesh sizes at codends were measured using Vernier Caliper (0-150 mm; Resolution: 0.1 mm; Accuracy: ±0.02 mm). Fish samples were collected from dolnet operations to study the target species composition. Juvenile bycatch assessment focused on three dominant species: Harpadon nehereus, Coilia dussumieri and Acetes indicus, which hold economic significance in the region.
 
Experimental fishing trails at Karanja, Raigad district
 
Eighteen structured fishing trials were conducted across pre-monsoon (February to May), monsoon (August and September) and post-monsoon (October to January) seasons. Nets were deployed for 3 to 4 hours during peak tidal currents, typically coinciding with flood (high) tides. GPS coordinates for all experimental stations are listed in Table 1 (Tides4Fishing, 2024).


 
Sample handling and juvenile analysis
 
Collected fish specimens were preserved in 10% formalin in labeled containers for biometric and taxonomic analysis  (Chakraborty et al., 2006). Study was conducted at Mumbai Research Centre of ICAR-Central Institute of Fisheries Technology, Vashi, Navi Mumbai. Identification was based on standard taxonomic references (Munro, 2000; Talwar and Kacker, 1984; Talwar and Jhingran, 1991; Bavithra et al., 2024). Standard length (SL) for the top three fish species (Harpadon nehereus, Coilia dussumieri and Acetes indicus). Each month, a minimum of 50 specimens per species were recorded for length in centimeters. Juveniles were classified based on species specific minimum legal size (MLS) or length at first maturity (L_m) refers to the regulatory size limit prescribed for a species, below which capture and landing are prohibited to ensure that individuals reach maturity and contribute to spawning at least once before being harvested. Anulekshmi et al., (2018) reported that the minimum legal size (MLS) for Bombay duck (Harpadon nehereus) along the Maharashtra coast is 18 cm TL (total length).
 
Data analysis
 
Seasonal variations in species abundance, biomass and juvenile proportions were analyzed using R software v4.5.0 (Lafaye De Micheaux et al., 2013). CPUE was computed as total catch weight per standardized unit of fishing effort (Ricker, 1975). Where significant seasonal effects were detected, pairwise comparisons were conducted using Tukey’s HSD post-hoc test (Zar, 1999; Ahmed et al., 2016; Janarthanan et al., 2023). Relationships between tidal amplitude and total catch were examined through Pearson correlation analysis, while graphical outputs including bar plots, line graphs and scatterplots with fitted regression lines were generated to aid interpretation (Blaber, 2008).

Dolnet design variability across Maharashtra
 
To examine gear specific adaptations in dolnet operations, detailed documentation was undertaken for the Karanja dolnet design in Raigad district. This design is characterized by region specific modifications in net length, mesh gradation, codend structure and anchoring system, reflecting adaptations to the local hydrodynamic environment, fishing depth and dominant target species.
       
The Karanja dolnet (Fig 2) deployed in semi enclosed estuarine conditions, represents a compact five section design with mesh sizes tapering from 120 mm to 12 mm at the codend. Karanja dolnet construction prioritizes retention of small pelagic species such as Harpadon nehereus and Acetes indicus. However, this fine codend mesh poses a high risk of juvenile retention, echoing previous findings in estuarine creek fisheries where similar gear structures were associated with substantial bycatch of immature individuals (Pradhan et al., 2019). The risk is further compounded by the stationary nature of pole anchoring, which limits gear mobility and escapement opportunities during tidal shifts.



Catch composition of dominant fish species
 
The study documented 91 species from 44 families and 19 orders in dolnet fisheries at Karanja, Raigad, Maharashtra (Fig 3). Harpadon nehereus (64%) dominated catches, followed by Coilia dussumieri (13%) and Trichiurus lepturus (2%), indicating strong selectivity toward small pelagics. Similar dominance of H. nehereus and C. dussumieri was reported from Bhayander estuary in Thane district by (Pradhan et al., 2019)  though their catches included more estuarine species like Mystus gulio, Acetes indicus and Charybdis callianassa.


       
Seasonally, post-monsoon showed highest diversity (41 species), while monsoon (34 species) featured demersals like Saurida tumbil and crustaceans such as Acetes indicus. Pre-monsoon catches (38 species) notably included H. nehereus, Thryssa mystax and Pampus argenteus. Cephalopods (Uroteuthis duvaucelii, Octopus vulgaris) primarily occurred during pre and post-monsoon.
       
H. nehereus contributed approximately 580 kg/boat annually, adapting well to local estuarine conditions with seasonal surges (CMFRI, 2020). C. dussumieri ranked second in biomass while Acetes indicus showed consistent catches 90-100 kg/boat annually (Larsen et al., 2018; Pradhan et al., 2019). Other species like T. lepturus, Pseudosciaena diacanthus, Arius maculatus, Mystus gulio, Solenocera crassicornis, Decapterus russelli individually yielded less than 20 kg/boat. Ilisha filigera was negligible indicating possible rarity or fishing avoidance.
       
At Navabunder in Gujarat, Bombay duck dominated catches (69 to 77%) in 1986 followed by Coilia dussumieri, ribbonfish and non-penaeid prawns (Khan, 1986), whereas by 2018 non-penaeid shrimps led (40.22%) with Bombay duck and ribbonfish each at 15% (Sikotaria et al., 2018). At Navedar in Navgaon, Raigad district were ribbonfish (31%), Bombay duck (25%) and Indian cod (25%) were major species (Sehara and Kharbari, 1987). Madh Island catches were dominated by prawns (53%), while Navabunder showed seasonal dominance shifts, with Bombay duck in post monsoon and ribbonfish in pre monsoon. Sassoon Dock catches primarily included Harpadon nehereus (34.67%), Acetes indicus (32.09%) and Palaemon tenuipes (8.78%) (Pillai, 1983). These variations highlight adaptability and seasonal targeting influenced by regional ecology and fishing practices.
 
Seasonal catch comparison of major species
 
Harpadon nehereus dominated all seasons, peaking post monsoon, indicating significant recruitment or migration similar to findings by (Sreekrishna and Shenoy, 2001). Conversely, (Pradhan et al., 2019)  noted seasonal absence in Bhayander estuary, suggesting local variability. Coilia dussumieri showed highest catches pre monsoon, likely related to breeding or estuarine salinity shifts, declining thereafter. Acetes indicus exhibited stable catches year-round, reflecting environmental resilience. Other species (Trichiurus lepturus, Pseudosciaena diacanthus, Arius maculatus, Mystus gulio, Solenocera crassicornis, Decapterus russelli) had minimal contributions, primarily post monsoon, possibly due to spawning or improved gear performance. Ilisha filigera remained rare, suggesting limited abundance or gear avoidance. These patterns underline the need for season specific fishery management (Fig 4).



Order wise catch composition
 
Average monthly catch composition (Fig 5) revealed distinct patterns linked to species behaviour, habitat preference and gear selectivity. Aulopiformes dominated the catch, with the highest average contribution of approximately 2.7 kg boat^-1 day^-1, indicating its major role in the overall dolnet landings. This was followed by Acanthuriformes, which contributed about 2.0 kg boat^-1 day^-1. Moderate catches ranging from 1.5 to 1.8 kg boat^-1 day^-1 were recorded for Decapoda, Clupeiformes, Stomatopoda, Anguilliformes, Scombriformes, Perciformes, Crabs and Orectolobiformes, suggesting their regular availability in the fishing grounds. Intermediate catch contributions of 1.2 to 1.4 kg boat^-1 day^-1 from Carcharhiniformes, Cypriniformes, Myopsida, Gobiiformes, Siluriformes, Tetraodontiformes and Scorpaeniformes reflected occasional but consistent representation in the catch. Lower catches of about 1.0 kg boat^-1 day^-1 were observed for Beloniformes, Gadiformes and Pleuronectiformes, indicating relatively limited contribution compared with the dominant groups. The least abundant orders were Octopoda and Squamata, with average catches of approximately 0.5 and 0.2 kg boat^-1 day^-1, respectively, suggesting rare or seasonal occurrence (Pradhan et al., 2019). These variations highlight the influence of ecological availability and dolnet selectivity on catch composition, emphasizing the importance of order-level monitoring for assessing fisheries sustainability.


 
Species wise CPUE from dolnet trials at Karanja
 
Harpadon nehereus dominated catches (~565 kg/boat), followed by Coilia dussumieri (120 kg) and Acetes indicus (90 kg). Remaining species each contributed <10 kg, highlighting strong gear selectivity and fishery dependence on H. nehereus, emphasizing the need for targeted management (Fig 6).


 
Monthly catch and CPUE trends
 
Highest catches occurred in October (531,300 kg), aligning with post-monsoon peak fishing activity (Deshmukh, 2013). CPUE was highest in September (88.4 kg) and October (92.4 kg), while lowest in February (14.8 kg) and March (19.4 kg), consistent with (Khan, 1987) from Gujarat, albeit with higher CPUE values there due to fishing grounds and fleet size variations (Fig 7 and 8). Fig 9 provides additional comparative insights into temporal CPUE variations along Maharashtra coast, highlighting similarities in seasonal patterns with other regions.






 
Tidal amplitude influence
 
Catch rates correlated strongly (r=0.84) with tidal amplitude, peaking in September (~87 kg/boat, tidal amplitude ~5.0 m) and lowest in March (~36 kg/boat, tidal amplitude ~2.5-2.6 m). Enhanced catches during higher tidal amplitudes likely result from increased fish aggregation and improved gear performance (Soliman and Yamaoka, 2010)  (Fig 10 and 11).




 
Juvenile percentage composition
 
Juvenile bycatch peaked in September (21.3%) and August (20.4%), corresponding to recruitment phases for H. nehereus and C. dussumieri. High juvenile catch highlights urgent need for gear selectivity improvements. Square mesh codends (≥40 mm) could significantly reduce juvenile bycatch, aligning with sustainable fishing practices (Robertson and Stewart, 1988). The adoption of a 40 mm mesh size in dolnet fisheries targeting Bombay duck is supported by both biological and modelling evidence. The species has a minimum legal size (MLS) of 180 mm and a length at first maturity (Lm) of about 207-244 mm, so gear should achieve an L50 at or above these thresholds. Covered codend selectivity models allow testing of mesh sizes and results from earlier studies show that 30-40 mm codends improve mean size at capture compared with finer meshes. A 40 mm square mesh is the smallest size likely to reduce juvenile catch by 20-30% while keeping legal catch losses within 10%, thus aligning with MLS regulations and moving retention closer to Lm. Supporting tools such as bioeconomic yield-per-recruit analysis, morphometric escape tests and field trials further strengthen this recommendation.
 
Limitations
 
Dolnet operations are highly sensitive to environmental variability such as tidal currents, wind, depth and turbidity and even minor fluctuations can alter net geometry and escapement, complicating the assessment of gear effects. Although hauls were conducted across seasons, the spatial and temporal coverage may not fully represent all dolnet sites along Maharashtra’s 877.97 km coastline, as site-specific ecology and fisher practices influence catches. Juvenile classification relied on minimum legal size (MLS) or length at first maturity (Lm), but limited species-specific MLS data and uneven sample sizes, particularly for rarer species, introduce uncertainty. Complete gear standardization was not possible due to variations in dimensions, mesh size and anchoring methods among operators, with vessel and crew differences further adding variability. Finally, statistical analyses assume consistent data quality, yet outliers from weather, mechanical issues, or unusual species aggregations may affect outcomes and observed correlations (e.g., tidal amplitude and catch rates) cannot be interpreted as causation.
 
Implications
 
The study highlights the need for stricter enforcement of minimum legal size (MLS) regulations, particularly for Bombay duck (Harpadon nehereus) and supports incorporating gear modifications such as square mesh and double codends to curb recruitment overfishing. Improved selectivity can sustain fish stocks and ensure stable livelihoods for coastal communities by reducing juvenile mortality and preserving future yields. Documented gear variations provide a foundation for designing eco-friendly, standardized dolnets that balance efficiency with bycatch reduction, while the reduction of juvenile bycatch also aids biodiversity conservation and strengthens ecosystem based fisheries management in line with SDG 14-Life Below Water.

The study documented significant seasonal and spatial variations in catch composition, CPUE and juvenile bycatch in dolnet fisheries of Raigad, Maharashtra. A total of 91 species were recorded, with Harpadon nehereus and Coilia dussumieri dominating catches, particularly during the post monsoon period. Catch trends were positively correlated with tidal amplitude, indicating a strong environmental influence on fishing efficiency. Juvenile bycatch exceeded 20% during August and September, suggesting low gear selectivity associated with fine mesh codends and fixed anchoring systems. Introduction of 40 mm square mesh codends is recommended to reduce juvenile retention and improve gear performance. The findings contribute to a better understanding of dolnet operations in coastal waters and highlight the need for design modifications to support sustainable exploitation of pelagic fishery resources. The study provides a scientific basis for developing improved gear configurations suited to regional hydrodynamic and biological conditions in dolnet fisheries.

Gratitude to the Director, ICAR-CIFT Cochin, Scientist-In-Charge Mumbai Research Centre, ICAR-CIFE Mumbai scientists, Fishing Technology Division (ICAR-CIFT Cochin), staff and Young Professionals of Mumbai Research Centre and Maharashtra fishermen for their invaluable cooperation and support.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.
 
Informed consent
 
Not applicable for this study.

The authors declare that there are no conflicts of interest regarding the publication of this article. No funding or sponsorship influenced the design of the study, data collection, analysis, decision to publish or preparation of the manuscript.