Tuning and Development of an Individual-Based Model of the Herring Spawning Migration

Norwegian spring spawning herring is a migratory pelagic fish stock that seasonally navigates between distant locations in the Norwegian Sea. The spawning migration takes place between late winter and early spring. In this article, we present an individual-based model that simulated the spawning migration, which was tuned and validated against observation data. Individuals were modelled on a continuous grid coupled to a physical oceanographic model. We explore the development of individual model states in relation to local environmental conditions and predict the distribution and abundance of individuals in the Norwegian Sea for selected years (2015–2020). Individuals moved position mainly according to the prevailing coastal current. A tuning procedure was used to minimize the deviations between model and survey estimates at specific time stamps. Furthermore, 4 separate scenarios were simulated to ascertain the sensitivity of the model to initial conditions. Subsequently, one scenario was evaluated and compared with catch data in 5 day periods within the model time frame. Agreement between model and catch data varies throughout the season and between years. Regardless, emergent properties of the migration are identifiable that match observations, particularly migration trajectories that run perpendicular to deep bathymetry and counter the prevailing current. The model developed is efficient to implement and can be extended to generate multiple realizations of the migration path. This model, in combination with various sources of fisheries-dependent data, can be applied to improve real-time estimates of fish distributions.

Data-Limited Stock Assessment for Fish Species Devoid of Catch Statistics: Case Studies for Pampus argenteus and Setipinna taty in the Bohai and Yellow Seas

For many fish stocks, such as Pampus argenteus and Setipinna taty in China, size composition data are more accessible than catch data. Varied results can arise when different length-based stock assessment models are applied to these data, and fishery managers often need to reconcile conflicting estimates of population status. Superensemble modeling, a relatively recent innovation in fish stock assessments commonly used in other fields, may provide an effective solution to resolving uncertainties among the results from multiple length-based models. To verify potential for this approach to improve estimates of population status, we applied ensemble modeling to fit simulated data of P. argenteus and S. taty in the Bohai and Yellow Seas using predictions from a length-based integrated mixed effects (LIME) and length-based spawning potential ratio (LB-SPR) models as covariables in a superensemble model developed in this study. All simulation modeling of P. argenteus and S. taty in the Bohai and Yellow Seas was conducted using the operating model in the R package LIME. Initially, the LIME and LB-SPR performances were tested separately under three scenarios of fishing mortality and recruitment variability (“equilibrium scenario,” “endogenous scenario,” and “one-way base scenario”). Then, estimates of spawning potential ratio (SPR) were combined with the superensemble models (a linear model, a support vector machines, a random forest and a boosted regression tree). We trained our superensemble models with 80% of the simulated data and tested them with the remaining 20%. Our results showed that superensemble modeling substantially improved the estimates of SPR, with support vector machines performing the best at estimating population status: precision improved by 12.7% for S. taty and 8% for P. argenteus on average (namely, median absolute proportional error decreased by 0.127 and 0.08 on average) compared to the individual models. This finding has important implications for fisheries management in the context of species for which catch data are unavailable. Applying the size composition survey data, the results from support vector machines superensemble model suggested that neither S. taty nor P. argenteus in the Bohai Sea in 2019 are overfished, but the stock status of P. argenteus warrants vigilant monitoring.

Catch Composition of Set Net Fisheries during Normal Season in Sungai Sembilang Waters, Selangor, Malaysia

Highlight ResearchThe Set Net was identified and recorded.Length and weight of the catch of set net was analyzed. AbstractSet net fisheries are made according to traditional fishing gears method in the coastal waters of Sungai Sembilang, Selangor, Peninsular Malaysia. These fisheries system are the passive structure of gear used to catch fish that swim in shallow water with muddy substrate. This study focused on determining the species variety and the possible future of set net fisheries in Sungai Sembilang. Catch composition of set net was investigated based on the catch data during July to December 2020 and continued from January to February 2021. The catch data was recorded by a research assistant on site during fishing season. The data consist of species, length and weight of all catches recorded. Total catch of 60 fish species belonging to 23 families were captured during this study period. Ariidae (31.73%), Clupeidae (11.56%), and Scatophagidae (7.96%) were determined as dominant families caught this set net. The total dominant catch amount of species Plicofollis argyropleuron (18.71%), Nemapteryx caelata (9.96%), and Anodontostoma chacunda (8.92%) compromised 37.6% of the total catch. This type of fishing gear can be used by local fisherman to catch fishes and can prevent trawl net from come closer to the shore. This study would provide some general useful information about the status of set net fisheries as well as the species abundance caught from the set net.

The Biology of Mesopelagic Fishes and Their Catches (1950–2018) by Commercial and Experimental Fisheries

Following a brief review of their biology, this contribution is an attempt to provide a global overview of the catches of mesopelagic fishes (of which 2.68 million tonnes were officially reported to the FAO) throughout the world ocean from 1950 to 2018, to serve as a baseline to a future development of these fisheries. The overview is based on a thorough scanning of the literature dealing with commercial or experimental fisheries for mesopelagics and their catches, and/or the mesopelagic bycatch of other fisheries. All commercial (industrial and artisanal) fisheries for mesopelagic fishes were included, as well as experimental fisheries of which we were aware, while catches performed only to obtain scientific samples were omitted. The processes of generating bycatch and causing discards are discussed, with emphasis on Russian fisheries. From peer-reviewed and gray literature, we lifted information on mesopelagic fisheries and assembled it into one document, which we then summarized into two text tables with catch data, one by country/region, the other by species or species groups.

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.