Swept Area Method Research Articles

Size‐based indicators of unexploited deep‐sea community in the Colombian Caribbean Sea

AbstractComposition, size distribution, structure, and function of deep‐sea marine communities must be understood before they are impacted by anthropogenic effects. The deep‐sea ecosystem of the Colombian Caribbean Sea is unexploited with no fishing activity ever registered. We quantified the current state of the marine community using body size distribution (size‐spectra), size‐based indicators, minimum length (LMIN), maximum length (LMAX), average length (Lmean), standard deviation of length (LSD), 10th and 90th percentiles of the length distribution, Shannon–Wiener diversity (H′), and Pielou's evenness (J′) to generate a baseline of potential ecological indicators that contribute to management and conservation of the Colombian bento‐demersal community of deep‐sea marine ecosystem. Sampling was in the Colombian Caribbean Sea at 58 stations during four samplings in August and December 2009, 21 stations in March and May 2010, and 45 stations from August to December 2020, using the swept area method, at depths of 200–550 m. Catches included >50% families and species of fish, followed by 27 families (30%) and 33 and species (37%) of crustaceans. Chondrichthyes included 14% families and 9–11% species. Cephalopods included 2–3% families and 1–4% species. Size‐spectra analysis confirmed expected values for unexploited communities in three sampling years for teleostei, crustacea, and whole community.

Azov sea fishes stock assessment by swept area method through bootstrap

Recently driven changes in habitat conditions in the Azov Sea make classic applications of swept area method inconsistent. Swept area stock assessment method modification for stock estimation of aquatic biological resources through nonparametric bootstrap is presented. New approach is tested against classic calculated results of swept area method for next fish species: Azov anchovy, tulka, turbot and Black-Azov sea shad according to data collected during 2022. Results comparison of classic and modified through bootstrap stock assessment methods leads no significant deviations in mean value estimation. Maximum difference between mean estimates of stock size was 3,75%. Confidential intervals width difference between reviewed methods, in general, was not significant. Most valuable difference in confidential intervals was detected in BCa approach against classic method with quantile approach (due to methodological features of BCa in bias correction procedure). The new stock assessment approach for swept area method though bootstrap permit to calculate statistically valid estimates, their confidential intervals and perform input data validation. The absence of significant differences in the results by the classical and proposed methods indicates the further applicable possibility of classic method even in normality violation in source samples. The normality requirements in methodology of classic approach, probably, is redundant.

Relationships between Fish Community Structure and Environmental Factors in the Nearshore Waters of Hainan Island, South China

The nearshore ecosystem of Hainan Island plays a crucial role as a breeding habitat for a wide variety of economically valuable fish species. Gaining insight into the structure of the fish community and the environmental factors that may impact them is highly significant in this marine region. This study collected fish data from 50 sampling sites using bottom trawling surveys. Methods including the swept area method, ecological indices, and abundance/biomass curve (ABC) analysis were employed to assess fish resource density and diversity. A comprehensive identification revealed a total of 363 fish species, encompassing 24 orders, 114 families, and 226 genera, with Perciformes being the dominant group. Spring exhibited higher fish abundance and biomass compared with autumn, with the southwestern waters as the primary concentration area. Acropoma japonicum, Decapterus maruadsi, and Navodon xanthopterus were dominant in spring, while Leiognathus bindus, Saurida tumbil, and Champsodon atridorsalis were dominant in autumn, indicating a seasonal shift towards smaller and lower-value fish species. A variability exceeding 80% was observed through SIMPER analysis, and a disrupted community structure was evident in the eastern and southern waters. Temperature and salinity were identified as primary environmental factors influencing the fish community. Overall, this study provides valuable insights into the nearshore fish community of Hainan Island, aiding in the understanding of its structure and dynamics.

First descriptions of diurnal pelagic aggregations of the Argentine red shrimp (Pleoticus muelleri) using a broadband echosounder operating at multiple frequencies

This is the first description of diurnal pelagic aggregations of the bottom-dwelling Argentine red shrimp (Pleoticus muelleri) registered with a broadband scientific echosounder. A pelagic trawl net and an underwater video camera were used to validate all the information presented in this paper. Shrimp aggregations were characterized by increasing frequency response, more evident at frequencies greater than 120 kHz. Identification of the acoustic signature of this resource is of particular interest for the development of new methodologies to complement the traditional swept area method of estimation.

Abundance and distribution of subsurface microfibres and seabed macrolitter in Thoothukudi, Gulf of Mannar, South-east coast of India

Aim: Considering the potential harm caused by plastic pollution to the marine ecosystem, the present study was conducted to elucidate the status of microfiber and macrolitter in the selected areas of Thoothukudi on the South-east coast of India. Methodology: The abundance and distribution of subsurface microfibers in four locations of Tuticorin inshore waters were estimated by filtering subsurface waters using a 250µm mesh epineuston net. The non-biodegradable macrolitter on the seabed at three locations of Thoothukudi was estimated by swept area method. Results: Among the four selected stations, a higher quantity of microfibres was observed in the subsurface waters at 5m depth close to nearshore areas, with the highest mean numerical abundance of 3.13±0.3 nos.m l-1. The annual difference in the subsurface microfibre abundance varied significantly between stations (p<0.05). Plastics were the most dominant litter constituents on the sea beds among three stations. A significant seasonal variation (p<0.05) with maximum mean total macrolitter abundance was noticed on the seabed at Kayalpattinam (45.81± 9.3 kg km-2). The estimated mean macrolitter abundance at all the stations was higher than the reported national average of 10.95±3.05 kg km-2. Interpretation: This study revealed variations in the abundance and distribution of microfibers and macrolitters in the selected areas of Tuticorin. The study emphasises the role of land and marine-based anthropogenic activities in the plastic pollution of this region. Key words: Abundance, Gulf of mannar, Microfibres, Macrolitter, Subsurface waters, Seabed

Shrimps distribution and their relationship to the environmental variables in Arafura Sea

Arafura Sea is well-known as the important area for commercial shrimp fisheries in Indonesia. The density of shrimps was highly influenced by their fishing pressure and environmental condition. The objective of this research was to study the distribution of shrimps based on its stock density and their relationship with the environmental variables. Trawling swept area method was used in 16 sampling sites of Arafura Sea during the transition monsoon in 2016. Some environmental variables in bottom layers as shrimp habitat were measured, including chlorophyll-a, dissolved oxygen, depth, salinity, temperature and pH. The results showed that the largest density of shrimps was found in the southern coast of Aru where it has the largest concentration of chlorophyll-a and dissolved oxygen. Among all the environmental variables, Chlorophyll-a was the main variable affected the density of shrimps. Three most dominant species were Penaeus semisulcatus, Metapenaeus endeavouri and Metapenaeus ensis. There was indication of the decreasing shrimp stock in Arafura Sea. The ecosystem-based fisheries management should be developed to rebuild the stock density and to enhance the environmental quality of Arafura Sea.

Designing and the Pilot Trial of Bivalve Molluscan Fishing Quotas on Maoming Coastal Waters of China, Northern South China Sea

In the context of the declining fishery resources, some active management measures have been taken to strive for the sustainable development of fisheries. However, these input-oriented control management measures have not realized the expectation in alleviating the depressing depletion of fishery resources. The fishing quota (FQ) system, an output-oriented control management method, has been proved to be effective in curbing overfishing and conserving fishery resources. However, it has not been formally implemented in China until now. Thus, it is urgent to start the pilot trial on the implementation of the FQ system in China. We firstly formulated a framework for the FQ system on bivalve fisheries and then conducted an empirical analysis based on the field survey of bivalve mollusks in Maoming shallow waters, Guangdong, northern South China Sea. The species composition, dominant species, and density distribution of bivalves were analyzed. The swept-area method was used to assess the total allowable catch (TAC) of bivalves. Each step of the FQ system was discussed in depth. Results showed that a total of 45 bivalve species were identified. Meretrix planisulcata and Ruditapes philippinarum were the two dominant species. The spatial distribution of density varied largely. The estimated TAC value is 4.28 × 105 kg which can be allocated to fishermen under the regulations of the FQ system. Finally, the framework for the FQ system was improved in every step of the future procedure, including target species selection, TAC determination, quota allocation, catch report, and fishing supervision. The general framework of the FQ system in this study can also be referenced to other economically important fish or other marine organisms.

A matter of size: the population structure of the smallest known living shark, Etmopterus perryi (Springer & Burgess,1985), from deep waters off the Colombian Caribbean coast.

The dwarf lanternshark (Etmopterus perryi) is the smallest known described shark, and practically no information has been available on this species since first described in the mid-1980s. Therefore, the aim of this work is to describe, for the first time, the population structure regarding dwarf lanternshark in the Colombian Caribbean Sea. During deep-water research surveys conducted along the Colombian Caribbean coast, 87 stations were sampled using the swept area method. A total of 153 dwarf lanternshark individuals were caught in depths ranging from 230 to 530 m. This information was used to describe the size structures, morphological measurements including length-at-weight relationship, length at maturity in females and the spatial distribution of mean length and biomass of the species. The lengths of individuals ranged from 78.02 to 289.00 mm total length (TL), which is a new record of maximum length for this species. The spatial distribution of mean lengths and biomass distributions show high abundances and high relative mean lengths in the northeast area off Santa Marta and the area northwest of Riohacha. The mean biomass density in the whole prospected area was 5.52 kg km-2 . Length at 50% maturity in females was estimated in 203 mm TL (95% C.I.: 190-214 mm). Deep-water elasmobranch species, such as the dwarf lantern shark, are expected to show extremely low resilience to fishing exploitation, even when they are not targeted by commercial fishing. Therefore, the information reported in this study can serve as a baseline upon which management measurements can be proposed for the conservation of this shark species.

Production and Biomass of Pokea Clam (Batissa violacea var. celebensis von Martens, 1897) in the Langkumbe River Waters North Buton Southeast Sulawesi

Langkumbe River is located in West Kulisusu District and has long been used by the community for various daily activities. One of the resources often used by the people around Langkumbe River is pokea clams. The aim of this study was to determine the production and biomass of pokea clams (B. violacea) in Langkumbe River Waters of North Buton Regency from August to October 2017. The sampling method used was swept area method using a traditional fishing gear "Tangge" (fishing gear). The samples were measured for the length, width and thickness. The total weight was measured with the clam/total mass (MT) and the weight of the meat. The samples were dried using an oven for 24 hours at 70 °C to obtain the shell-free dry mass (SFDW). Data were analyzed using standard formulas. The total sample obtained was 1.307 individuals. The highest density of pokea clam was found in August at 596.8 ind/m². Annual production of pokea clam (B. violacea) in Langkumbe River with a total annual production of 1,107.33 gSFDW/m2/year. The highest and lowest production are 297.09 gSFDW/m²/year at size 2.19-2.54cm and -0.16 gSFDW /m²/year at size 4.70-5.05cm, respectively. The total population biomass was 528.03 gSFDW/m2 with the highest biomass 171.72 gSFDW/m²/year at size 2.55-2.90 cm and the lowest was 1.40 gSFDW /m²/year at size 4.70-5.05 cm, so that the recovery rate (P/B ratio) was 2.1 gSFDW/m2/year.

Population Aspects of Graceful Mojarra Eucinostomus gracilis (Perciformes: Gerreidae) in a Coastal Lagoon in the Tropical Eastern Pacific

Graceful mojarra (Eucinostomus gracilis) is an important component of the ichthyic fauna of lagoon systems but knowledge of its population aspects is scarce. Monthly samples in the Magdalena-Almejas Lagoon system (March-August, 2014-2017) were obtained with a trawling net. Abundance was estimated using the swept area method and its spatial variation; and the maturity size was determined using the logistic method. The sex ratio for mature and immature populations, and their length-weight relationship were estimated; FISAT was used to estimate the growth and recruitment parameters. Abundance ranged from 0.6 to 203 ind-Ha-1 with changes for each lagoon system areas and among years. Size at maturity (L50) was 132 mm in total length (TL) for the population, 129 mm TL females, and 135 mm TL males. Considering the population of the total organisms, L50 indicated that 18% were adults and 82% were juveniles. Juvenile dominance indicated that this lagoon system is used for grow-out. The smaller ratio of adult organisms does not allow asserting assertion that the priority of the area is for reproduction. E. gracilis showed moderate growth (K = 0.56 year-1) with longevity of 5.4 years and asymptotic length of L∞ = 195 mm.

Comparison of biomass estimates from multiple stratification approaches in a swept area method for Pacific saury Cololabis saira in the western North Pacific

Fishery-independent surveys using sea surface trawl nets for Pacific saury Cololabis saira in the western North Pacific since 2003 have enabled the investigation of their annual distribution patterns and total biomass during June and July, prior to the main fishing season in Japan. We compared biomass estimates and their associated variances derived based on five different post-stratification approaches in a swept area method, and then observed that these approaches have little effect on biomass estimates and their precision, owing to well-organized survey designs and homogeneously allocated sampling stations. We were able to utilize decreasing biomass estimates for 15 years as an essential abundance index in the ongoing stock assessment. Notably, examination based on stratification along with longitudinal survey lines indicated that the estimated biomass had decreased in the western survey area, resulting in an eastward shift in the gravity center of Pacific saury distribution after 2010. We recommend biomass estimation in an east–west direction based on longitudinal stratification as an effective measure to develop population dynamics models which reflect westward migration into the fishing grounds around Japanese coastal waters, and to forecast the expected catch during the subsequent fishing period.

Biodiversity and biomass of bentho-demersal megafaunal assemblages of the yellow and red squat lobster fishing grounds in Central Chile (Eastern Pacific Ocean)

Biodiversity and biomass patterns of megafaunal assemblages were assessed from the yellow (Cervimunida johni) and red (Pleuroncodes monodon) squat lobster fishing grounds in the Southeastern Pacific Ocean during four years. Bottom trawls were conducted applying the swept-area method in a stratified sampling design, obtaining global and specific catch per unit area (CPUA). We recorded two target and 47 by-catch species, with a total CPUA of 80.000 t/km2 (cumulative from 2005 to 2008) Fishes and crustaceans dominated over other taxonomic groups. Classes Actinopterygii and Malacostraca attained the highest specific richness; the presence of a few dominant and many rare species in terms of CPUA and frequency, was characteristic of the studied assemblages, hence, the general CPUA pattern parallels that of the most abundant species in the bathymetric and latitudinal gradients. The three most conspicuous non-target species, Heterocarpus reedi, Merluccius gayi gayi and Hippoglossina macrops accounted for 91% of the by-catch CPUA, whereas Class Malacostraca also represented 91% of the total CPUA. The highest average specific richness occurred at intermediate depths (300–400 m) and the lowest in shallow waters (50–100m); the highest overall CPUA occurred at 100–200m and the lowest at both 400–600m and 50–100m. Depth was the most significant factor in the variability of our assemblages. However, particular features of the Humboldt Current System might act as drivers of important effects across the latitudinal gradient on the high productivity and dynamism of the squat lobster fishery, despite the homogeneous composition of the community. This study shows the importance of considering the whole biodiversity within appropriate management actions, in order to achieve ecological benefits (e.g. resilience, functional diversity, water quality, primary productivity) in communities subjected to fishing pressure.

Biomass and distribution of the red octopus (Octopus maya) in the north-east of the Campeche Bank

AbstractThe regulatory framework of the red octopus (Octopus maya) fishery includes total allowable catches (TAC), which are based on studies conducted on the population that occurs in shallow waters. In fact, most of the biological studies of this species refer to the fraction of the population that occupies waters less than 30 m deep; however,O. mayacan occur up to a 60 m depth. The aim of this study is to assess the stock ofO. mayathat occupies waters between 30 m and 60 m deep. Four research cruises were carried out during the closed and fishing seasons, from May 2016 to January 2017. An average of 29 sampling sites were surveyed in each cruise (±2 sampling sites) using a commercial vessel with a uniform sampling effort. In each sampling site, the swept area, the total number of octopuses captured, the total weight of the catch, and the individual weight of octopuses were recorded. Biomass was obtained with four methods: stratified random method, swept area method, geostatistical biomass model, and an unpublished method of weighted swept area. The four methods provided consistent results. The distribution pattern of species was in patches, although before the fishing season started it was more homogeneous. The fraction of the population that occurs between 30 m and 60 m deep consisted mostly of adult organisms, so it could be contributing significantly to the recruitment of the entire population, even to the fraction that is exploited.

The biomass, abundance, and distribution pattern of starfish Asterias sp. (Echinodermata: Asteroidea) in East Coast of Surabaya

This study aims to determine the biomass, density, and distribution patterns of Asterias sp. Samples were collected from three locations such as Wonokromo, Dadapan and Juanda, each divided into 3 zones. In each zone, samples were taken as many as 5 repetitions using swept area method. Temporarily, the highest biomass of starfish was 2.95 gr/m2 in Dadapan Zone on January. Spatially, biomass of starfish was found in Dadapan Zone (3,35 gr/m2). Similarly, the high density was also found in Dadapan Zone on January (9 ind/10 m2). In general, the distributionpattern of starfish in East Coast Surabaya throughspatial and temporal showed that the pattern of starfish was grouping distribution (Id value > 1) for Dadapan and Juanda, and uniform for Wonokromo. Oceanographic condition, antropogenic activity, and water quality in East Cost of Surabaya become important things which is affected the biomass, densityand distribution pattern of starfish. The knowledge of starfish biomass and density is very important given that this biota has ecological value as a balancing ecosystem in the waters.

Effects of environmental variables on survey catch rates and distribution by size of shallow‐ and deep‐water Cape hakes, Merluccius capensis and Merluccius paradoxus off Namibia

AbstractIn order to study the effects of temperature, oxygen, salinity and time of day on survey trawl catches, we modeled observed catches of juvenile, small, medium and large hakes per station as functions of zenith angle of the sun, geographical position, year, temperature, salinity, oxygen and depth. We used data from summer demersal surveys conducted during the period 2002–2015, together with a computation of the corresponding light level data from which the solar zenith angles were obtained, and fitted the generalized additive models to these data. Based on best model results, important covariates were oxygen, depth, geographical position and temperature. The best models explained 70%, 69%, 57% and 57% of the variability in catches of juvenile, small, medium and large Merluccius capensis, respectively, and 71%, 68%, 81% and 70% of juvenile, small, medium and large Merluccius paradoxus, respectively. The significant effects of temperature, oxygen, depth and geographical position on survey catches of hake of different size groups indicate that survey size structure may be affected by the behavior of both species towards environmental conditions. Greater care should therefore be taken when interpreting hake survey biomass estimates, based on swept area method, especially those that were collected during exceptional unfavourable environmental conditions. It would also be highly desirable if the oceanographic conditions are collected on each trawl station in order to improve understanding of the linkage between resources and environmental conditions.

Stock assessment of juvenile sturgeons in the Iranian water of the Caspian Sea by bottom trawl survey

The sturgeon stock assessment was performed to aim at estimation of absolute and relative abundance and determination of species composition at lower 10 m depths using the Si-Sara2 RV vessel in the Iranian coasts of the Caspian Sea in Guilan, Mazandaran and Golestan provinces during 6-30 September 2011-2012. In this study, 40 stations were selected on the basis of stratified random sampling design and then the stock estimation was performed using the swept area method. The study was carried out using bottom trawling with 9 m head rope. The time and speed of trawling in each station were 30 minutes and 2.5 knots respectively. The Catch per Unit of Effort (CPUE) in 2011–2012 were 7.03 and 6.96 individuals per trawling, respectively. The catch per unit of area in these years were found to be 1662 and 1644 fish in nm2, respectively. Total abundance of sturgeon juveniles was 13,327,164 individuals in 2011. So, the species composition included A. persicus (87.8%) and A. stellatus (12.2%). Total abundance of sturgeon juveniles was found to be 14,364,882 individuals in 2012 and the species composition comprised A. persicus (61.4%) and A. stellatus (38.6%). In 2011 the biomass of sturgeons in Iranian coastal water of the Caspian Sea was 295 tons and the composition of biomass included A. persicus (81.5%) and A. stellatus (18.5%), respectively. In the cruises conducted in 2011, this amount was estimated to be 217 tons comprising A. persicus (54.2%) and A. stellatus (45.8%), respectively. The results of this study in 2011–2012 showed remarkable abundance of juvenile sturgeons in Iranian coastal waters of the Caspian Sea in late summer and early autumn. So, by conserving these valuable stocks, the number of spawners will be increased in the future.

SPECIES COMPOSITION, DISTRIBUTION, AND POTENTIAL YIELD OF DEEP SEA SHRIMP RESOURCES IN THE WESTERN SUMATERA OF THE INDIAN OCEAN EEZ OF INDONESIAN WATERS

study on the catch composition, distribution and potential yield of deep sea shrimp in the westem off sumarera waters was conducled on June to July 2005 using RV Baruna Jaya lV with trawl net. This study was basicarry caffied out by emproying swept area method

POTENTIAL YIELD OF DEEP SEA SHRIMP RESOURCES IN THE SOUTHERN JAVA OF THE INDIAN OCEAN EEZ WATERS

Study on the potential yield of deep sea shrimp in the south off Java waters (lndian Ocean) was carried out based on data collected from the survey conducted between May and June 2005 using Baruna Jaya IV research vessel. This study was basically conducted by applying swept area method.

Characteristics of Beach Seine Fishery of East Java: Facing Ministerial Decree of Marine Affairs and Fisheries No. 2/2015

Catch biomass and time-trend perception of Beach seine fishery were studied during 2015, from four different sites in East Java: Padikde Madura, Santan Island Banyuwangi, Prigi Beach Trenggalek, and Dangkal Beach Pacitan. The study aimed to assess the impact of recently Ministerial Decree (No. 2/2015) on this particular fishery. Catch biomass was analyzed based on swept area method. Time trend perception was traced back from fishermen in relation to reduced catch biomass, catch size, habitat degradation, and income contribution from the fishery. The results showed that Beach Seines in East Java are considerably subsistence. It swept fixed-bottom habitats of 1–9 ha. Average catch biomass for all sites was 15±19.4 kg trip -1 . With low price of fish catch, fishermen cannot place down their family income solely from this livelihood. Beach seine is more as to maintain tradition of subsistence. Fishermen clearly observed the reduced in catch biomass and catch size compared to what it used to be (±30 years ago). With very low contribution to total catch in the region, negligible impact to habitat degradation, and consumed no fuel subsidy, it is no real reason to include this gear in general ban through Ministerial Decree of Marine Affairs and Fisheries.

SPATIAL AND TEMPORAL VARIABILITY OF FISH COMMUNITY BIOMASS IN COASTAL WATERS OF TANGERANG REGENCY, BANTEN

Coastal waters of Tangerang Regency has abundant in fish resource including pelagic, demersal, and reef fish. This study was conducted to assess fish biomass variability and of fish community structure in coastal waters of Tangerang Regency which can be used as a basis in determining alternatives for sustainable fish resource management. This research was conducted in June and August 2013 in three locations i.e., Kronjo, Cituis, and Tanjung Pasir. Primary data collected were fish weight per species. Fish biomass from each locations was obtained using swept area method using trawl. The results showed that Kronjo region contained the highest total average biomass of fish. Temporally, total ave-rage biomass of fish in August was higher than in June for Kronjo and Cituis. Meanwhile, the con-trary occurred in Tanjung Pasir. This conditions occurred due to the high current and high wave in August than in June. In general, biomass of planktivorous was dominant during the study indicating overfishing lead to fishing down the food web in the Coastal waters of Tangerang Regency. Keywords: biomass, coastal waters of Tangerang Regency, spatial and temporal variability, swept area, over fishing.