Fish Population dynamics, stock assessment and Fisheries management

Population dynamics of Upeneus sulphureus in the Visayan Sea was assessed using the FiSAT
II program from a sample collected by trawl fishing from November 2018 to October 2019. A total of
1,129 individuals with lengths ranging from 8.0 to 18.5 cm were included in this study. The asymptotic
total length (L∞) was 20.63 cm, and the growth constant (K) was 1.4 year-1, revealing that this is a fast-
growing species. The mean length was 13.35 cm with a growth performance index (φ) of 2.78. The total
mortality rate (Z) was computed as 5.34 year-1, the natural mortality rate (M) was 2.47 year-1, and the
fishing mortality rate (F) was 2.87 year -1. The quotient of F/Z values computed an exploitation ratio (E)
of 0.54. The obtained E exceeded the 0.5 threshold, which indicates the presence of growth overfishing.
The ideal management interventions for this species are to increase the mesh size of nets and decrease
effort levels to allow sustainable exploitation of the stock. These measures should be implemented to
ensure continuous food protein supply and income of the fisherfolk who rely on the Visayan Sea fishery.

Keywords: Growth parameters, Mortality rates, Sulphur goatfish, Visayan Sea

Ikan lemuru (Sardinella lemuru Bleeker, 1853) berperan penting dilihat dari sisi ekologi dan ekonomi. Tingginya permintaan pasar terhadap ikan lemuru mengakibatkan aktivitas penangkapannya dilakukan secara terus-menerus sepanjang tahun sehingga mengancam kelestariannya. Namun, ketersediaan data yang terbatas menjadi penghambat dalam upaya mengevaluasi status pemanfaatan stok, khususnya untuk kegiatan perikanan skala kecil. Penelitian ini bertujuan untuk mengetahui status stok sumberdaya ikan lemuru di perairan Selat Bali yang dilakukan dari Agustus 2010 hingga Desember 2011. Pengkajian stok ikan lemuru dilakukan dengan pendekatan ratio potensi pemijahan yang berbasis ukuran panjang. Studi literatur juga dilakukan untuk mendapatkan parameter-parameter life history sebagai pendukung analisis. Hasil penelitian menunjukkan bahwa status stok ikan lemuru telah mengalami eksploitasi berlebih (over exploited) yang diindikasikan dengan nilai Spawning Potential Ratio (SPR)<20%. Indikasi lainnya terjadinya over exploited adalah SL50<Lm dan F>M. Upaya pemulihan stok perlu dilakukan agar tercapainya SPR menjadi 20% dan 40% sebagai batas dan target biologi untuk keberlanjutan sumberdaya ikan lemuru.

This research was conducted from 9 until 20 October 2006 at Pelabuhanratu port. The research goal is to know the various fishing gear, trip, production, sustainable yield, utilization level of ribbon fish that were landed at Pelabuhanratu port and to know amount of fishing instrument at Pelabuhanratu. Statistic data were obtained from the port and analyzed by a surplus production models (Schaefer).  Fishing gear of ribbon fish were hand line, seine net, and lift net. Maximum sustainable yield (MSY) with three fishing gear are 318.7 tons and maximum effort (fopt) are 1,023,322 trips. Ribbon fish utilization level about 5.75% - 88.46% with average/year is 50.23% (growth). Effort level about 24.61% - 201.48% with average/year is 50.68% .

A major constraint to science-based fish stock management in West Africa is the lack of reliable data on target stocks. This especially holds true for inland fisheries, such as those that operate in reservoirs. Due to the low availability of resources and population data, and the limited number of fisheries experts in the region, state institutions and investigators rely heavily on simple catch statistics and empirical models for their estimations of fish production and potential yields. This paper reviews data from the FAO, and published articles and reports on West African reservoirs, with special reference to their morphome-tric and environmental features in relation to fish catch. In addition, we analyse primary data on three focus reservoirs. First, to improve and update available models of potential harvests from reservoirs, we regress fish catch data against reservoir surface area data for 30 reservoirs in West Africa, yielding the following equation: Catch (tonnes/year) = 17.3 × Area (km 2) 0.8626. The equation accounts for 95.7% of the variation observed in the fish catches. Analysis of covariance of small (< 2 km 2) and large (> 2 km 2) reservoirs shows no significant difference (F = 0.5895, p = 0.45) in the slopes of the two groups. Second, we apply multiple regressions to a sub dataset of 15 reservoirs with surface area and mean depth as predictors; and we also explore reservoir age as a further variable. We find that fisheries productivity is inversely correlated with both mean depth (r =-0.49) and surface area (r =-0.32), but there is no significant correlation found with reservoir age (r = 0.03).

Fish stocking (artificial supplementation) has been used to augment populations and angling opportunities. However, genetic composition and adaptations of native fish populations may be affected, raising management concerns. From 1995 to 2000, the New York State Department of Environmental Conservation stocked Walleye Sander vitreus fry and fingerlings from the Mau- mee River (western Lake Erie) into Cattaraugus Creek (eastern Lake Erie). We analyzed nuclear microsatellite (msat) DNA and mitochondrial DNA (mtDNA) variation in Cattaraugus Creek Walleyes for comparisons between prestocking and poststocking groups, among annual spawning runs (1998–2011), among age cohorts, and between sexes. Results for genetic differentiation (index FST) were not significant between prestocking and poststocking groups (msat: FST D 0.003; mtDNA: FST < 0.001), and the two groups did not resemble stocked Maumee River fin- gerlings (msat: FST D 0.003–0.012; mtDNA: FST D 0.076–0.090). Tests for differentiation were not significant among annual spawning runs (msat: FST D <0.001–0.007; mtDNA: FST D <0.001–0.049), among age cohorts (msat: FST D <0.001–0.006; mtDNA: FST D <0.001–0.097), or between sexes (msat: FST < 0.001; mtDNA: FST < 0.001). Genetic diversity levels were high and consistent (msat: observed heterozygosity [mean § SE] D 0.71 § 0.04; mtDNA: haplotype diversity D 0.79 § 0.01). Thus, despite stocking, the genetic signature of the native spawning run remained distinctive. However, the genetic composition of the local wild population and the stocking source should be assessed prior to any future supplementation plans.

The popular aquarium fish called damselfish are valuable because of their commercial and ecological value. As the demand for these fishes is increasing, their estimation techniques carry great significance. Most conventional techniques for biomass estimation are visual sampling techniques, raft and floating radio frequency identification (RFID) tag systems, minnow traps, removal method of population estimation, etc., which are complex and require human interaction. Moreover, the instruments and devices used in these techniques are costly. With the aim of overcoming these difficulties, a cross-correlation based signal processing approach is presented in this research in order to estimate damselfish biomass in the sea. The estimation process is based on the production of an acoustic signal (called “chirp signal”) of these fish species during swimming within their territory. To evaluate the performance of the estimation, three different distributions of damselfish are considered in this paper. However, the chief goal of this investigation is to establish a new model of biomass estimation that will benefit research and commercial fishery management.

Cross-correlation based fisheries stock assessment technique utilized array of multiple acoustic sensors which were equidistant pair. However, at practical implementation of this technique, equal distances among acoustic sensors is sometimes challenging due to different practical phenomenon. Therefore, in this study, we work on this issue and investigated the impact of unequal distances among the acoustic sensors. We found that cross-correlation based technique proved its effectiveness even for the unequal spacing among acoustic sensors. We considered chirp generating species of fish and mammals, i.e., damselfish (Dascyllus aruanus), humpback whales (Megaptera novaeangliae), dugongs (Dugong dugong), etc., species, and three acoustic sensors array for simulation purposes. Some limitations including negligence of multipath interference, assuming the delays to be integer were compromised during simulations. In worldwide, over 800 species of fish and mammals from 109 families are identified to be soniferous 1 , although this is likely to be an underestimate. Over 150 species of these are found in the northwest Atlantic 2. Amongst the soniferous fish and mammals, some of the most abundant and vital commercial species are codfish, drum fish, grunts, groupers, snappers, jacks, catfish 3 , hambuck wheals, dolphins, etc. Utilizing the sounds of fish and mammals is recognized as passive acoustics which has been used for over 50 years in fish biology and fisheries surveys 2. In fact, it is used routinely to delineate and monitor spawning areas, and study the behavior of fish and mammals 4,5. The researchers use hydrophone to listen this sound from fish and mammals to identify species 6,7 and estimate their population size 5. They use signal processing and spectral analysis computer algorithms to perform their tasks for this purpose 5,6. Generally, passive acoustic monitoring is a technique which is distinguished from other types of bioacoustics since it utilizes naturally occurring sounds to gather information on fish and mammals, rather than using artificially generated sounds. It offers a number of benefits to survey fishery population in a certain marine area including being a method of non-optically observing fish activity and distribution, being a non-invasive and non-destructive observational tool, providing the capability of continuous or long-term monitoring as well as remote monitoring, etc 6. In addition, investigators use passive acoustics to monitor the sources of noise pollution, and to study the impact of man's activities on marine communities 6. A straightforward, cross-correlation based population estimation technique was proposed in Refs. 8,9 , was a passive acoustic monitoring technique, can solve some major drawbacks of conventional fish population estimation techniques. Researchers investigated different practical impacts which were associated with this technique. Hossain and Hossen have investigated the impact of increasing number of acoustic sensors, i.e., increasing number of cross-correlation function (CCF) in Ref. 10. Hossain and Hossen also have shown the effect of underwater bandwidth and SNR on this technique in Ref. 11. Impact of dispersion coefficient on this technique was investigated in Ref. 12. Similarly, impact of different distribution on estimation was demonstrated in Ref. 13. Hossain and Hossen have investigated the procedure of calculating statistical error of this technique illustrated in Ref. 14. However, in the former researches, all the researchers have considered equal distance among the acoustic sensors. This is sometimes impossible in some practical cases because it is somewhat troublesome to put the sensors at the desired locations in the randomly distributed fish and mammals. So, the constraint of equal spacing among open sensors makes this technique difficult to implement practically, which is recognized as a limitation of this technique. With an aim to overcome this limitation, we started our investigation. In this paper, we have considered three acoustic sensors, where the sensors maintain unequal distances. Three acoustic sensors can be organized by two types of topologies, i.e., acoustic sensors in line (ASL) scheme and acoustic sensors in a triangle (AST) scheme 9. We have worked with both schemes to investigate the impact of unequal distances among the acoustic sensors. From diverse types of fish sounds, we have considered chirp sound and use its frequency for simulations. This type of sound is very common in damselfish (Dascyllus aruanus), humpback whales (Megaptera novaean-gliae), dugongs (Dugong dugon), etc., species. Firstly, we have worked to establish a theoretical impact and then we have verified the theory by simulation. In this research, MATLAB R2010a was used as our simulation tool.

The most widely of silverside fish (Atherinomorus lacunosus) populations living in Banggai waters (Central Celebes). The local name is sosodek fish, and we called Banggai Silverside Fish (BSF). This species is beneficial to the daily life of the community and has long been established as a "customary fish". Research concerning in Banggai Laut waters (Labobo and Bangkurung), has been carried out in 17 th February-17 th March 2016. The research aimed to determine exploitation status of silverside. Data collection techniques consist of sampling and interview. Sampling was conducted on 2,638 individual fish samples, and 391 individues among them for estimating growth pattern. Data analysis using quantitative methods. Silverside fish is always spawning simultaneously just in Boniton beach waters (Bangkurung), only on the night of the full moon, occurs precise at dawn, fainted after spawning, and regained consciousness when the sun rises. The fishermen catch these fish simultaneously with the fishes release their eggs. Growth pattern is " positive allometric " , and the growth status of body length is " grows very slowly ". While the rates of fishing mortality, natural mortality, exploitation and utilization indicate the level of exploitation has reached the status of " overexploited " until " depleted ". Therefore, this fish resource facing very serious problems relating to security in the resource stock. So that needs to be protected and should immediately do the stock's recovery. That should be done are prohibiting fishing activities, initiating the fish protected areas, and designing fish aggregating devise.

The Baringo barb Labeobarbus intermsdius is one of the least studied native fish species in Lake Baringo, a shallow freshwater lake located in the eastern arm of the Rift Valley, Kenya. This study evaluated aspects of its biology to provide baseline scientific information on the species. Fish were sampled using gillnets and their lengths (to the nearest 0.1 cm) and weight (to the nearest 0.1 g) measured on a meter board and electronic balance respectively. Parameters of the length-weight relationship were obtained by fitting the power equation; W=a × Lb to length and weight data. Each fish was dissected to remove the stomach for stomach content analysis. Gonads examined gonads for sexing and determination of maturity stage. Fish size in a total of 280 individual sampled during the study ranged from 6.0 to 36.0 cm total length and 4.3 to 1314 g total weight. The b value of the length-weight relationship was 3.1177 indicate positive allometric growth. Of 254 sexed individuals 107 were males and 147 were female giving a ratio of male to female to be 1:1.38 which was significantly different from the expected 1:1 sex ratio (chi-square test, p<0.05). In this study, all the maturity stages were observed except stages VI and VII in male and VII in females. The most important food items of Baringo barb in Lake Baringo were detritus, algae and seeds but other items were consumed consistently with benthic feeding. There is a need for longer-term studies on the biology of this commercially important species to provide data to guide its sustainable exploitation and conservation.