Stock Assessment of Small Pelagic Fishes Caught by Ring Net Fishery in the Camotes Sea, Central Visayas, Philippines (2003-2012) Item Type article Authors Belga, Prudencio, Jr. B.; Abrenica, Bruna T.; Paran, Johnson S.; Bacalso, Regina Therese DOI 10.31398/tpjf/25.1.2017C0009 Download date 24/09/2021 15:01:47 Link to Item http://hdl.handle.net/1834/40961 The Philippine Journal of Fisheries 25 (1): 95-106 The Philippine Journal of FisheriesJanuary-June Volume 24 (1-2):2018 _____ DOI 10.31398/tpjf/25.1.2017C0009 January - December 2017 Stock Assessment of Small Pelagic Fishes Caught by Ring Net Fishery in the Camotes Sea, Central Visayas, Philippines (2003-2012) Prudencio B. Belga, Jr.1, Bruna T. Abrenica1,*, Johnson S. Paran1, Regina Therese Bacalso2 1Bureau of Fisheries and Aquatic Resources Region VII, Arellano Blvd., Cebu City 2ECOFISH Project, Cebu Technical Office, 6F CIFC Towers, North Reclamation Area, Cebu City 6000 ABSTRACT An analysis of the ten-year data on catch, effort, and length frequency of small pelagic caught from ring net fishery in the Camotes Sea was made. Length frequency data were used to estimate growth, mortality (total, natural, and fishing mortalities) and exploitation levels using the FAO-ICLARM Fish Stock Assessment Tools (FISAT) program developed by FAO/ICLARM. Generally, the sizes of the major species caught from ring net fishery are smaller than the maximum size they can attain and were harvested before reaching maturity lengths. The probability of capture at L50, however, was higher in 2003-2012 than in 1983-1987 assessment. Analysis of the recruitment pattern in the Camotes Sea reveals a dual recruitment mode per year starting from April to June which conforms to the findings of Jabat and Dalzell (1988) of which bimodal pattern of recruitment was observed for most of the small pelagic species in the catch of the ring net fishery from the Camotes Sea and in the Philippines in general. Exploitation rate (E=F/Z) estimates of three dominant pelagic species, Decapterus macrosoma (L∞=27.56 and present E=0.71), Selar crumenophthalmus (L∞=30.03 cm and present E=0.68), and Decapterus kurroides (L∞= 41.64 and present E=0.51) revealed they are vulnerable to ring net fishery as exhibited by high E values exceeding the 0.5 threshold. The present exploitation levels suggest growth overfishing of these pelagic species which will eventually lead to unsustainable ring net fishery in the Camotes Sea. *Email: [email protected] Keywords: stock assessment, small pelagic, ring net, Camotes Sea Received: 27 May 2017 Accepted: 22 October 2017 1.INTRODUCTION In any fishery investigation, information on stock assessment is deemed necessary, particularly to he Camotes Sea is one of the most important commercially important species of fish. Information on fishing grounds in the Visayan region. The sexual maturation and sex ratio of many ring net caught area is surrounded by 11 municipalities and 4 fishes in the Camotes Sea is, however, inadequate and Tchartered cities namely Lapu-Lapu City, Mandaue City, hence an attempt has been made to study this aspect of Consolacion, Liloan, Compostela, Danao City, Carmen, fishery biology in the Camotes Sea. This report presents Catmon, Borbon, Tabogon, Bogo City, San Francisco, the findings using the data gathered by NSAP Region 7 Poro, Tudela, and Pilar. on the catch trends of the commercial ring net fishery Majority of the fisherfolks were full-time in the Camotes Sea from 2003-2012, and the population fishers with monthly income from fishing ranging from dynamics and exploitation rates of the major fish Php 1,000-6,000 for the marginal fishers to Php 20,000- resources exploited by this fishery. The results are then 100,000 for the commercial fishers. About half of the compared to the findings in an earlier study by Jabat and fisherfolks earned Php 1,000-3,000 per month, while Dalzell (1988) of the Danao ring net fishery from 1983- others were fishing for consumption only with an average 1987. monthly income of Php 2,700. Both motorized and non- motorized boats are utilized in most fishing activities 2. METHODOLOGY except in the gathering of sea cucumbers and shells. The growing importance of ring net fishing in Study site the Camotes Sea has given rise to many speculations regarding its effect on the fishery resources. Most of the The Camotes Sea is located approximately at marginal fishermen, for instance, believe that the rapid longitudes 124º 45´ E and latitudes 10º 55´ N. The area is increase in the number of commercial fishing activities bounded to the north by the Ormoc Bay and the Visayan that catch small pelagic fishes in the Camotes Sea would, Sea, to the east by the island of Leyte, to the south by the in the long run, lead to the depletion of these fishery Danajon Bank of Bohol, and to the west by the island of resources if not properly regulated. Cebu. At its center is the Camotes Island (Figure 1). The 95 The Philippine Journal of Fisheries Volume 24 (1-2): _____ The Philippine Journal of Fisheries 25 (1): 95-106 January - December 2017 via actual interviews with the fishermen. Fish samples were sorted by species, and their sample weights recorded. Fish lengths were measured in centimeters to the lower cm limit, while weight measurements were in kilograms. Data processing and analysis All data were submitted to the NSAP office in Cebu City for processing and encoding. All catch, effort, species composition, and length frequency data from the monitored landed catch of the commercial ring net operations were consolidated by month for every year into the sampling. Annual fish data were processed and analyzed using the FISAT program developed by FAO/ ICLARM. Catch landings from gillnets and hook and lines Figure 1. Gridded map of Central Visayas showing the landing centers were also monitored by the enumerators during the study of ring net fishery in Camotes Sea. period. However, because of the very limited number of landings by these municipal fishing gears at the Looc and Tabuk Looc sampling stations, their yield estimates were Camotes Sea covers a total area of 10,900 sq. km. The deep deemed not representative for the entire Camotes Sea off shelf covers 9,500 sq. km. with depths of 10-800 m. municipal fisheries production. Consequently, they were The southern portion of the northern coast of Bohol has not included in the analysis. a shelf area that covers about 1,400 sq. km. with depths ranging from 14-700 m. Catch per unit effort (CPUE) and yield estimates Sampling site The catch per unit effort (CPUE) was standardized to kg per hour of operation. The calculated Monitoring of landed catch was conducted in the mean CPUE (kg/hr) and the total number of fishing trips two major commercial fish landing sites in Danao City. made within the month, converted into total fishing Danao City fish landing area is one major landing site in hours, were used to estimate the total landed catch of the the Cebu Province. In this area, there were 179 fishing fishery on a monthly basis. Annual production estimates boats monitored by NSAP enumerators from 2003-2012 were simply the sum of the computed total monthly and 83% were ring nets, 5% purse seines, 9% gillnets, and yields. Sample weights of the fish species were raised to 3% were hook and line. the total catch per fishing trip as follows: Data collection Weight of species Total in sample landed Five (5) enumerators were hired and trained to Total weight of species in the catch = weight monitor the daily catch landings of ring nets, gillnets, X Weight of purse seines, and hook and line fishing gears from 2003- Sample 2012. The sampling scheme involved monitoring the landed catch for two successive days followed by a one- Total catch per month for each species by day interval, for an average of 22 sampling days a month. gear type was estimated using the total number of fish Data were recorded in prepared forms that included the landings by gear per month against the number of following information: landings sampled as raising factor. Monthly estimates were then consolidated to calculate the annual landings a. Name of the fishing ground for a particular fish species by gear type. Similarly, for the b. Landing center length distribution of the total catch by species for each c. Date of sampling month, a raising factor was used: d. Name of boats e. No. of fishing days of the actual operation (time) Total monthly catch of species f. Total catch by boat (no. of boxes/bañeras or weight R.F. = in kg) Sample weight of species g. Catch sample weight (kg) h. Catch composition (scientific names of the marine Catch composition and dominant species in the catch species) i. Name and signature of samplers/recorders The dominant fish species caught were determined based on the fishes’ contribution by weight Data on the fishing boat, its propulsion, gross to the total harvest from 2003-2012. All fish species were tonnage, and other relevant information were obtained then arranged through percentage ranking by order of 96 The Philippine Journal of Fisheries Volume 24 (1-2): _____ The Philippine Journal of Fisheries 25 (1): 95-106 January - December 2017 highest to lowest contribution to the total catch. Table 1. Inventory of municipal fishing gears operated in the Camotes Sea (AY2002). Seasonality of selected major species Category Fishing Gear Count Commercial Ring net 26 The mean monthly catch per unit effort (kg/ Purse seine 2 hr) was computed for the 10-year data in an attempt to Sub-total 28 determine the seasonality of the commercial ring net fishery in the Camotes Sea as a whole, and of the major Municipal Multiple handline 4,380 fishery species in the catch.