Growth parameters for Lates niloticus (L.), Bagrus docmak (Forsskal), Oreochromis niloticus (L.), Clarias gariepinus (Burchell) and Synodontis species derived from tag returns

In a tagging experiment carried out in the Kenyan waters of Lake Victoria, an annual growth increment of 29 cm yr was obtained for Lates niloticus (L.). Growth parameters obtained using the von Bertalanffy model on the growth curve fitted by eye were L (inf.) = 122 cm yr and k = 0.26 yr. Data for other species tagged were inadequate to obtain meaningful results.

Reported Trip Costs, Gross Revenues, and Net Returns for U.S. Atlantic Pelagic Longline Vessels

Logbook set and trip summary data (containing catch and cost information, respectively) collected by NOAA’s National Marine Fisheries Service (NMFS) were analyzed for U.S. pelagic longline vessels that participated in Atlantic fisheries in 1996. These data were augmented with vessel information from the U.S. Coast Guard. Mean fish weights and ex-vessel prices from NMFS observers and licensed seafood dealers, respectively, were used to estimate gross revenues. Comparisons revealed that net returns varied substantially by vessel size and fishing behavior (i.e. sets per trip, fishing location, season, and swordfish targeting). While the calculated economic effects of proposed regulations will depend on the descriptive statistic chosen for analysis, which itself depends on the type of analysis being conducted, results show that considering heterogeneity within this fleet can have a significant effect on predicted economic consequences.

GHERS: Greater Harvest and Economic Returns from Shrimp: Final program performance report

The Greater Harvest and Economic Returns from Shrimp (GHERS) is an initiative of Poverty Reduction by Increasing the Competitiveness of Enterprises (PRICE) project, funded by USAID. The objective of GHERS was to increase the productive capacity of existing farms and enhance quality of shrimp delivered to processors adding over $ 45 million to current sales, $10 million new investment and 14,000 new jobs. This final performance report presents the activities and achievements of the project since 2008.

Factor intensity and economic returns of alternate shrimp crop and shrimp-salt farming in the coastal areas of Bangladesh

The paper examines the factor intensity and economic returns of alternate shrimp-crop and shrimp-salt farming in the coastal areas of Bangladesh. Data were collected from 30 shrimp-crop and 30 shrimp-salt farmers, 30 shrimp farmers and 30 rice farmers from three selected coastal districts of Bangladesh. Cobb-Douglas production function model was used to determine the effect of various factors on alternate shrimp-crop farming. The chosen variables were stocking of juveniles, paddy seed, labour, fertilizers, feed and farm size of respective type of farming. The results indicated that the production function exhibited increasing remrns to scale for alternate shrimp-rice, alternate shrimp-salt and year round shrimp farming while it indicated decreasing returns for year round rice farming. Economic analysis of same system of farming indicated that higher amount of input use produced higher level of yield, gross return and net return for each type of production system.

Proceedings of the Workshop on the Okhotsk Sea and Adjacent Areas [Vladivostok, June 1995]

I REPORT OF THE PICES WORKSHOP ON THE OKHOTSK SEA AND ADJACENT AREAS (pdf, 0.1 Mb) 1. Outline of the workshop 2. Summary reports from sessions 3. Recommendations of the workshop 4. Acknowledgments II SCIENTIFIC PAPERS SUBMITTED FROM SESSIONS 1. Physical Oceanography Sessions (pdf, 4 Mb) A. Circulation and water mass structure of the Okhotsk Sea and Northwestern Pacific Valentina D. Budaeva & Vyacheslav G. Makarov Seasonal variability of the pycnocline in La Perouse Strait and Aniva Gulf Valentina D. Budaeva & Vyacheslav G. Makarov Modeling of the typical water circulations in the La Perouse Strait and Aniva Gulf region Nina A. Dashko, Sergey M. Varlamov, Young-Ho Han & Young-Seup Kim Anticyclogenesis over the Okhotsk Sea and its influence on weather Boris S. Dyakov, Alexander A. Nikitin & Vadim P. Pavlychev Research of water structure and dynamics in the Okhotsk Sea and adjacent Pacific Howard J. Freeland, Alexander S. Bychkov, C.S. Wong, Frank A. Whitney & Gennady I. Yurasov The Ohkotsk Sea component of Pacific Intermediate Water Emil E. Herbeck, Anatoly I. Alexanin, Igor A. Gontcharenko, Igor I. Gorin, Yury V. Naumkin & Yury G. Proshjants Some experience of the satellite environmental support of marine expeditions at the Far East Seas Alexander A. Karnaukhov The tidal influence on the Sakhalin shelf hydrology Yasuhiro Kawasaki On the formation process of the subsurface mixed water around the Central Kuril Islands Lloyd D. Keigwin Northwest Pacific paleohydrography Talgat R. Kilmatov Physical mechanisms for the North Pacific Intermediate Water formation Vladimir A. Luchin Water masses in the Okhotsk Sea Andrey V. Martynov, Elena N. Golubeva & Victor I. Kuzin Numerical experiments with finite element model of the Okhotsk Sea circulation Nikolay A. Maximenko, Anatoly I. Kharlamov & Raissa I. Gouskina Structure of Intermediate Water layer in the Northwest Pacific Nikolay A. Maximenko & Andrey Yu. Shcherbina Fine-structure of the North Pacific Intermediate Water layer Renat D. Medjitov & Boris I. Reznikov An experimental study of water transport through the Straits of Okhotsk Sea by electromagnetic method Valentina V. Moroz Oceanological zoning of the Kuril Islands area in the spring-summer period Yutaka Nagata Note on the salinity balance in the Okhotsk Sea Alexander D. Nelezin Variability of the Kuroshio Front in 1965-1991 Vladimir I. Ponomarev, Evgeny P. Varlaty & Mikhail Yu. Cheranyev An experimental study of currents in the near-Kuril region of the Pacific Ocean and in the Okhotsk Sea Stephen C. Riser, Gennady I. Yurasov & Mark J. Warner Hydrographic and tracer measurements of the water mass structure and transport in the Okhotsk Sea in early spring Konstantin A. Rogachev & Andrey V. Verkhunov Circulation and water mass structure in the southern Okhotsk Sea, as observed in summer, 1994 Lynne D. Talley North Pacific Intermediate Water formation and the role of the Okhotsk Sea Anatoly S. Vasiliev & Fedor F. Khrapchenkov Seasonal variability of integral water circulation in the Okhotsk Sea B. Sea ice and its relation to circulation and climate V.P. Gavrilo, G.A. Lebedev & A.P. Polyakov Acoustic methods in sea ice dynamics studies Nina M. Pestereva & Larisa A. Starodubtseva The role of the Far-East atmospheric circulation in the formation of the ice cover in the Okhotsk Sea Yoshihiko Sekine Anomalous Oyashio intrusion and its teleconnection with Subarctic North Pacific circulation, sea ice of the Okhotsk Sea and air temperature of the northern Asian continent C. Waves and tides Vladimir A. Luchin Characteristics of the tidal motions in the Kuril Straits George V. Shevtchenko On seasonal variability of tidal constants in the northwestern part of the Okhotsk Sea D. Physical oceanography of the Japan Sea/East Sea Mikhail A. Danchenkov, Kuh Kim, Igor A. Goncharenko & Young-Gyu Kim A “chimney” of cold salt waters near Vladivostok Christopher N.K. Mooers & Hee Sook Kang Preliminary results from a numerical circulation model of the Japan Sea Lev P. Yakunin Influence of ice production on the deep water formation in the Japan Sea 2. Fisheries and Biology Sessions (pdf, 2.8 Mb) A. Communities of the Okhotsk Sea and adjacent waters: composition, structure and dynamics Lubov A. Balkonskaya Exogenous succession of the southwestern Sakhalin algal communities Tatyana A. Belan, Yelena V. Oleynik, Alexander V. Tkalin & Tat’yana S. Lishavskaya Characteristics of pelagic and benthic communities on the North Sakhalin Island shelf Lev N. Bocharov & Vladimir K. Ozyorin Fishery and oceanographic database of Okhotsk Sea Victor V. Lapko Interannual dynamics of the epipelagic ichthyocen structure in the Okhotsk Sea Valentina I. Lapshina Quantitative seasonal and year-to-year changes of phytoplankton in the Okhotsk Sea and off Kuril area of the Pacific Lyudmila N. Luchsheva Biological productivity in anomalous mercury conditions (northern part of Okhotsk Sea) Inna A. Nemirovskaya Origin of hydrocarbons in the ecosystems of coastal region of the Okhotsk Sea Tatyana A. Shatilina Elements of the Pacific South Kuril area ecosystem Vyacheslav P. Shuntov & Yelena P. Dulepova Biota of the Okhotsk Sea: Structure of communities, the interannual dynamics and current status B. Abundance, distribution, dynamics of the common fishes of the Okhotsk Sea Yuri P. Diakov Influence of some abiotic factors on spatial population dynamics of the West Kamchatka flounders (Pleuronectidae) Gordon A. McFarlane, Richard J. Beamish & Larisa M. Zverkova An examination of age estimates of walleye pollock (Theragra chalcogramma) from the Sea of Okhotsk using the burnt otolith method and implications for stock assessment and management Larisa P. Nikolenko Migration of Greenland turbot (Reinhardtius hippoglossoides) in the Okhotsk Sea Galina M. Pushnikova Fisheries impact on the Sakhalin-Hokkaido herring population Vidar G. Wespestad Is pollock overfished? C. Salmon of the Okhotsk Sea: biology, abundance and stock identification Vladimir A. Belyaev, Alexander Yu. Zhigalin Epipelagic Far Eastern sardine of the Okhotsk Sea Yuri E. Bregman, Victor V. Pushnikov, Lyudmila G. Sedova & Vladimir Ph. Ivanov A preliminary report on stock status and productive capacity of horsehair crab Erimacrus isenbeckii (Brandt) in the South Kuril Strait Natalia T. Dolganova Mezoplankton distribution in the West Japan Sea Vladimir V. Efremov, Richard L. Wilmot, Christine M. Kondzela, Natalia V. Varnavskaya, Sharon L. Hawkins & Maria E. Malinina Application of pink and chum salmon genetic baseline to fishery management Vyacheslav N. Ivankov & Valentina V. Andreyeva Strategy for culture, breeding and numerous dynamics of Sakhalin salmon populations Alla M. Kovalevskaya, Natalia I. Savelyeva & Dmitry M. Polyakov Primary production in Sakhalin shelf waters Tatyana N. Krupnova Some reasons for resource reduction of Laminaria japonica (Primorye region) Lyudmila N. Luchsheva & Anatoliy I. Botsul Mercury in bottom sediments of the northeastern Okhotsk Sea Pavel A. Luk’yanov, Natalia I. Belogortseva, Alexander A. Bulgakov, Alexander A. Kurika & Olga D. Novikova Lectins and glycosidases from marine macro and micro-organisms of Japan and Okhotsk Seas Boris A. Malyarchuk, Olga A. Radchenko, Miroslava V. Derenko, Andrey G. Lapinski & Leonid L. Solovenchuk PCR-fingerprinting of mitochondrial genome of chum salmon, Oncorhynchus keta Alexander A. Mikheev Chaos and relaxation in dynamics of the pink salmon (Oncorhynchus gorbuscha) returns for two regions Yuri A. Mitrofanov & Larisa N. Lesnikova Fish-culture of Pacific Salmons increases the number of heredity defects Larisa P. Nikolenko Abundance of young halibut along the West Kamchatka shelf in 1982-1992 Sergey A. Nizyaev Living conditions of golden king crab Lithodes aequispina in the Okhotsk Sea and near the Kuril Islands Ludmila A. Pozdnyakova & Alla V. Silina Settlements of Japanese scallop in Reid Pallada Bay (Sea of Japan) Galina M. Pushnikova Features of the Southwest Okhotsk Sea herring Vladimir I. Radchenko & Igor I. Glebov Present state of the Okhotsk herring stock and fisheries outlook Alla V. Silina & Ida I. Ovsyannikova Distribution of the barnacle Balanus rostratus eurostratus near the coasts of Primorye (Sea of Japan) Galina I. Victorovskaya Dependence of urchin Strongylocentrotus intermedius reproduction on water temperature Anatoly F. Volkov, Alexander Y. Efimkin & Valery I. Chuchukalo Feeding habits of Pacific salmon in the Sea of Okhotsk and in the Pacific waters of Kuril Islands in summer 1993 Larisa M. Zverkova & Georgy A. Oktyabrsky Okhotsk Sea walleye pollock stock status Tatyana N. Zvyagintseva, Elena V. Sundukova, Natalia M. Shevchenko & Ludmila A. Elyakova Water soluble polysaccharides of some Far-Eastern seaweeds 3. Biodiversity Program (pdf, 0.2 Mb) A. Biodiversity of island ecosystems and seasides of the North Pacific Larissa A. Gayko Productivity of Japanese scallop Patinopecten yessoensis (IAY) culture in Posieta Bay (Sea of Japan) III APPENDICES 1. List of acronyms 2. List of participants (Document pdf contains 431 pages)

An assessment of development options in the longline fishery

The principal objective of this study is to evaluate the benefits that accrue to the national economies as a result of different longline operational models and licensing regimes, computed, for comparability reasons, on a per tonne basis. The primary source for the derivation of these per tonne returns was individual fisheries enterprises currently operating in the sector in the countries chosen for this study. In each case, the company disclosed to the consultant detailed financial, operational and marketing data which has enabled the findings to be based upon actual empirical data, rather than assumptions or interpretations of current practice and benefit outcomes. Data obtained related principally to the 2005 calendar year. [36pp.]

The Annual Economic Survey of Federal Gulf Shrimp Permit Holders: Report on the Design, Implementation, and Descriptive Results for 2006

This technical memorandum documents the design, implementation, data preparation, and descriptive results for the 2006 Annual Economic Survey of Federal Gulf Shrimp Permit Holders. The data collection was designed by the NOAA Fisheries Southeast Fisheries Science Center Social Science Research Group to track the financial and economic status and performance by vessels holding a federal moratorium permit for harvesting shrimp in the Gulf of Mexico. A two page, self-administered mail survey collected total annual costs broken out into seven categories and auxiliary economic data. In May 2007, 580 vessels were randomly selected, stratified by state, from a preliminary population of 1,709 vessels with federal permits to shrimp in offshore waters of the Gulf of Mexico. The survey was implemented during the rest of 2007. After many reminder and verification phone calls, 509 surveys were deemed complete, for an ineligibility-adjusted response rate of 90.7%. The linking of each individual vessel’s cost data to its revenue data from a different data collection was imperfect, and hence the final number of observations used in the analyses is 484. Based on various measures and tests of validity throughout the technical memorandum, the quality of the data is high. The results are presented in a standardized table format, linking vessel characteristics and operations to simple balance sheet, cash flow, and income statements. In the text, results are discussed for the total fleet, the Gulf shrimp fleet, the active Gulf shrimp fleet, and the inactive Gulf shrimp fleet. Additional results for shrimp vessels grouped by state, by vessel characteristics, by landings volume, and by ownership structure are available in the appendices. The general conclusion of this report is that the financial and economic situation is bleak for the average vessels in most of the categories that were evaluated. With few exceptions, cash flow for the average vessel is positive while the net revenue from operations and the “profit” are negative. With negative net revenue from operations, the economic return for average shrimp vessels is less than zero. Only with the help of government payments does the average owner just about break even. In the short-term, this will discourage any new investments in the industry. The financial situation in 2006, especially if it endures over multiple years, also is economically unsustainable for the average established business. Vessels in the active and inactive Gulf shrimp fleet are, on average, 69 feet long, weigh 105 gross tons, are powered by 505 hp motor(s), and are 23 years old. Three-quarters of the vessels have steel hulls and 59% use a freezer for refrigeration. The average market value of these vessels was $175,149 in 2006, about a hundred-thousand dollars less than the average original purchase price. The outstanding loans averaged $91,955, leading to an average owner equity of $83,194. Based on the sample, 85% of the federally permitted Gulf shrimp fleet was actively shrimping in 2006. Of these 386 active Gulf shrimp vessels, just under half (46%) were owner-operated. On average, these vessels burned 52,931 gallons of fuel, landed 101,268 pounds of shrimp, and received $2.47 per pound of shrimp. Non-shrimp landings added less than 1% to cash flow, indicating that the federal Gulf shrimp fishery is very specialized. The average total cash outflow was $243,415 of which $108,775 was due to fuel expenses alone. The expenses for hired crew and captains were on average $54,866 which indicates the importance of the industry as a source of wage income. The resulting average net cash flow is $16,225 but has a large standard deviation. For the population of active Gulf shrimp vessels we can state with 95% certainty that the average net cash flow was between $9,500 and $23,000 in 2006. The median net cash flow was $11,843. Based on the income statement for active Gulf shrimp vessels, the average fixed costs accounted for just under a quarter of operating expenses (23.1%), labor costs for just over a quarter (25.3%), and the non-labor variable costs for just over half (51.6%). The fuel costs alone accounted for 42.9% of total operating expenses in 2006. It should be noted that the labor cost category in the income statement includes both the actual cash payments to hired labor and an estimate of the opportunity cost of owner-operators’ time spent as captain. The average labor contribution (as captain) of an owner-operator is estimated at about $19,800. The average net revenue from operations is negative $7,429, and is statistically different and less than zero in spite of a large standard deviation. The economic return to Gulf shrimping is negative 4%. Including non-operating activities, foremost an average government payment of $13,662, leads to an average loss before taxes of $907 for the vessel owners. The confidence interval of this value straddles zero, so we cannot reject, with 95% certainty, that the population average is zero. The average inactive Gulf shrimp vessel is generally of a smaller scale than the average active vessel. Inactive vessels are physically smaller, are valued much lower, and are less dependent on loans. Fixed costs account for nearly three quarters of the total operating expenses of $11,926, and only 6% of these vessels have hull insurance. With an average net cash flow of negative $7,537, the inactive Gulf shrimp fleet has a major liquidity problem. On average, net revenue from operations is negative $11,396, which amounts to a negative 15% economic return, and owners lose $9,381 on their vessels before taxes. To sustain such losses and especially to survive the negative cash flow, many of the owners must be subsidizing their shrimp vessels with the help of other income or wealth sources or are drawing down their equity. Active Gulf shrimp vessels in all states but Texas exhibited negative returns. The Alabama and Mississippi fleets have the highest assets (vessel values), on average, yet they generate zero cash flow and negative $32,224 net revenue from operations. Due to their high (loan) leverage ratio the negative 11% economic return is amplified into a negative 21% return on equity. In contrast, for Texas vessels, which actually have the highest leverage ratio among the states, a 1% economic return is amplified into a 13% return on equity. From a financial perspective, the average Florida and Louisiana vessels conform roughly to the overall average of the active Gulf shrimp fleet. It should be noted that these results are averages and hence hide the variation that clearly exists within all fleets and all categories. Although the financial situation for the average vessel is bleak, some vessels are profitable. (PDF contains 101 pages)

U.S. Caribbean fish trap fishery costs and earnings study

Executive Summary: This study describes the socio-economic characteristics of the U.S. Caribbean trap fishery that encompasses the Commonwealth of Puerto Rico and Territory of the U.S. Virgin Islands. In-person interviews were administered to one hundred randomly selected trap fishermen, constituting nearly 25% of the estimated population. The sample was stratified by geographic area and trap tier. The number of traps owned or fished to qualify for a given tier varied by island. In Puerto Rico, tier I consisted of fishermen who had between 1-40 fish traps, tier II was made up of fishermen who possessed between 41 and 100 fish traps, and tier III consisted of fishermen who held in excess of 100 fish traps. In St. Thomas and St. John, tier I was composed of fishermen who held between 1 and 50 fish traps, tier II consisted of fishermen who had between 51-150 fish traps and tier III was made up of fishermen who had in excess of 150 fish traps. Lastly, in St. Croix, tier I was made up of fishermen who had less than 20 fish traps and tier II consisted of fishermen who had 20 or more fish traps. The survey elicited information on household demographics, annual catch and revenue, trap usage, capital investment on vessels and equipment, fixed and variable costs, behavioral response to a hypothetical trap reduction program and the spatial distribution of traps. The study found that 79% of the sampled population was 40 years or older. The typical Crucian trap fisherman was older than their Puerto Rican and St. Thomian and St. Johnian counterparts. Crucian fishermen’s average age was 57 years whereas Puerto Rican fishermen’s average age was 51 years, and St. Thomian and St. Johnian fishermen’s average age was 48 years. As a group, St. Thomian and St. Johnian fishermen had 25 years of fishing experience, and Puerto Rican and Crucian fishermen had 30, and 29 years, respectively. Overall, 90% of the households had at least one dependent. The average number of dependents across islands was even, ranging between 2.8 in the district of St. Thomas and St. John and 3.4 in the district of St. Croix. The percentage utilization of catch for personal or family use was relatively low. Regionally, percentage use of catch for personal or family uses ranged from 2.5% in St. Croix to 3.8% in the St. Thomas and St. John. About 47% of the respondents had a high school degree. The majority of the respondents were highly dependent on commercial fishing for their household income. In St. Croix, commercial fishing made up 83% of the fishermen’s total household income, whereas in St. Thomas and St. John and Puerto Rico it contributed 74% and 68%, respectively. The contribution of fish traps to commercial fishing income ranged from 51% in the lowest trap tier in St. Thomas and St. John to 99% in the highest trap tier in St. Croix. On an island basis, the contribution of fish traps to fishing income was 75% in St. Croix, 61% in St. Thomas and St. John, and 59% in Puerto Rico. The value of fully rigged vessels ranged from $400 to $250,000. Over half of the fleet was worth $10,000 or less. The St. Thomas and St. John fleet reported the highest mean value, averaging $58,518. The Crucian and Puerto Rican fleets were considerably less valuable, averaging $19,831 and $8,652, respectively. The length of the vessels ranged from 14 to 40 feet. Fifty-nine percent of the sampled vessels were at least 23 feet in length. The average length of the St. Thomas and St. John fleet was 28 feet, whereas the fleets based in St. Croix and Puerto Rico averaged 21 feet. The engine’s propulsion ranged from 8 to 400 horsepower (hp). The mean engine power was 208 hp in St. Thomas and St. John, 108 hp in St. Croix, and 77 hp in Puerto Rico. Mechanical trap haulers and depth recorders were the most commonly used on-board equipment. About 55% of the sampled population reported owning mechanical trap haulers. In St. Thomas and St. John, 100% of the respondents had trap haulers compared to 52% in Puerto Rico and 20% in St. Croix. Forty-seven percent of the fishermen surveyed stated having depth recorders. Depth recorders were most common in the St. Thomas and St. John fleet (80%) and least common in the Puerto Rican fleet (37%). The limited presence of emergency position indication radio beacons (EPIRBS) and radar was the norm among the fish trap fleet. Only 8% of the respondents had EPIRBS and only 1% had radar. Interviewees stated that they fished between 1 and 350 fish traps. Puerto Rican respondents fished on average 39 fish traps, in contrast to St. Thomian and St. Johnian and Crucian respondents, who fished 94 and 27 fish traps, respectively. On average, Puerto Rican respondents fished 11 lobster traps, and St. Thomian and St. Johnian respondents fished 46 lobster traps. None of the Crucian respondents fished lobster traps. The number of fish traps built or purchased ranged between 0 and 175, and the number of lobster traps built or bought ranged between 0 and 200. Puerto Rican fishermen on average built or purchased 30 fish traps and 14 lobster traps, and St. Thomian and St. Johnian fishermen built or bought 30 fish traps and 11 lobster traps. Crucian fishermen built or bought 25 fish traps and no lobster traps. As a group, fish trap average life ranged between 1.3 and 5 years, and lobster traps lasted slightly longer, between 1.5 and 6 years. The study found that the chevron or arrowhead style was the most common trap design. Puerto Rican fishermen owned an average of 20 arrowhead traps. St. Thomian and St. Johnian and Crucian fishermen owned an average of 44 and 15 arrowhead fish traps, respectively. The second most popular trap design was the square trap style. Puerto Rican fishermen had an average of 9 square traps, whereas St. Thomian and St. Johnian fishermen had 33 traps and Crucian fishermen had 2 traps. Antillean Z (or S) -traps, rectangular and star traps were also used. Although Z (or S) -traps are considered the most productive trap design, fishermen prefer the smaller-sized arrowhead and square traps because they are easier and less expensive to build, and larger numbers of them can be safely deployed. The cost of a fish trap, complete with rope and buoys, varied significantly due to the wide range of construction materials utilized. On average, arrowhead traps commanded $94 in Puerto Rico, $251 in St. Thomas and St. John, and $119 in St. Croix. The number of trips per week ranged between 1 and 6. However, 72% of the respondents mentioned that they took two trips per week. On average, Puerto Rican fishermen took 2.1 trips per week, St. Thomian and St. Johnian fishermen took 1.4 trips per week, and Crucian fishermen took 2.5 trips per week. Most fishing trips started at dawn and finished early in the afternoon. Over 82% of the trips lasted 8 hours or less. On average, Puerto Rican fishermen hauled 27 fish traps per trip whereas St. Thomian and St. Johnian fishermen and Crucian fishermen hauled 68 and 26 fish traps per trip, respectively. The number of traps per string and soak time varied considerably across islands. In St. Croix, 84% of the respondents had a single trap per line, whereas in St. Thomas and St. John only 10% of the respondents had a single trap per line. Approximately, 43% of Puerto Rican fishermen used a single trap line. St. Thomian and St. Johnian fishermen soaked their traps for 6.9 days while Puerto Rican and Crucian fishermen soaked their traps for 5.7 and 3.6 days, respectively. The heterogeneity of the industry was also evidenced by the various economic surpluses generated. The survey illustrated that higher gross revenues did not necessarily translate into higher net revenues. Our analysis also showed that, on average, vessels in the trap fishery were able to cover their cash outlays, resulting in positive vessel income (i.e., financial profits). In Puerto Rico, annual financial profits ranged from $4,760 in the lowest trap tier to $32,467 in the highest tier, whereas in St. Thomas and St. John annual financial profits ranged from $3,744 in the lowest tier to $13,652 in the highest tier. In St. Croix, annual financial profits ranged between $9,229 and $15,781. The survey also showed that economic profits varied significantly across tiers. Economic profits measure residual income after deducting the remuneration required to keep the various factors of production in their existing employment. In Puerto Rico, annual economic profits ranged from ($9,339) in the lowest trap tier to $ 8,711 in the highest trap tier. In St. Thomas and St. John, annual economic profits ranged from ($7,920) in the highest tier to ($18,486) in the second highest tier. In St. Croix, annual economic profits ranged between ($7,453) to $10,674. The presence of positive financial profits and negative economic profits suggests that higher economic returns could be earned from a societal perspective by redirecting some of these scarce capital and human resources elsewhere in the economy. Furthermore, the presence of negative economic earnings is evidence that the fishery is overcapitalized and that steps need to be taken to ensure the long-run economic viability of the industry. The presence of positive financial returns provides managers with a window of opportunity to adopt policies that will strengthen the biological and economic performance of the fishery while minimizing any adverse impacts on local fishing communities. Finally, the document concludes by detailing how the costs and earnings information could be used to develop economic models that evaluate management proposals. (PDF contains 147 pages)

Changes in the size structure of the yellowfin tuna population of the tropical eastern Pacific Ocean from 1947 to 1955

ENGLISH: Morphometric studies by Godsil (1948), Godsil and Greenhood (1951), Royce (1953) and Schaefer (1952, 1955) have indicated that the yellowfin tuna of the Eastern Pacific are distinct from those of the Central Pacific. Tagging of yellowfin tuna by the California Department of Fish and Game, and by the Inter-American Tropical Tuna Commission in the Eastern Pacific, and by the Pacific Oceanic Fishery Investigations in the Central Pacific, have not yet revealed any migrations between these areas. Shimada and Schaefer (1956) have compared changes in population abundance and fishing intensity, considering the population in the Eastern Pacific as a separate entity. They conclude " ... the amount of fishing has had a real effect upon the stock of Eastern Pacific yellowfin tuna, taken in the aggregate, over the period studied. The evidence suggests also that for this species the intensity of fishing in some recent years has reached and might have even exceeded the level corresponding to the maximum equilibrium yield." Tagging experiments by the California Department of Fish and Game and by the Inter-American Tropical Tuna Commission have yielded returns in the order of one to five percent (Roedel 1954, and unpublished data of both agencies), a level much lower than that at which fishing intensity would be expected to noticeably affect the population size. These results are probably a reflection of the inadequacies of the present tagging methods, but they could lend doubt to the conclusions of Shimada and Schaefer. It is desirable, therefore, to examine other, independent, evidence as to the effects of fishing on the population. At the high levels of fishing intensity suggested by Shimada and Schaefer, in addition to changes in quantity, measurable changes would be expected to have occurred in the quality of the yellowfin tuna stocks, because the average age and size of the fish would have been reduced by the high mortality rates accompanying high fishing intensities. A continuing regular program of sampling catches and determining their length composition, to assess changes in the size composition of the stocks, was initiated by the Commission in 1954 but direct measurements are not available for the earlier, more dynamic period of growth of the fishery. Consequently, other, more general indications of possible changes in the size composition were sought. SPANISH: Los estudios morfométricos efectudos por Godsil (1948), Godsil y Greenhood (1951), Royce (1953) y Schaefer (1952, 1955), han demostrado que el atún aleta amarilla del Pacífico Oriental es distinto del que habita el PacÍfico Central. Los experimentos del Departamento de Pesca y Caza de California y de la Comisión Interamericana del Atún Tropical en el Pacífico Oriental, así como los de las Investigaciones Pesqueras del Océano Pacífico en el Pacífico Central,consistentes en la marcación de atunes aleta amarilla, aún no han puesto de manifiesto movimientos migratorios entre dichas áreas. Shimada y Schaefer (1956) han hecho estudios comparativos sobre la abundancia de la población y la intensidad de la pesca, considerando a la población del Pacífico Oriental como una entidad separada. Su conclusión es que " ... la intensidad de la pesca ha tenido un definido efecto sobre la población del atún aleta amarilla del Pacífico Oriental, tomada en conjunto, a lo largo del período estudiado. La evidencia de que se dispone sugiere así mismo que, por lo que hace a esta especie, la intensidad de la pesca en los últimos años ha alcanzado y quizás aún sobrepasado el nivel correspondiente a la máxima pesca de equilibrio". Los experimentos de mar•cación del Departamento de Pesca y Caza de California y de la Comisión Interamericana del Atún Tropical han producido recuperaciones ,entre el uno y el cinco por ciento (Roedel 1954 y datos inéditos de ambos organismos), lo que constituye un nivel mucho más bajo de aquél en que la intensidad de la pesca podría considerarse que afectaría notablemente el tamaño de la población. Estos resultados reflejan probablemente lo inadecuados que son aún los métodos de marcación, pero ellos podrían, quizá, poner en tela de juicio las conclusiones de Shimada y Schaefer. Por lo tanto,es deseable examinar otras fuentes de evidencia independientes, relacionadas con el efecto que la pesca tiene sobre la población. En efecto, si los altos índices de pesca sugeridos por Shimada y Schaefer son correctos, es de esperar que, además de los cambios en la magnitud de la población, se hayan producido otros, concomitantes y sensibles, en la calidad de los stocks de atún aleta amarilla, puesto que tanto el promedio de edad como el de tamaño de los individuos habrían disminuído debido a las elevadas tasas de mortalidad inherentes a las altas intensidades de pesca. En 1954 la Comisión inició un programa ininterrumpido para tomar muestras y determinar en ellas las frecuencias de tallas y evaluar de este modo los cambios correlativos que tuvieran lugar en los stocks pero, infortunadamente, este sistema de evaluación directa no fué practicado en el período anterior, que fué precisamente el de rápida expansión de la pesquería. En tal virtud, hubo de ser necesario buscar indicios más generales referentes a los cambios posibles en la composición de tamaños. (PDF contains 20 pages.)

Review of geographical stocks of tropical dolphins (Stenella spp. and Delphinus delphis) in the eastern Pacific

Information on geographical variation is reviewed for Stenella attenuata, S. longirostris, S. coeruleoalba, and Delphinus delphis in the eastern tropical Pacific, and boundaries for potential management units are proposed. National Marine Fisheries Service and Inter-American Tropical Tuna Commission sighting records made from 1979 to 1983 which were outside boundaries used in a 1979 assessment were examined for validity. Tagging returns and morphological data were also analyzed. Several stock ranges are expanded or combined. Three management units are proposed for S. attenuata: the coastal, northern offshore, and southern offshore spoiled dolphins. Four management units are proposed for S. longirostris: the Costa Rican, eastern, northern whitebelly, and southern whitebelly spinner dolphins. Two provisional management units are proposed for S. coeruleoalba: the northern and southern striped dolphins. Five management units (two of which are provisional) are proposed for D. delphis: the Baja neritic, northern, central, southern, and Guerrero common dolphins. Division into management units was based on morphological stock differences and distributional breaks. (PDF file contains 34 pages.)

Some aspects of the age and growth of the anchoveta, Cetengraulis mysticetus, in the Gulf of Panama

ENGLISH: Length-frequency samples of anchovetas were collected from January 1956 to March 1963. The findings for the most part corroborate those of previous studies in regard to the general pattern of age and growth. Recent tag returns demonstrate that some of the fish survive at least to the beginning of their fourth year of life. In 1961 and 1962 the fish were considerably larger than in any previous year for which data are available. The annual variation in the size of the young of the year is apparently related to the amount of upwelling and the density of the population during the early months of the year. SPANISH: De enero de 1956 a marzo de 1963 se recolectaron muestras de las frecuencias de longitud de las anchovetas. Las investigaciones, en su mayor parte, corraboran los resultados de los estudios anteriores referentes a los patrones generales de la edad y el crecimiento. Recobros recientes de mareas demuestran que algunos de los peces sobreviven por lo menos hasta el comienzo de su cuarto año de vida. En 1961 y 1962 los peces fueron considerablemente más grandes que en cualquiera de los años anteriores de los que se tienen datos disponibles. La variación anual en el tamaño de los peces jóvenes del año está aparentemente relacionada con el volumen del afloramiento y la densidad de la población durante los primeros meses del año. (PDF contains 51 pages)

Population dynamics of the skipjack tuna (Katsuwonus pelamis) of the Eastern Pacific Ocean

ENGLISH: Catches of skipjack tuna supporting major fisheries in parts of the western, central and eastern Pacific Ocean have increased in recent years; thus, it is important to examine the dynamics of the fishery to determine man's effect on the abundance of the stocks. A general linear hypothesis model was developed to standardize fishing effort to a single vessel size and gear type. Standardized effort was then used to compute an index of abundance which accounts for seasonal variability in the fishing area. The indices of abundance were highly variable from year to year in both the northern and southern areas of the fishery but indicated a generally higher abundance in the south. Data from 438 fish tagged and recovered in the eastern Pacific Ocean were used to compute growth curves. A least-squares technique was used to estimate the parameters of the von Bertalanffy growth function. Two estimates of the parameters were made by analyzing the same data in different ways. For the first set of estimates, K= 0.819 on an annual instantaneous basis and L= 729 mm; for the second, K = 0.431 and L=881. These compared well with estimates derived using the Chapman-Richards growth function, which includes the von Bertalanffy function as a special case. It was concluded that the latter function provided an adequate empirical fit to the skipjack data since the more complicated function did not significantly improve the fit. Tagging data from three cruises involving 8852 releases and 1777 returns were used to compute mortality rates during the time the fish were in the fishery. Two models were used in the analyses. The best estimates of the catchability coefficient (q) in the north and south were 8.4 X 10- 4 and 5.0 X 10- 5 respectively. The other loss rate (X), which included losses due to emigration, natural mortality and mortality due to carrying a tag, was 0.14 on an annual instantaneous basis for both areas. To detect the possible effect of fishing on abundance and total yield, the relation between abundance and effort and between total catch and effort was examined. It was found that at levels of intensity observed in the fishery, fishing does not appear to have had any measurable effect on the stocks. It was concluded therefore that the total catch could probably be increased by substantially increasing total effort beyond the present level, and that the fluctuations in abundance are fishery-independent. The estimates of growth, mortality and fishing effort were used to compute yield-per-recruitment isopleths for skipjack in both the northern and southern areas. For a size at first entry of about 425 mm, the yield per recruitment was calculated at 3 pounds in the north and 1.5 pounds in the south. In both areas it would be possible to increase the yield per recruitment by increasing fishing effort. It was not possible to assess potential production of the skipjack stocks fished in the eastern Pacific, except to note that the fishery had not affected their abundance and that they were certainly under-exploited. It was concluded that the northern and southern stocks could support increased harvests, especially the latter. SPANISH: Las capturas de atún barrilete que sostienen las pesquerías principales de la parte occidental, central y oriental del Océano Pacífico han aumentado en los últimos años; así que es importante examinar la dinámica de la pesquería para determinar el efecto que pueda tener sobre la abundancia de los stocks. Se desarrolló un modelo hipotético, lineal para standardizar el esfuerzo de pesca a un solo tamaño de barco y tipo de arte. Luego se usó el esfuerzo standardizado para computar un índice de la abundancia que pueda dar razón de la variabilidad estacional en el área de pesca. Los índices de la abundancia variaron mucho de un año a otro tanto en el área septentrional como en el área meridional de la pesquería, pero indicaron una abundancia generalmente superior en el sur. Se emplearon los datos de 438 peces marcados y recuperados en el Océano Pacífico oriental para computar las curvas de crecimiento. Una técnica de mínimos cuadrados fue usada para estimar los parámetros de la función de crecimiento de van Bertalanffy. Se hicieron dos estimativos de los parámetros mediante el análisis de los mismos datos, de diferente manera. Para el primer juego de estimativos, K=0.819 sobre una base anual instantánea y L∞=729 mm; para el segundo, K=0.431 y L∞=881. Estos se correlacionaron bien con los estimativos obtenidos usando la función de crecimiento de Chapman-Richards, que incluye la de von Bertalanffy como un caso especial. Se decidió que la última función proveía un ajuste empírico, adecuado a los datos del barrilete, ya que la función más complicada no mejoró significativamente el ajuste. Los datos de marcación de tres cruceros incluyendo 8852 liberaciones y 1777 retornos, fueron usados para computar las tasas de mortalidad durante el tiempo en que los peces estuvieron en la pesquería. Se usaron dos modelos en los análisis. Los mejores estimativos del coeficiente de capturabilidad (q) en el norte y en el sur fueron 8.4 X 10-4 y 5.0 X 10-5 , respectivamente. La otra tasa de pérdida (X), la cual incluyó pérdidas debidas a la emigración, mortalidad natural y mortalidad debida a llevar una marca, fue 0.14 sobre una base anual instantánea para las dos áreas. Con el fin de descubrir el efecto que posiblemente pueda tener la pesca sobre la abundancia y el rendimiento total, se examinó la relación entre la abundancia y el esfuerzo y entre la captura total y el esfuerzo. Se encontró que a los niveles de la intensidad observada en la pesquería, la pesca no parece haber tenido ningún efecto perceptible en los stocks. Por lo tanto se decidió que mediante un aumento substancial del esfuerzo total, más allá del nivel actual, la captura total probablemente podría aumentarse, y que las fluctuaciones de la abundancia son independientes de la pesquería. Los estimativos del crecimiento, mortalidad y esfuerzo de pesca fueron usados para computar las isopletas del rendimiento por recluta del barrilete, tanto en las áreas del norte como del sur. Para una talla de primera entrada de unos 425 mm, el rendimiento por recluta fue calculado en 3 libras en el norte y 1.5 libras en el sur. En ambas áreas sería posible aumentar el rendimiento por recluta mediante un aumento del esfuerzo de pesca. No fue posible determinar la producción potencial de los stocks del barrilete pescado en el Pacífico oriental, excepto para observar que la pesquería no ha afectado su abundancia y que ciertamente se encuentran subexplotados. Se concluyó que los stocks norte y sur pueden soportar un aumento en el rendimiento, especialmente este último. (PDF contains 274 pages.)

Estimates of the rates of mortality of yellowfin tuna in the Eastern Pacific Ocean derived from tagging experiments

ENGLISH: Tag release and return data for the Baja California and Gulf of Guayaquil areas were selected for this study because substantial numbers of returns resulted from these releases and because the effects of emigration are small in these areas. The returns of tags per unit of fishing effort for several experiments in each area were used to estimate the coefficients of total mortality and shedding. The coefficient of annual natural mortality was estimated to be less than 2.0, which is in agreement with a previous estimate of 0.8, but does not improve upon it. The estimates for the average coefficients of catchability are 2.02 X 10-3 for the Baja California area and 0.67 X 10-3 for the Gulf of Guayaquil area. SPANISH: Se seleccionaron para este estudio algunos da tos de liberación y retorno de marcas en las áreas de Baja California y el Golfo de Guayaquil debido a que cantidades substanciales de retornos resultaron de estas liberaciones y porque los efectos de migración son pequeños en estas áreas. Los retornos de marcas por unidad de esfuerzo de pesca de varios experimentos en cada área fueron empleados para estimar los coeficientes de mortalidad total y desprendimiento. Se estimó que el coeficiente de mortalidad natural anual fue inferior a 2.0, lo que está de acuerdo con una estimación anterior de 0.8, pero no la mejora. Las estimaciones de los coeficientes promedios de capturabilidad son 2.02 X 10-3 en el área de Baja California y 0.67 X 10-3 en el área del Golfo de Guayaquil. (PDF contains 58 pages.)