Stock Concept Research Articles

Biochemical genetic stock structure of the southern African anchovy, Engraulis capensis Gilchrist

The geographical distributions of inherited biochemical markers were used to measure the amount of genetic isolation between stocks of Namibian and South African anchovy, Engraulis capensis. A contingency‐table analysis of allele frequencies for 10 polymorphic protein‐coding loci revealed no significant frequency differences between spawning areas. The average Nei genetic distance between samples was 0.0003 and there were no geographic trends in the amount of genetic distance between populations. Average population heterozygosity for 31 loci was 0.115 and this accounted for 99.26% of the total genetic variation. The remaining 0.24% was due to all temporal and spatial differences combined. The observed amount of genetic divergence between populations was used to estimate the amount of migration between spawning areas, using the stepping‐stone model of migration. As few as 13 migrants may account for the observed genetic divergence between spawning areas. The validity of using the genetic stock concept in the management of marine fishes is discussed.

Population identification of red-fin pargo,Parargyrops edita Tanaka, in Taiwan strait and Beibu Gulf

This paper deals with population identification ofParargyrops edita Tanaka. Samples of spawning stocks were collected from Niushan-Penghu, Minnan-Taiwan shoal (Southern Fujian-Taiwan shoal) and Beibu Gulf during the spawning period 1981–1982. Morphological characters, both meristic and morphometric, are counted and measured respectively. The stock concept and intraspecific categories have been discussed. Some meristic characters as the number of left or right ventral fin spine, right ventral fin rays and abdominal vertebrae of this fish may be constant, others as the numbers of left or right pectoral fin rays and gill-rakers may have obvious geographical variation. Morphological characters have not attained the level of subspecific distinctness, no sub-species could be found among these stocks by means of coefficient of difference (C.D.). Basing upon the comparative analysis ofMdiff, the authors consider that stocks of Minnan-Taiwan shoal and Niushan-Penghu belong to the same local population, Taiwan Strait local population. By means of the discriminant function analysis and linear relationship analysis, statistical differences will be found to exist in meristic characters between the stock of Minnan-Taiwan shoal and that of Niushan-Penghu, so that the two are virtually different stocks or subpopulations. The stock of Beibu Gulf belongs to another called the Beibu Gulf local population. These two local populations are of allopatric distribution and show statistically significant difference between themselves. Among these stocks, the Minnan-Taiwan shoal stock is strongly influenced by the much more complicated environmental conditions of the mixed boundary region of the subtropical Sino-Japanese Subregion in the north and the tropical Indo-Malayan Subregion in the south. Thus its coefficient of variability (C.V.) is greater than those of the other two in the mean values of various meristic characters.

Canadian Journal of Fisheries and Aquatic Sciences. Special Issue: Volume 38, Number 12, December 1981. The Stock Concept International Symposium, Held October, 1980, Sponsored by The Great Lakes Fishery Commission, Ann Arbor, Michigan, USA. J. Watson

<i>Canadian Journal of Fisheries and Aquatic Sciences. Special Issue: Volume 38, Number 12, December 1981. The Stock Concept International Symposium, Held October, 1980, Sponsored by The Great Lakes Fishery Commission, Ann Arbor, Michigan, USA</i>. J. Watson

Homing by Canada's West Coast Herring to Management Units and Divisions as Indicated by Tag Recoveries

The change from a fishery for reduction to meal and oil to one primarily for roe resulted in major shifts in the herring fishing grounds on Canada's west coast. To meet management needs for the new fishing pattern, the former stock concept of seven "populations" was revised into 35 "management units." Reanalysis of tag recovery data for the period 1937–67, in terms of the 22 management units represented, showed a degree of homing between 66 and 96% for 18 of these management units. This is comparable to the homing displayed by the seven former populations (54–84%) estimated from essentially the same data base. Homing to some of the more isolated management units was comparable to that for the six major divisions of the coast (77–94%), as currently defined. Stevenson's (1954) conclusion "… the herring of British Columbia tend to form a series of integrating populations" is supported by the present analysis.Key words: Clupea harengus pallasi, tagging, homing, stocks, populations

The Stock Concept, Discreteness of Fish Stocks, and Fisheries Management

This paper examines the concept and definition of fish stocks and the processes that influence discreteness of these stocks in light of the tactics necessary for the application of the concept in management. Two approaches to the definition of stocks are discussed. These differ in the extent to which management inputs other than biological ones are considered. We consider definition to be less important than the adoption and development of a stock concept to provide a genetic perspective for fisheries management. The two central levels of the stock concept — the subdivision of species into local populations and the adaptive nature of genetic differences between these populations — are discussed with respect to the interlinked set of ecological and genetic processes that result in subdivision and determine the discreteness of these stocks. Genetic discreteness usually implies some restriction of gene flow, and spatial and temporal mechanisms of isolation are discussed with examples from the STOCS symposium. The structure of subdivided populations is seen as the result of behavioral processes that are one component of a set of coadapted traits, which collectively constitute a life history strategy. The necessity for managers to develop a new integrated view of species, which incorporates both ecological and genetic arguments, is discussed.Key words: stock concept, life history, gene flow, ecological and genetic discreteness, local adaptation stock management

The Stock Concept and its Application to British Columbia Salmon Fisheries

The application of the stock concept to the management of British Columbia salmon fisheries is examined in an historical context. Early recognition of the distinctiveness of runs proceeding to different rivers led to the management principle that stocks should be harvested at a rate commensurate with their abundance level and their particular reproduction rate. Past and current work has been directed largely to applying this principle and included stock identification and estimates of abundance (catch and escapement) and of age composition. However, the application of the stock concept to management has been fraught with difficulties mainly because of the large number of stocks involved, the increasing catching power of the fishing fleet, and its displacement into fishing areas where stocks are mixed extensively. Some options for future management strategies are considered, but prospects for the maintenance of all but the most productive stocks seem dim.Key words: Pacific salmon, stock concept, management, fisheries, stock–recruitment relationship

The Stock Concept and the Uncoupling of Organismal and Molecular Evolution

Evidence in support of the view that molecular evolution proceeds at a steady rate is presented in a brief review. This view of the steady rate of evolution of structural proteins, known as the molecular clock hypothesis, is shown to apply to the kinds of proteins that are commonly examined for variation by means of electrophoretic and immunological techniques in investigations of the stock structure of populations. The review is extended, with examples from the ichthyological literature, to show that the pace of organismal evolution is quite erratic in comparison to the pace of molecular evolution. A resolution of the apparent paradox regarding the uncoupling of the course of molecular and organismal evolution is offered based on the published suggestion of Allan C. Wilson and colleagues that the molecular divergence of any pair of populations should be seen as representing a time scale for the divergence. On this basis, disparities between divergences estimated from molecular and organismal data may be interpreted as reflections of the erratic pace of organismal evolution. Finally, it is suggested that the biological significance of distinctions between populations is to be seen in the summation of the organismal and molecular data.Key words: stock concept, organismal, molecular, evolution

Significance of the Stock Concept in Artificial Propagation of Salmonids in Alaska

Hatcheries could make a significant contribution to the enhancement of salmonid fisheries if application of this technology is based on principles of the stock concept. Evidence for the stock concept is reviewed and discussed in relation to transplantation of stocks, mating procedures, maintenance of genetic diversity, different methods of artificial propagation, and location of artificial propagation facilities. A strategy is developed for management of both wild and artificially propagated stocks.Key words: hatcheries, salmon, stock concept, genetics, artificial propagation

The Stock Concept from the Viewpoint of Population Genetics

Results are presented of a comparative study of the spatial and temporal structure of fish species from the standpoint of biochemical population genetics. Local fish stocks within historically established natural boundaries are considered as genetically stable population systems, in contrast to the elementary populations, which are variable structural components of such systems. The general principle in maintaining a rational fish industry is formulated on the basis of an approach to the population system as a whole, to distribute the appropriate efforts among all components of its structure.Key words: biochemical population genetics, stock concept of fish, optimal fishing industry

Perspectives and Policy Recommendations on the Relevance of the Stock Concept to Fishery Management

The Stock Concept International Symposium (STOCS) addressed a broad range of concerns about the relationship between intraspecific stocks and their genetic and environmental origins. STOCS produced an understanding of the stock concept that makes it possible to develop operational stock definitions reflecting the key elements of concern to fishery managers. These definitions can change as circumstances dictate because stocks represent states in a dynamic process. Extensive life history information available for Great Lakes fish provides a basis for estimating the significance of intraspecific stock structure in management of these species. Recognition of the potential for stock formation is important for evaluating the impact of management actions and for planning the restoration of individual species in fishery rehabilitation programs. Finally, we present a brief set of recommendations for research and management based on our perception of the stock concept and its relevance to fish community rehabilitation.Key words: fish stocks, fishery rehabilitation

Life History, Morphology, and Electrophoretic Characteristics of Five Allopatric Stocks of Lake Whitefish (Coregonus clupeaformis) in the Great Lakes Region

Ecological, morphological, and electrophoretic variation among five allopatric Ontario lake whitefish (Coregonus clupeaformis) stocks was studied. The stocks differ in terms of diet, growth rate, movement patterns, fecundity, and egg and larval size. Morphologically, the five stocks were also different for characters such as number of gill rakers, number of pyloric ceca, and in size, adjusted for fork length, of the tail, dorsal fin, and the eye. Discriminant functions, derived from body measurements and meristic counts, classified specimens accurately into their lakes of origin. Highly significant allele frequency differences were found at 6 of the 32 electrophoretic loci examined. Standard genetic distances, derived from electrophoretic allele frequency differences, corresponded roughly to the order in which these stocks became isolated following retreat of the last continental glaciation. The genetic distance of the Opeongo stock from the other stocks is about one order of magnitude larger than the genetic distances among the other stocks. The Opeongo stock is also somewhat unusual ecologically, having different egg size and fecundity characteristics compared with the other stocks and being a member of a sympatric dwarf/normal pair. Dendrograms, derived from the Mahanalobis distances for the meristic variation and the Nei genetic distances for the electrophoretic variation, showed similar branching patterns, but the branching patterns for the morphometric versus the biochemical variation were different. A significant part of the morphometric variation among the stocks was related to differences in growth rates of the stocks, most body measurements being negatively correlated with growth rate. The Mahanalobis distances for the meristic variation (including pyloric ceca counts) were correlated with the standard genetic distances from the electrophoretic data. The ecological, morphological, and biochemical variation among the stocks, in relation to local adaptation, is discussed.Key words: lake whitefish, stock concept, genotype, phenotype, ecology, morphology, meristics, multivariate analysis, electrophoresis, growth, diet, fecundity

Applications of the Stock Concept to Fish Populations in the USSR

Genetic studies of several species of marine fish conducted for over 20 years are reviewed for their application to the problem of intraspecific differentiation of fish. Cyto-physiological, biochemical, and immunological methods were used. By each of these, two sizes of Black Sea horse mackerel (Trachurus mediterraneus) were shown to be sibling species and not local stocks. Similarly, North Atlantic redfish Sebastes marinus and S. mentella were found to be separate species, in agreement with known morphological and ecological differences. In Pacific salmon, genetic markers were used to distinguish planted chums from native stocks, and indicated that such populations are maximally adapted to their historic environment. Stock differences are less apparent in pinks, but are sufficient to suggest subpopulation structure. Genetic differences are found in adjacent generations in odd and even years. Subdivision was most pronounced in sockeye salmon (Oncorhynchus nerka). Spring sockeye spawning in streams were more subject to selection pressure than were summer stocks spawning in lakes. In Atlantic salmon (Salmo salar), spawning in rivers of northern European USSR, the majority showed genetic subdivision during the spawning run. North Sea herring (Clupea harengus) tested by hemagglutination reactions showed differences that coincided with ecological subdivision at spawning, for winter–spring oceanic, summer–autumn marine, and spring–summer coastal herring. Electrophoretic determinations supported these differences. In European anchovies (Engraulis encrasicholus), stocks were differentiated by blood groups, even in the absence of spatial isolation. All of these findings indicate that elementary fish populations play an important role in differentiation and integration of the species gene pool. Efficient management of fish stocks is based on preserving the hereditary heterogeneity of their populations.Key words: genetic markers, stock differences, immunological, biochemical, physiological, intraspecific differentiation

Stocks are Chameleons: Plasticity in Gill Rakers of Coregonid Fishes

The characters that apparently render a stock of fish distinctive may in reality be a reflection of the presence or absence of other fish species with which the stock shares its environment. Over the northern hemisphere, the whitefish genera Coregonus, "Leucichthys," and Prosopium offer striking examples of morphological characters being displaced because of coinhabiting species. Whenever one of the groups is missing, another tends to shift its gill rakers so as to fill in the vacant part of the spectrum in gill-raker counts. Plankton-feeding lake whitefish (Coregonus clupeaformis) having many long gill rakers exist in several lakes sympatrically with bottom-feeding lake whitefish having fewer and shorter gill rakers, but only if the even more specialized plankton-feeding species of ciscoes are absent. Lake whitefish in Yukon Territory have on the average fewer rakers in those lakes that contain ciscoes than in those that do not. Artificial transplants demonstrate that gill-raker characteristics can change quickly in a new environment. Gill-raker count is less subject to phenotypically induced variation from environmental influences than are most morphological characters, but it is not immune. Partial hybridization, where bimodal populations are maintained by a balance between gene flow and selection, also poses special problems for the stock concept. When employing even relatively stable characters such as gill-raker counts, one should beware that the "stocks" may be chameleons which shift their appearance in response to the biological color of their surroundings.Key words: coregonids, whitefish, gill rakers, phenotypic variation, hybridization, selection, transplants, stocks

The Conundrum of the Stock Concept—Are Nature and Nurture Definable in Fishery Science?

The definition of the word stock, as applied in fishery science, is presented in general and in precise forms. The general definition is a species group, or population, of fish that maintains and sustains itself over time in a definable area. In a more precise manner, stock (genotypic) is defined as a population of fish maintaining and sustaining Castle–Hardy–Weinberg equilibrium. If a genetic basis is not available for stock characterization, then a phenotypic stock definition has to be recognized as a population of fish maintaining characteristics which are expressed in one or more ways, depending on the type or nature of environment of domicile.Key words: fish stocks, definition

Can the Reserves Approach to Monetary Control Really Work?

ON OCTOBER 6, 1979, the Board of Governors (BOG) of the Federal Reserve System announced that the Federal Open Market Committee (FOMC) was abandoning its historical preoccupation with an interest rate approach to monetary control in favor of a reserve aggregate approach.1 Underlying this new approach is the fact that, at time t, any money stock concept, M, is the product of a money multiplier, m, and a reserve aggregate, R; that is,

Interactions between Sea Lamprey (Petromyzon marinus) and their Forage Base. A Report from the SUS Stock Effects Task Force

A task force of participants convened during the course of the Sea Lamprey International Symposium considered the implications, for management of Great Lakes fisheries, of information provided about known interactions between feeding sea lampreys and the stocks of fish on which they prey. A weighted series of recommendations identified the need for more information or for changes in management practice.Key words: sea lamprey, Great Lakes, Finger Lakes, fishery management, stock concept

Perspectives on Fisheries Biology and Implications for Management

Descriptions of fisheries systems for purposes of management often seem to imply a naturally predetermined biological structure and functioning of the resource. However, such basic characteristics as stock definition, species composition, levels of production, and biological efficiency are parameters that have generally been adapted to suit particular fishery conditions and in any case are variables that interact with both environment and the nature of industrial exploitation. In the interests of economic or social analyses in fisheries these biological descriptors should normally be amenable to redefinition or redescription without prejudice to their reliability as indices of natural production. Key words: fisheries management, economic objectives, unit stock concept, variability, fisherman's choice, predator–prey relations, biological and technological efficiency

CRITERIA FOR SELECTING MATERIAL FOR A CENTRAL LENDING STOCK

The concept of a central lending stock, has attracted much attention, but it has been slow to gain acceptance because countries have thought too much in terms of ‘all or nothing’. However, a totally comprehensive collection is impossible, and quite small collections can satisfy a high proportion of interlending demand. Selection should be of categories of material rather than individual items, the selection of which would be far too complex. Literature may be categorised by form (serials, monographs, etc), subject, language, purpose (academic, etc), and extent of demand. For each category the likely ratio of acquisition cost to demand, urgency of need, and availability from other sources can thus be assessed. An analysis of this kind, of which an example is given from British experience, can help to determine which categories of material may be candidates for acquisition for a central lending stock.

Spatial Model for an Exploited Shellfish Population, and its Application to the Georges Bank Scallop Fishery

Existing fisheries models employ the "unit stock" concept that makes no explicit allowance for spatial distribution of biomass and effort over a fishing ground. The utility of the unit stock concept rests largely upon the "dynamic pool" assumption. However, this is both invalid for sedentary species, and difficult to apply when information on spatial distribution by statistical subunits is available, as for the Georges Bank (lat. 42°N, long. 67°W) scallop population. By reference to the Georges Bank scallop fishery, more realistic general assumptions for a spatial model of shellfish populations are:a) Recruitment occurs in patches of random size and location with the constraint that local biomass does not exceed the virgin biomass of each unit area.b) The fraction of effort expended within each statistical area of a fishing ground is either determined by available local biomass alone (proportional effort allocation) or in combination with "traditional fishing practice."Therefore, a spatial model (YRAREA) simulating nonrandom recruitment and harvesting of sedentary organisms is postulated and applied to Georges Bank scallop stocks. Some of the general predictions of this model differ significantly from those employing the unit stock concept, as follows:1) Under proportional effort allocation, overall yield declines more sharply with increasing effort subsequent to maximum sustained yield (MSY) than under dynamic pool assumptions. 2) Peak mortality and the apparent point of full recruitment on the catch curve occur progressively earlier in life (even at partially recruited ages) with increased effort or degree of clumping of the population, and subsequently declines with age, except where "fully recruited" ages coincide spatially with the "target" age-group making up the largest biomass component. This may be of general relevance to fisheries under intensive exploitation with sophisticated methods of navigation and fish finding; peak mortality may occur earlier in life than predicted from the gear selection ogive, if year-classes are independently distributed and there is no size limit regulation. 3) Variance in biomass/unit area is predicted to fall with age.For the Georges Bank scallop population, the model described herein predicts that a substantial increase in yield would result from diversion of effort from the Northern Edge to less heavily fished areas of the bank.

Economic Lot Size Determination in Multi-Stage Assembly Systems

We consider the optimal lot size problem for multi-stage assembly systems where each facility may have many predecessors but only a single successor. Assumptions include constant continuous final product demand, instantaneous production, and an infinite planning horizon. Costs at each facility consist of a fixed charge per lot and a linear holding cost. Under the constraint that lot sizes remain time invariant, it is proven that the optimal lot size at each facility is an integer multiple of the lot size at the successor facility. This fact is used in the construction of a dynamic programming algorithm for the computation of optimal lot sizes. The algorithm exploits the concept of echelon stock [Clark, A. J., H. Scarf. 1960. Optimal policies for a multi-echelon inventory problem. Management Sci. 6 (4, July) 475–490; Clark, A. J., H. Scarf. 1962. Approximate solution to a simple multi-echelon inventory problem. Chapter 5. K. J. Arrow et al., eds. Studies in Applied Probability and Management Science. Stanford University Press, Stanford, California.].