Homeostatic Characteristics of Single Species Fish Stocks in Arctic Lakes

1983 ◽  
Vol 40 (7) ◽  
pp. 987-1024 ◽  
Author(s):  
Lionel Johnson
Keyword(s):  
Stock Returns ◽  
Dominant Species ◽  
Size Structure ◽  
Arctic Charr ◽  
Arctic Lakes ◽  
Large Individual ◽  
Total Biomass ◽  
Length Frequency ◽  
Initial State ◽  
Fish Stocks

The results of investigations on the fish stocks of seven Arctic lakes covering a period of 23 yr are described. These lakes have remained largely undisturbed since their formation in late glacial times; all but one are completely autonomous and of comparatively small size. Such lakes provide a unique opportunity for the development and testing of conceptual models. In all cases the only fish species present is Arctic charr, Salvelinus alpinus. Length frequency distributions derived from gillnet catch curves are shown to be, within reasonable limits, representative of the actual populations in the lake, and not artifacts of the sampling procedure. Length frequency curves show a unimodal or bimodal distribution and this structure, in the absence of perturbation, appears to remain constant indefinitely. Individuals are of great age but age-at-length is highly variable. Age and size structure are shown to be comparable with the age and size structure of the dominant tree species in a climax forest; it is concluded that forces of great generality fashion these configurations. It is hypothesized that all species tend to move towards a state of least energy dissipation; this can be most readily seen in the dominant species at the climax in an autonomous system. The dominant species is characterized by large individual size, a high degree of uniformity, high total biomass, great mean age, indeterminate age-at-death, and a low incidence of replacement stock. After severe perturbation it is shown that the charr stock returns to a state of least dissipation without oscillation. Absence of oscillation during the return to the initial state, combined with the long-term stability shown in control lakes, indicates the presence of an effective damping mechanism; this in turn indicates the existence of organization within the stock as a whole. Organization develops through an interactive mechanism described under the doctrine of homeokinesis, which is responsible for energy equipartitioning and the maintenance of uniformity. These concepts help to explain phenomena observed in more complex systems and help our understanding of ecosystem functioning.

Derivation of Average Lengths of Different Age-Groups in Fishes

1969 ◽  
Vol 26 (11) ◽  
pp. 3073-3076 ◽  
Author(s):  
V. G. Jhingran ◽  
A. V. Natarajan
Keyword(s):  
Average Length ◽  
Age Groups ◽  
Length Frequency ◽  
Average Growth Rate ◽  
Average Growth ◽  
Fish Stocks ◽  
Growth Variation ◽  
Modal Values ◽  
The Tropics ◽  
Length Frequency Analysis

Fishes in general show much growth variation between years from environmental influences, food availability, and stock density, and this variation is especially more pronounced in the tropics. Average growth rate and average length at age of constituent age-groups of fish stocks, under the circumstances, appear more appropriate especially for yield computations. By the method elaborated in this note, the modal values of sizes of constituent age-groups (derived from Petersen's method of length-frequency analysis) as obtained each month for all months over a number of years (9 years, in the present case, covering the period 1957–65) are simultaneously plotted and this results in as many oblique rows as there are age-groups. Regression lines corresponding to the oblique rows of scatters of modal plots are statistically derived and used to read off the average lengths at ages. The slopes of the lines represent the average growth rates for the size ranges delimited by regression lines.

Community Response to Cumulative Toxic Impact: Effects of Acclimation on Zinc Tolerance of Aufwuchs

1992 ◽  
Vol 49 (10) ◽  
pp. 2155-2163 ◽  
Author(s):  
B. R. Niederlehner ◽  
John Cairns Jr.
Keyword(s):  
Second Generation ◽  
Community Response ◽  
Artificial Substrates ◽  
Community Respiration ◽  
Additional Stress ◽  
Total Biomass ◽  
Secondary Stress ◽  
Initial State ◽  
Zinc Tolerance ◽  
Zn Stress

Aufwuchs communities were developed on artificial substrates in a local pond. Second-generation communities were developed on identical substrates in laboratory systems receiving three levels of zinc (Zn): background, 73, and 172 μg∙L−1. After 21 d, second-generation communities were exposed to five concentrations of Zn ranging from background to 10 078 μg∙L−1 for 48 h. Protozoan communities developed under Zn stress were initially less rich taxonomically but subsequently lost fewer species in response to acute Zn exposures. Richness remaining after exposure to high Zn levels [Formula: see text] was similar for all groups. Taxonomic composition changed less in acclimated communities than in the control in response to secondary stress. Gross primary productivity was less impaired by secondary stress in communities acclimated to Zn. Community respiration, algal biomass, total biomass, respiration to biomass ratios, and ratios of soluble to total reactive phosphates did not differ in response to secondary stress. In general, communities developed under Zn stress were initially impaired but changed less in response to additional stress relative to their initial state.

scholarly journals Bayesian spatial multispecies modelling to assess pelagic fish stocks from acoustic- and trawl-survey data

2012 ◽  
Vol 69 (1) ◽  
pp. 95-104 ◽  
Author(s):  
Teppo Juntunen ◽  
Jarno Vanhatalo ◽  
Heikki Peltonen ◽  
Samu Mäntyniemi
Keyword(s):  
Spatial Distribution ◽  
Survey Data ◽  
Spatial Model ◽  
Pelagic Fish ◽  
Clupea Harengus ◽  
Environmental Data ◽  
Total Biomass ◽  
Trawl Survey ◽  
Linear Predictor ◽  
Fish Stocks

Abstract Juntunen, T., Vanhatalo, J., Peltonen, H., and Mäntyniemi, S. 2012. Bayesian spatial multispecies modelling to assess pelagic fish stocks from acoustic- and trawl-survey data. – ICES Journal of Marine Science, 69: 95–104. A Bayesian spatial model was constructed to estimate the abundance of multiple fish species in a pelagic environment. Acoustic- and trawl-survey data were combined with environmental data to predict the spatial distribution of (i) the acoustic backscattering of fish, (ii) the relative proportion of each species, and (iii) their mean length in the Gulf of Finland in the northeastern Baltic Sea. By combining the three spatial model layers, the spatial distribution of the biomass of each species was estimated. The model consists of a linear predictor on environmental variables and a spatial random effect given by a Gaussian process. A Bayesian approach is a natural choice for the task because it provides a theoretically justified means of summarizing the uncertainties from various model layers. In the study area, three species dominate pelagic waters: sprat (Sprattus sprattus), herring (Clupea harengus), and three-spined stickleback (Gasterosteus aculeatus). Results are presented for each model layer and for estimated total biomass for each species in 2 × 2 km lattices. The posterior mean and central 95% credible intervals of total biomass were sprat 45.7 kt (27.7–71.6), herring 24.6 kt (9.7–41.3), and three-spined stickleback 1.9 kt (0.9–3.2).

scholarly journals Potential impacts of climate change on Northeast Pacific marine foodwebs and fisheries

2011 ◽  
Vol 68 (6) ◽  
pp. 1217-1229 ◽  
Author(s):  
C. H. Ainsworth ◽  
J. F. Samhouri ◽  
D. S. Busch ◽  
W. W. L. Cheung ◽  
J. Dunne ◽  
...  
Keyword(s):  
Climate Change ◽  
Functional Groups ◽  
Size Structure ◽  
Zooplankton Community ◽  
Cumulative Effects ◽  
Total Biomass ◽  
Community Size ◽  
Climate Effects ◽  
Northeast Pacific ◽  
Impacts Of Climate Change

Abstract Ainsworth, C. H., Samhouri, J. F., Busch, D. S., Cheung, W. W. L., Dunne, J., and Okey, T. A. 2011. Potential impacts of climate change on Northeast Pacific marine foodwebs and fisheries. – ICES Journal of Marine Science, 68: 1217–1229. Although there has been considerable research on the impacts of individual changes in water temperature, carbonate chemistry, and other variables on species, cumulative impacts of these effects have rarely been studied. Here, we simulate changes in (i) primary productivity, (ii) species range shifts, (iii) zooplankton community size structure, (iv) ocean acidification, and (v) ocean deoxygenation both individually and together using five Ecopath with Ecosim models of the northeast Pacific Ocean. We used a standardized method to represent climate effects that relied on time-series forcing functions: annual multipliers of species productivity. We focused on changes in fisheries landings, biomass, and ecosystem characteristics (diversity and trophic indices). Fisheries landings generally declined in response to cumulative effects and often to a greater degree than would have been predicted based on individual climate effects, indicating possible synergies. Total biomass of fished and unfished functional groups displayed a decline, though unfished groups were affected less negatively. Some functional groups (e.g. pelagic and demersal invertebrates) were predicted to respond favourably under cumulative effects in some regions. The challenge of predicting climate change impacts must be met if we are to adapt and manage rapidly changing marine ecosystems in the 21st century.

The structure of plankton communities

1977 ◽  
Vol 280 (976) ◽  
pp. 485-534 ◽  
Keyword(s):  
Trophic Level ◽  
Size Structure ◽  
Food Limitation ◽  
Relative Size ◽  
Size Composition ◽  
Trophic Levels ◽  
Total Biomass ◽  
Size Dependent ◽  
First Feeding ◽  
Determining Modes

Interactions of herbivorous copepods with their phytoplankton food depend on the size composition of organisms in both trophic levels. A simulation model is used to analyse these size-dependent relations with the following conclusions. 1. Relative size structure of herbivores and their food is more important than total biomass of each trophic level in determining modes of transfer from plants to herbivores. In nearly all cases, in the model, food limitation affects reproduction or the first feeding stage of the nauplii. 2. No single factor emerges as predominant in determining the size structure of both populations. 3. The nature of predation on the herbivores is at least as important in determining both phytoplankton and herbivore size composition as physical or nutrient parameters. 4. The magnitude of the population of the larger herbivores such as Calanus , important as food for fish, depends on their coexistence with the smaller copepod species which control the smaller phytoplankton. 5. Stress on the system, if it affects adversely the smaller herbivores, can lead to the breakdown of the Calanus -diatom component. 6. Prediction of the population structure for both plants and herbivores may be a more attainable objective of theory and more practically important than prediction of total biomass at each trophic level.

scholarly journals Growth, Mortality and Exploitation Levels of Sphyraena sphyraena (Pisces: Sphyraenidae) and Apsilus fuscus (Pisces: Lutjanidae) in Ghanaian Waters

2021 ◽  
Vol 2 (1) ◽  
pp. 16-23
Author(s):  
Joseph Aggrey-Fynn ◽  
Divine Worlanyo Hotor
Keyword(s):  
Growth Parameters ◽  
Total Mortality ◽  
Growth Function ◽  
Frequency Data ◽  
Length Frequency ◽  
Fish Stocks ◽  
Von Bertalanffy Growth Function ◽  
Inshore Waters ◽  
The Mean ◽  
Length Frequency Data

Sphyraena sphyraena (Linnaeus, 1758) and Apsilus fuscus (Valenciennes, 1830) are commercially important fish species in Ghana. The stocks are exploited mainly by the artisanal and semi-industrial fisheries. Growth and mortality rates, and exploitation levels of the two stocks in inshore waters of Ghana were assessed as a contribution to fill the knowledge gap on the species. Samples were obtained from three landing sites along the coast of Ghana from February to July, 2017. Length-frequency data were used to estimate growth, mortality and exploitation ratios. The modal class for S. sphyraena was 37.0–39.9 cm total length (TL) and 34.0–35.9 cm TL for A. fuscus. The length and weight relationships established that growth in S. sphyraena was negative allometric, whereas that of A. fuscus was isometric. The estimated growth parameters from the length frequency data fitted with the von Bertalanffy growth function were asymptotic length (L∞) of 69.9 cm TL for S. sphyraena and 53.5 cm TL for A. fuscus. The growth constant (K) was calculated as 1.64 yr-1 for S. sphyraena and 0.50 yr-1 for A. fuscus. The mean length-at-first capture (Lc) was found to be lower than the mean length at sexual maturity (Lm) for both species. The sex ratio showed a dominance of females over males in S. sphyraena, and 1:1 for A. fuscus. The total mortality rate (Z) for S. sphyraena was more than for A. fuscus. The estimated natural mortality (M) was 1.88 yr-1 for S. sphyraena and 0.74 yr-1 for A. fuscus whilst fishing mortality (F) rate was 3.04 yr-1 for S. sphyraena and 0.93 yr-1 for A. fuscus. The exploitation ratio showed that both fish stocks were exploited over the optimum levels. The estimated population parameters of the species obtained from the study, therefore, might be useful for the sustainable management of the stocks.

scholarly journals Mesozooplankton biomass and temperature-enhanced grazing along a 110°E transect in the eastern Indian Ocean

2020 ◽  
Vol 649 ◽  
pp. 1-19 ◽  
Author(s):  
MR Landry ◽  
RR Hood ◽  
CH Davies
Keyword(s):  
Indian Ocean ◽  
Size Structure ◽  
Coupling Efficiency ◽  
Euphotic Zone ◽  
Dry Weight ◽  
Total Biomass ◽  
Low Latitude ◽  
Tropical Waters ◽  
Mesozooplankton Biomass ◽  
Lower Productivity

Low-latitude waters of the Indian Ocean are warming faster than other major oceans. Most models predict a zooplankton decline due to lower productivity, enhanced metabolism and phytoplankton size shifts that reduce trophic transfer efficiency. In May-June 2019, we investigated mesozooplankton biomass and grazing along the historic 110°E transect line from the International Indian Ocean Expedition (IIOE) of the 1960s. Twenty sampling stations from 39.5 to 11.5°S spanned latitudinal variability from temperate to tropical waters and a pronounced 14°C gradient in mean euphotic zone temperature. Although mesozooplankton size structure was similar along the transect, with smaller (<2 mm) size classes dominant, total biomass increased 3-fold (400 to 1500 mg dry weight m-2) from high to low latitude. More dramatically, gut-fluorescence estimates of grazing (total ingestion or % euphotic zone chl a consumed d-1) were 14- and 20-fold higher, respectively, in the low-latitude warmer waters. Biomass-normalized grazing rates varied more than 6-fold over the transect, showing a strong temperature relationship (r2 = 0.85) that exceeded the temperature effects on gut turnover and metabolic rates. Herbivory contributed more to satisfying zooplankton energetic requirements in low-chl a tropical waters than chl a-rich waters at higher latitude. Our unexpected results are inconsistent with trophic amplification of warming effects on phytoplankton to zooplankton, but might be explained by enhanced coupling efficiency via mixotrophy. Additional implications for selective herbivory and top-down grazing control underscore the need for rigorous field studies to understand relationships and validate assumptions about climate change effects on the food webs of tropical oceans.

scholarly journals Management effectiveness suggests a role in structuring herbivorous fish communities in Sinai marine protected areas, Gulf of Aqaba

2021 ◽  
Author(s):  
Khaled M. El-Haddad ◽  
Saad Z. Mohamed ◽  
Tarek A. Temraz ◽  
Abdel-Hamid A. Ali ◽  
Mohamed S. Abdel-Rahman
Keyword(s):  
Large Scale ◽  
Size Structure ◽  
Reef Fishes ◽  
Fish Populations ◽  
Herbivorous Fish ◽  
Gulf Of Aqaba ◽  
Management Approach ◽  
Numerical Density ◽  
Total Biomass ◽  
The Status

Herbivorous reef fishes are critically important for maintaining the health and resilience of coral reefs. In the Egyptian Gulf of Aqaba (GoA), many of these herbivores are important fishery targets and little is known about their population size structure and biomass patterns. Here, we conduct a large-scale (~250 km of coastline) assessment of the status of herbivorous fish populations along a fishing pressure gradient at 30 sites and eight regions in the GoA. These regions are subjected to three levels of fishing and protection, ranging from almost no fishing (No take, NT), and moderately fished (via Gear restriction, GR) to heavily fished (Open access, OA). We found that the NT fishery reserve was the most effective to maintain herbivorous fish size, biomass, and richness across all functional groups, though numerical density was not. Total herbivore biomass was 4.3 and 2.8 times higher on NT reefs and GR reefs, respectively than on OA reefs. Among GoA regions, only Ras Mohammed and Sharm El-Sheikh (unfished), and Nabq (fished) met the global mean herbivore biomass target of ~30 kg/500 m2. Our work also highlights three important results regarding the impacts of fishing and fisheries management on herbivorous fish populations: (i) size structure was heavily skewed toward smaller individuals, with fishes less than (20 cm) accounting for 81.1% of the population in heavily fished OA reefs vs. 52.8% at unfished NT reefs, (ii) biomass of larger herbivore individuals (>35 cm) accounting for less than 1% of the total biomass in OA reefs vs. 37% at NT reefs, and (iii) large-bodied target species, Cetoscarus bicolor, Naso unicorn, and Kyphosus spp., accounting for 15.9% of the total biomass at NT reefs on average, while they were virtually absent from OA reefs. Collectively, these findings suggest that many principal fisheries species in the central northern regions of the GoA have been overexploited, which in turn can lead to reef degradation. Therefore, there is an urgent need to develop a participatory management approach and enforce restrictions on destructive fishing gear in order to promote recovery of herbivore biomass.

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