Size Changes, Mortality, and Equilibrium Yields in an Exploited Stock of American Plaice (Hippoglossoides platessoides)

1969 ◽  
Vol 26 (5) ◽  
pp. 1205-1235 ◽  
Author(s):  
P. M. Powles
Keyword(s):  
Mesh Size ◽  
Food Competition ◽  
Mortality Factor ◽  
Otter Trawl ◽  
Small Fish ◽  
Large Fish ◽  
Age Composition ◽  
Instantaneous Rate ◽  
Factors Affecting ◽  
Ecological Dominance

Records from research surveys and commercial landings for American plaice from the Magdalen Shallows, or the southwestern Gulf of St. Lawrence, showed decreases in percentage of old, large fish and in catch per unit of effort from 1955 to 1962. The changes in age composition were clearly relatable to the fishery, which was mainly by otter trawl. Ricker models indicated that wastage of deck-exposed subcommercial plaice is currently a greater mortality factor than predation by cod. Increased landings in particular years were associated with successful year-classes. Other factors affecting landings were annual differences in fleet dispersal, which were related to movements of cod, a cohabiting species. No clear decrease or increase in absolute recruitment of plaice was demonstratable because quantitative comparisons of research surveys by different vessels using different gears and with different skippers, would be misleading.Mortality estimates of adult plaice by three methods showed agreement, indicating that instantaneous rate of natural mortality was between 0.09 and 0.13. The instantaneous rate of fishing for 1957–62 was 0.46. Increasing mesh-size would reduce cod catches and have little effect in conserving plaice, but marketing small fish would increase plaice landings. Voluntary release of small plaice promptly on capture would help maintain the stock, as would reduction in numbers of large cod, the main predator of small plaice. Increased numbers of small cod since 1959, as reported by other workers, could result in greater food competition with small plaice, effectively reinforcing the ecological dominance of cod over plaice.

Evaluation of coded wire tags for marking fingerling golden perch, Macquaria ambigua (Percichthyidae), and silver perch, Bidyanus bidyanus (Teraponidae)

1993 ◽  
Vol 44 (6) ◽  
pp. 817 ◽  
Author(s):  
BA Ingram
Keyword(s):  
Retention Rates ◽  
Small Fish ◽  
Large Fish ◽  
Recreational Fisheries ◽  
Factors Affecting ◽  
Operator Experience ◽  
Tag Retention ◽  
Total Length ◽  
Coded Wire Tags

Trials were conducted to evaluate coded wire tags for marking hatchery-produced golden perch and silver perch fingerlings prior to their release into the wild. Two size classes of fish were tagged: 'small' fish were 21-39 mm in total length and 'large' fish were 50-71 mm in total length. Tags were implanted into either the cheek muscle or the snout. Tagging rates were 200-548 fish h-1. Although tag retention in large cheek-tagged golden and silver perch was 100% after 30 days, rearing fish to this size was not practical. Retention rates for small cheek-tagged golden perch (94%) and silver perch (100%), the usual size of fingerlings when released to the wild, were considered to be sufficient for a tagging programme. Retention of tags in the snout was poor; only 6% of golden perch and 48% of silver perch retained tags after 30 days. Most cheek-implanted tags that were shed by fish during long-term tag-retention trials were lost in the first four months. With the exception of silver perch in one trial, which were infested by Ichthyophthirius multtfiliis, survival of tagged fish was 95-100% after 30 days. Factors affecting tag retention and survival of tagged fish, including fish size, tagging site and operator experience, are discussed. The results indicate that coded wire tags are a potential means of marking golden and silver perch fingerlings prior to stocking. Their use will assist fisheries managers in the assessment of the contribution of stocking programmes to commercial and recreational fisheries.

scholarly journals Pots as alternative and sustainable fishing gears in the Mediterranean Sea: an overview

2021 ◽  
Author(s):  
Andrea Petetta ◽  
Massimo Virgili ◽  
Stefano Guicciardi ◽  
Alessandro Lucchetti
Keyword(s):  
Mediterranean Sea ◽  
Early Stage ◽  
Spiny Lobster ◽  
Mesh Size ◽  
Octopus Vulgaris ◽  
Target Species ◽  
Factors Affecting ◽  
Fishing Gears ◽  
Pros And Cons ◽  
The Mediterranean

AbstractStock overexploitation, bycatch, discards and gear impacts on the environment are outstanding issues for Mediterranean fisheries. The adoption of alternative fishing gears is an appealing solution to ensure a more sustainable exploitation of resources. We discuss the pros and cons of pots as alternative gears by reviewing their main designs, spatial distribution and target species in the Mediterranean basin. We assessed the technical factors affecting the catch efficiency of the different pot designs for four target species: spiny lobster, Palinurus elephas; Norway lobster, Nephrops norvegicus; common octopus, Octopus vulgaris and pandalid shrimps, Plesionika spp. We found that pot volume is important to catch Octopus; mesh size to catch Nephrops and Plesionika; entrance surface to catch Octopus, Nephrops and Plesionika; pot shape/colour and entrance shape/position to catch Octopus and Plesionika; and bait type to catch Octopus and Nephrops. The literature review shows that pot fisheries have several considerable advantages over conventional gears, especially in terms of discards, bycatch, seabed impacts (particularly compared with bottom trawls and passive set nets), size and species selectivity, gear depredation, catch quality and gear cost, besides saving time and labour. Disadvantages hampering their wider diffusion include ghost fishing, a low catch of finfish species, the narrow range of species targeted by each pot design and the current early stage of research. These data make a clear case for using pots as alternative gears to traditional ones in the Mediterranean Sea in some areas and seasons to catch certain target species.

scholarly journals Two methods of assessing the mortality factors affecting the larvae and pupae of Cameraria ohridella in the leaves of Aesculus hippocastanum in Switzerland and Bulgaria

2007 ◽  
Vol 97 (5) ◽  
pp. 445-453 ◽  
Author(s):  
S. Girardoz ◽  
R. Tomov ◽  
R. Eschen ◽  
D.L.J. Quicke ◽  
M. Kenis
Keyword(s):  
Leaf Senescence ◽  
Sampling Method ◽  
Plant Defence ◽  
Leaf Miner ◽  
Mortality Factor ◽  
Horse Chestnut ◽  
Mortality Factors ◽  
Grab Sampling ◽  
Defence Reaction ◽  
Factors Affecting

AbstractThe horse-chestnut leaf miner, Cameraria ohridella, is an invasive alien species defoliating horse-chestnut, a popular ornamental tree in Europe. This paper presents quantitative data on mortality factors affecting larvae and pupae of the leaf miner in Switzerland and Bulgaria, both in urban and forest environments. Two sampling methods were used and compared: a cohort method, consisting of the surveying of pre-selected mines throughout their development, and a grab sampling method, consisting of single sets of leaves collected and dissected at regular intervals. The total mortality per generation varied between 14 and 99%. Mortality was caused by a variety of factors, including parasitism, host feeding, predation by birds and arthropods, plant defence reaction, leaf senescence, intra-specific competition and inter-specific competition with a fungal disease. Significant interactions were found between mortality factors and sampling methods, countries, environments and generation. No mortality factor was dominant throughout the sites, generations and methods tested. Plant defence reactions constituted the main mortality factor for the first two larval stages, whereas predation by birds and arthropods and parasitism were more important in older larvae and pupae. Mortality caused by leaf senescence was often the dominant mortality factor in the last annual generation. The cohort method detected higher mortality rates than the grab sampling method. In particular, mortality by plant defence reaction and leaf senescence were better assessed using the cohort method, which is, therefore, recommended for life table studies on leaf miners.

scholarly journals Factors affecting rule compliance with mesh size regulations in the Baltic cod trawl fishery

2007 ◽  
Vol 64 (8) ◽  
pp. 1603-1606 ◽  
Author(s):  
Petri Suuronen ◽  
Vesa Tschernij ◽  
Pekka Jounela ◽  
Daniel Valentinsson ◽  
P-O. Larsson
Keyword(s):  
Gadus Morhua ◽  
Management Practice ◽  
Mesh Size ◽  
Factors Affecting ◽  
Trawl Fishery ◽  
Management Measures ◽  
Gradual Introduction ◽  
Minimum Landing Size ◽  
The Baltic ◽  
Baltic Cod

Abstract Suuronen, P., Tschernij, V., Jounela, P., Valentinsson, D., and Larsson, P-O. 2007. Factors affecting rule compiance with mesh size regulations in the Baltic cod trawl fishery. – ICES Journal of Marine Science, 64: 1603–1606. In this study, we evaluate the efficiency and applicability of a series of gear-based management measures, enforced since 1990, whose purpose was to improve size selectivity in the trawl fishery for Baltic cod (Gadus morhua). In general, our study revealed that these measures had no marked effect on the capture and discard of young cod. Legal and illegal manipulation of selective codends was widespread. The adoption of a codend design that offered a modest increase in selectivity, but had a good match with the legislated minimum landing size (MLS), led to greater compliance, demonstrating that a mismatch between MLS and selectivity should be avoided. It was also obvious that, generally, the fishing industry did not tolerate large short-term losses. Our evaluation is that overly ambitious rules will be circumvented, and frequent and incoherent changes in the regulations represent bad management practice. A gradual introduction of restrictions and participation by fishers in the decision-making process will increase compliance.

Pectoral fin locomotion in the striped surfperch. I. Kinematic effects of swimming speed and body size

1996 ◽  
Vol 199 (10) ◽  
pp. 2235-2242 ◽  
Author(s):  
E Drucker ◽  
J Jensen
Keyword(s):  
Body Size ◽  
Swimming Speed ◽  
Beat Frequency ◽  
Limited Range ◽  
The Body ◽  
Small Fish ◽  
Large Fish ◽  
Pectoral Fin ◽  
Transition Speed ◽  
Speed Up

Swimming trials at increasing velocity were used to determine the effects of steady swimming speed on pectoral fin kinematics for an ontogenetic series of striped surfperch Embiotoca lateralis, ranging from 6 to 23 cm in standard length (SL). The fin stroke cycle consisted of a propulsive period, the duration of fin abduction and adduction, and a 'refractory' period, during which the fin remained adducted against the body. Pectoral fin-beat frequency (fp) measured as the inverse of the entire stride period, as in past studies, increased curvilinearly with speed. Frequency, calculated as the reciprocal of the propulsive period alone, increased linearly with speed, as shown previously for tail-beat frequency of fishes employing axial undulation. Fin-beat amplitude, measured as the vertical excursion of the pectoral fin tip during abduction, increased over a limited range of low speeds before reaching a plateau at 0.35­0.40 SL. Pectoral fin locomotion was supplemented by intermittent caudal fin undulation as swimming speed increased. At the pectoral­caudal gait transition speed (Up-c), frequency and amplitude attained maxima, suggesting that the fin musculature reached a physiological limit. The effects of body size on swimming kinematics differed according to the method used for expressing speed. At a given absolute speed, small fish used higher stride frequencies and increased frequency at a faster rate than large fish. In contrast, the relationship between fp and length-specific speed (SL s-1) had a greater slope for large fish and crossed that for small fish at high speeds. We recommend that comparisons across size be made using speeds expressed as a percentage of Up-c, at which kinematic variables influencing thrust are size-independent.

Cardiac output determinations by the dye-dilution method in Squalus acanthias

1965 ◽  
Vol 209 (4) ◽  
pp. 723-726 ◽  
Author(s):  
H. Victor Murdaugh ◽  
Eugene D. Robin ◽  
J. Eugene Millen ◽  
William F. Drewry
Keyword(s):  
Cardiac Output ◽  
Cardiac Index ◽  
Squalus Acanthias ◽  
Physiological Status ◽  
Dilution Method ◽  
Small Fish ◽  
Large Fish ◽  
Dilution Technique ◽  
Dye Dilution ◽  
Cardiac Output Measurements

A dye-dilution technique has been adapted for the measurement of cardiac output in the elasmobranch, Squalus acanthias. Cardiac output averaged 1.60 ± 1.00 liter/kg per hr in 26 fish. Small fish showed a relatively high cardiac index (liters/kg per hr) as compared with large fish. The use of this technique permits sequential cardiac output measurements with the maintenance of an intact physiological status. This technique should permit quantitation of exchange of a variety of substances across the gill membranes.

scholarly journals The relation between concentrations of ovarian trace elements and the body size of Atlantic cod Gadus morhua

2008 ◽  
Vol 65 (7) ◽  
pp. 1191-1197 ◽  
Author(s):  
A. Bang ◽  
P. Grønkjær ◽  
B. Lorenzen
Keyword(s):  
Trace Elements ◽  
Body Size ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
The Body ◽  
Small Fish ◽  
Female Size ◽  
Large Fish ◽  
Size Category ◽  
Linear Discriminant

Abstract Bang, A., Grønkjær, P., and Lorenzen, B. 2008. The relation between concentrations of ovarian trace elements and the body size of Atlantic cod Gadus morhua. – ICES Journal of Marine Science, 65: 1191–1197. Trace metals in the ovaries of fish are transferred from the female via the yolk to the offspring, which makes the early life stages susceptible to deleterious effects of potentially toxic elements contained in the ovaries. Here, the concentrations of 13 elements from the ovaries of 133 ripe female North Sea cod Gadus morhua weighing 0.2–18 kg were correlated with female size, accounting for differences in maturity and condition. Most elements were negatively correlated with the size variables weight, length and, especially, ovarian dry weight. Further, they were negatively correlated with maturity and condition. Many of the trace elements showed true size-dependence, but the correlations were generally weak. A linear discriminant analysis separated “small” and “large” fish at a length of 85 cm based on concentrations of Co, Mn, Se, and Zn, and correctly assigned 78 of 102 small fish and 23 of 31 large fish to their respective size category. This corresponds to an overall classification success of 75.9%. The results suggest that embryos and early larvae from small females are exposed to higher levels of potentially harmful metals. If the differences in trace element concentration influence survival success, this will add to the negative effects of size distribution truncation and declines in size-at-maturity experienced by many populations of cod.

Variations in sex, length and age compositions of commercial catches of Platycephalus fuscus (Pisces : Platycephalidae) in New South Wales, Australia

2002 ◽  
Vol 53 (7) ◽  
pp. 1091 ◽  
Author(s):  
C. A. Gray ◽  
V. J. Gale ◽  
S. L. Stringfellow ◽  
L. P. Raines
Keyword(s):  
Average Length ◽  
New South ◽  
New South Wales ◽  
Total Mortality ◽  
Mesh Size ◽  
Growth Zone ◽  
Male Fish ◽  
Age Composition ◽  
South Wales ◽  
By Catch

Commercial landings of dusky flathead (Platycephalus fuscus) from four estuaries in New South Wales (NSW), Australia, were sampled for data on sex, length and age composition between February and July each year for 2–3 years between 1995 and 1997. Landings primarily contained female fish, ranging from 55% to 93% by number for different estuaries. Flathead sampled in commercial catches ranged from 30 cm to 96 cm total length (TL), but the majority were 33–50 cm TL. Fish >40 cm TL were primarily female and male fish >45 cm TL were uncommon. The length composition of catches differed between gillnets of different mesh sizes, with the average length of fish being least in the smallest allowed mesh size of 70 mm. Fish were aged by otolith interpretation and the analysis of marginal increments indicated that one opaque and one translucent growth zone was formed each year; the opaque zone being deposited in June–August (winter) and first observed in September–October (spring). Commercial landings included fish aged 2–11+ years, but fish aged 2–4+ years dominated landings in all estuaries. The total mortality of dusky flathead in each estuary was estimated by catch curve analysis and was relatively high, ranging from 0.45 to 1.64. The data indicate that dusky flathead may be heavily exploited in NSW.

Seasonal, Grazing Site and Fish Size Effects on Patterns of Algal Consumption by the Herbivorous Fish, Siganus rivulatus, at Mikhmoret (Mediterranean, Israel)

1993 ◽  
Vol 27 (7-8) ◽  
pp. 413-419 ◽  
Author(s):  
B. Lundberg ◽  
Y. Lipkin
Keyword(s):  
Late Summer ◽  
Food Composition ◽  
Mediterranean Coast ◽  
Medium Size ◽  
Limited Area ◽  
Small Fish ◽  
Large Fish ◽  
Food Species ◽  
The Difference ◽  
Siganus Rivulatus

Siqanus rivulatus, a successful herbivorous immigrant fish from the Red Sea, consumes along the Israeli east Mediterranean coast a wide variety of algae. Only four of them composed about a half of the bulk of its food, and only twelve, about 80% of it. Seasonal changes in quantitative representation of different algae in the food followed several patterns. Most algae were taken throughout the year. Proportions in the food of some algae fluctuated only slightly during the year, proportions of others were very great during short periods and much smaller during the rest of the year. Polvsiphonia is an example for the former, Ulva and Spatoglossum, for the latter. Among the latter, Ulva dominates the food contents during the end of winter and spring; Spatoglossum, during the late summer. As shown previously, s. rivulatus prefers certain algae as food. Nevertheless, food composition in fish captured at inshore sites differed from that of fish captured offshore. This reflects, to a certain extent, the difference in vegetation between these sites, and the fact that the fish tend to graze in a rather limited area at a time. Small and large fish take different algal food species. Unexpectedly, small fish clearly preferred some large and robust algae, consuming them in much greater proportions than bigger fish. Also unexpectedly, medium size fish showed preferences and avoidances of their own in regard to the consumption of certain algae, and not merely occupied an intermediate position between small and large fish.

Size and Density Dependent Mating Tactics in the Simultaneously Hermaphroditic Seabass Serranus Subligarius (Cope, 1870)

Behaviour ◽  
1997 ◽  
Vol 134 (7-8) ◽  
pp. 563-594 ◽  
Author(s):  
Ann S. Oliver
Keyword(s):  
Mating Behavior ◽  
Evolutionarily Stable Strategy ◽  
Small Fish ◽  
Large Fish ◽  
Mating Tactics ◽  
Spawning Period ◽  
Female Pair ◽  
Fish Trade ◽  
Evolutionarily Stable ◽  
Daily Spawning

AbstractThis study examines factors within the mating system of Serranus subligarius (belted sandfish) that are likely to maintain simultaneous hermaphroditism as an evolutionarily stable strategy in a highly mobile, high density species. I focus on changes in mating behavior with size. Mating behavior was observed underwater in the northeastern Gulf of Mexico at St. Andrew Bay State Park. Every hermaphrodite can spawn in three roles over the course of the daily spawning period: female pair spawn, male pair spawn, and male streak spawn. Pair spawning fish trade eggs, taking turns fertilizing one another's eggs. Egg trading is not symmetrical; the smaller fish in a pair spawns more often in the female role than the larger fish. Overall, small fish ( 70 mm SL) pair spawn more frequently as females, while large fish ( 80 mm SL) pair spawn more often as males. A size advantage appears to exist for male function. However, large fish usually release at least one egg parcel per spawning

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