Maximum Attainable Length Research Articles

The demersal fish composition and catch per unit effort of mini bottom trawl at the coast of Demak Regency Central Java

Demak is a coastal area on the North Coast of Java with a large enough potential for demersal fish resources. This research aimed to determine the composition, the length and weight distribution, and catch per unit effort (CPUE) of demersal fish caught using mini bottom trawl at the north coast of Demak Regency. The research was carried out in October-December 2020 by observation of ten trips of mini bottom trawl fishing. Each fish captured was then grouped by type, identified, and measured its length and weight. The result showed that 38 species consist of 31 fishes, four mollusks, and three crustaceans. The fish captured dominated by pony fish (Leiognathus equulus) as much as 31.23% and largehead hairtail (Trichiurus lepturus) of 23.52%. The catch per unit effort (CPUE) average of mini bottom trawl was 44.77 kg/trip. Mainly fish (more than 95%) caught in small size compared it’s the maximum attainable length (L-max), with all the weight ranges from 0.3 to 520 g and more than 98% sized 0.3-80 g. Mini bottom trawl catches many types of fish and small size; therefore, mini bottom trawl is classified as a type of fishing gear with a very low selectivity level.

Life-history characteristics of the endangered Aristotle’s catfish (Silurus aristotelisGarman, 1890), Lake Pamvotis, north-western Greece

The life history characteristics of Aristotle’s catfish, Silurus aristotelis (Agassiz 1856) were studied in Lake Pamvotis (northwestern Greece). Samples were collected on a monthly basis using gillnets, trammel-nets and traps. Total lengths ranged from 11.1 to 36.7 cm. Sex ratio was biased toward females (F : M = 1.8 : 1) and was statistically different from unity (χ2 = 46.94, P < 0.001). Spawning is from April to June. The relationship between total length and total weight showed positive allometric growth for males (TW = 0.0035 × TL3.21, r2 = 0.93, n = 198, P < 0.001) and females (TW = 0.0066 × TL3.02, r2 = 0.95, n = 363, P < 0.001). Age was determined on the annual growth marks formed on the spine of the pectoral fin. Based on cross-section readings of the spine, lifespan of the Aristotle’s catfish was 5 years. Age classes 1 and 2 dominated the catches (39.1 and 40.0% of the total sample, respectively). Back-calculated lengths at age showed a rapid increase in fish size during the first year of life, reaching 61.1% of maximum attainable length, and a declining growth rate thereafter. Growth parameters were calculated as L∞ = 36.12 cm, K = 0.37 year−1, t0 = −0.76 year based on the observed lengths at age and as L∞ = 28.19 cm, K = 0.53 year−1, t0 = −0.62 year based on the back-calculated lengths at age. It seems that some of the life history traits (longevity, growth pattern, reproductive period) are influenced significantly by adverse effects of pollution and eutrophication on the lacustrine ecosystem.

Growth in the bivalve Macoma balthica from its northern to its southern distribution limit: a discontinuity in North Europe because of genetic adaptations in Arctic populations?

The hypothesis was tested that towards a species limit of distribution its performance, such as growth or fitness, decreases. To this end, latitudinal changes in growth, maximum attainable length and genetic constitution were assessed for the Baltic clam, Macoma balthica (L.), at stations ranging from the most southern distribution limit (France) to its most north-eastern limit in the Arctic Pechora Sea (North Russia). Growth was analyzed by means of growth-rings on the shells, the genetic constitution by electrophoretic isoenzyme analysis. Growth patterns and the genetic constitution of populations from West Europe, North Europe and the White Sea were similar, whereas the populations from the Pechora Sea are distinct from the other populations. The performance of clams in the Pechora Sea populations, with a relatively low annual growth but high maximum length, was, in contrast to the hypothesis, not decreased. It is concluded that the Pechora Sea populations form a separate group, genetically different from other European populations and adapted to the Arctic conditions.

Growth rates and body condition factors of Alligator mississippiensis in coastal Louisiana wetlands: A comparison of wild and farm-released juveniles

1. 1. Growth rates and body condition factors for native wild and captive-raised juvenile alligators ( Alligator mississippiensis) that had been released to the wild were studied using tag-recapture methods for 274 alligators over a 4-year period. Alligators were grouped by sex, size class, source (farm-released vs native wild) and as to whether they had overwintered or not. 2. 2. In most groups, the farm-released alligators grew significantly better than wild alligators matched for sex and size; in the remaining groups the post-release alligators grew as well as their counterparts, though not better. 3. 3. Overwintering tended to slow growth rates in both groups, but farm-released alligators still demonstrated superior growth over native wild alligators even after overwintering. 4. 4. Males tended to grow faster than females, though this trend was not always significantly greater. In no matched group did females grow faster than males. 5. 5. Growth rates diminished with increasing size in native wild alligators (smaller alligators grew faster), but growth rates of farm-released alligators remained accelerated even at the larger size classes. 6. 6. Growth curves were constructed using known recapture data with three growth models (von Bertlanffy, Gompertz and logistic); the calculated maximum attainable length and growth parameters were significantly larger ( P < 0.01) for farm-released alligators than wild using all three models. 7. 7. Body condition factors were not different in captive-raised post-released alligators than native wild alligators.

Life history of the bowhead whale, Balaena mysticetus (Mammalia: Cetacea)

This paper synthesizes data collected from bowhead whales (Balaena mysticetus) landed by Alaskan Eskimos between 1973 and 1982. From these data, and from the literature, length at birth has been estimated to be 4‐4.5 m, length at one year to be 8‐2 m, length at sexual maturity to be 14 m in females, and maximum length to be 20 m. Sexual activity, possibly mating, has been observed in March through May and the length of gestation is estimated to be 13 months. The calving period appears to extend from March through August, with the peak in births occurring in May. Lactation may extend for one year. Evidence has been provided for a pregnancy rate (percentage pregnant in mature female catch) of 015 and it has been suggested that calving occurs every three to six years. Gross annual reproductive rate (based on calf sightings) is estimated to be at least 3–6%. Sources of mortality are discussed. The sex ratio of animals taken by Eskimos is 0.83: 1.00 (females to males) and is not significantly different from unity.SummaryThe conclusions drawn in each of the preceding sections are likely to be re‐evaluated as more information becomes available. Still, it is suggested that the length at birth is 4–4.5 m, length at one year is 8.2 m, length at sexual maturity is 14 m in females, and the maximum attainable length is 20 m. Conception is most likely to occur in late winter while the whales congregate in Bering Sea polynyas, whereas the peak in calving appears to occur in May. Consequently, it has been hypothesized that the gestation time is greater than one year, but less than two. By analogy with other right whales and sparse data collected, the duration of lactation is assumed to be one year, although this is arguable. The pregnancy rate of mature females, calculated from ovarian data, is 0.15, projecting a calving interval of approximately seven years. The gross annual reproductive rate generated from field data is 3.6–12.4%. The sex ratio of the harvested animals is 0.83: 1.0, and it is assumed that this does not reflect the whole population. Whatever changes are yet to be made in the understanding of the bow‐head life history, all of the traits delineated are consistent with those predicted for slowly reproducing animals, the quintessential K‐strategist.We are most grateful to the scores of field biologists who have helped us count whales and sample those landed by the Eskimos, and who have contributed ideas and enthusiasm. In addition, we thank R. Tarpley for information on ovaries collected in 1982, J. Breiwick for running several sex ratio estimates, and H. Marsh for her generous assistance with the ovarian histology. Under contract to us R. Davis and W. Koski of L.G.L., environmental research associates, provided the photogrammetric measurements. An earlier, less complete version of our paper was submitted in 1982 as an unpublished report (document SC/34/PS1) to the International Whaling Commission, resulting in many valuable comments from members of the Scientific Committee. P. Best, D. Chapman, and an anonymous reviewer substantially improved the manuscript. Finally, we thank the people of Barrow, Point Hope, Wainwright, Gambell, Savoonga, and Kaktovik for their patience and assistance. Without their support this research would not have been possible.

Age and Growth of Spotted Bass (Micropterus punctulatus) in Lake Fort Smith, Arkansas

Abstract Age and growth data are presented on 380 spotted bass, Micropterus punctulatus, collected between June 1970 and July 1972 from Lake Fort Smith, Arkansas. Annuli were formed from late May through July; young spotted bass formed annuli earlier and during a shorter period of time than older individuals. Growth of males and females was similar and generally slower than that reported from other waters. The most active period of annual growth was initiated later and was of shorter duration in older fish. Growth, according to von Bertalanffy's equation, was best expressed as Lt = 350 [1 - e-0.511(t-0.330)], where L is total length in mm and t is age in yr. Maximum attainable length (L∞) was calculated to be 350 mm and 6.2 yr would be required to reach 95% of this length.

Measurements of Friction in a Pipe for Subsonic and Supersonic Flow of Air

Abstract The apparent friction coefficient was determined experimentally for the flow of air through smooth pipes at subsonic and supersonic velocities. Values of the Mach number ranged from 0.27 to 3.87, and of Reynolds number from 1 × 105 to 8.7 × 105. In supersonic flow the results were found to be strongly influenced by the presence of oblique shocks formed at the junction of nozzle and pipe. The effect of these shocks on the coefficient of friction was determined. Nozzle forms were devised which eliminated the shocks and their effects. It was found that at distances from the pipe inlet greater than 50 diam the apparent coefficient of friction for compressible flow at Mach numbers greater or less than 1 is approximately equal, for equal Reynolds numbers, to the coefficient of friction for incompressible flow with completely developed boundary layer. Mach numbers greater than 1 are rarely maintained for lengths greater than 50 diam. For attainable lengths, the coefficient of friction is a function of the ratio of length to diameter and the Reynolds number, with the Mach number at entrance determining the maximum attainable length.