Dynamics of bigeye (Thunnus obesus) and yellowfin (T. albacares) tuna in Hawaii’s pelagic fisheries: analysis of tagging data with a bulk transfer model incorporating size-specific attrition

Tag release and recapture data of bigeye (Thunnus obesus) and yellowfin tuna (T. albacares) from the Hawaii Tuna Tagging Project (HTTP) were analyzed with a bulk transfer model incorporating size-specific attrition to infer population dynamics and transfer rates between various fishery components. For both species, the transfer rate estimates from the offshore handline fishery areas to the longline fishery area were higher than the estimates of transfer from those same areas into the inshore fishery areas. Natural and fishing mortality rates were estimated over three size classes: yellowfin 20–45, 46–55, and ≥56 cm and bigeye 29–55, 56–70, and ≥71 cm. For both species, the estimates of natural mortality were highest in the smallest size class. For bigeye tuna, the estimates decreased with increasing size and for yellowfin tuna there was a slight increase in the largest size class. In the Cross Seamount fishery, the fishing mortality rate of bigeye tuna was similar for all three size classes and represented roughly 12% of the gross attrition rate (includes fishing and natural mortality and emigration rates). For yellowfin tuna, fishing mortality ranged between 7% and 30%, the highest being in the medium size class. For both species, the overall attrition rate from the entire fishery area was nearly the same. However, in the specific case of the Cross Seamount fishery, the attrition rate for yellowfin tuna was roughly twice that for bigeye. This result indicates that bigeye tuna are more resident at the Seamount than yellowfin tuna, and larger bigeye tunas tend to reside longer than smaller individuals. This may result in larger fish being more vulnerable to capture in the Seamount fishery. The relatively low level of exchange between the Sea-mount and the inshore and longline fisheries suggests that the fishing activity at the Seamount need not be of great management concern for either species. However, given that the current exploitation rates are considered moderate (10–30%), and that Seamount aggregations of yellowfin and bigeye tuna are highly vulnerable to low-cost gear types, it is recommended that further increases in fishing effort for these species be monitored at Cross Seamount.

Bycatch of lined seahorses (Hippocampus erectus) in a Gulf of Mexico shrimp trawl fishery

Bycatch studies have largely ignored population level effects on fish species of little commercial interest. Here we analyze bycatch of the lined seahorse (Hippocampus erectus) in the bait-shrimp trawl fishery in Hernando Beach, Florida, providing the first fisheries data for this species. Based on catch per unit of effort (CPUE), size, sex, and reproductive status of trawled H. erectus, 1) approximately 72,000 seahorses were caught annually by this fleet, from a population of unknown size, 2) trawling affected population cohorts differentially because of temporal and spatial variation in CPUE and population size, and 3) a greater proportion of females than males was removed in trawling. Our findings suggest that trawling may affect seahorse populations through direct mortality, social disruption, and habitat damage. However, the lack of specific abundance or catchability estimates for H. erectus means that the precise impact of trawling on this fish remains uncertain. This paper focuses attention on the need for research and monitoring of small fishes that are caught incidentally in nonselective gear.

Age, growth, and mortality of the Mayan cichlid (Cichlasoma urophthalmus) from the southeastern Everglades

Mayan cichlids (Cichlasoma urophthalmus) were collected monthly from March 1996 to October 1997 with hook-and-line gear at Taylor River, Florida, an area within the Crocodile Sanctuary of Everglades National Park, where human activities such as fishing are prohibited. Fish were aged by examining thin-sectioned otoliths, and past size-at-age information was generated by using back-calculation techniques. Marginal increment analysis showed that opaque growth zones were annuli deposited between January and May. The size of age-1 fish was estimated to be 33–66 mm standard length (mean=45.5 mm) and was supported by monthly length-frequency data of young-of-year fish collected with drop traps over a seven-year period. Mayan cichlids up to seven years old were observed. Male cichlids grew slower but achieved a larger size than females. Growth was asymptotic and was modeled by the von Bertalanffy growth equation Lt=263.6(1–exp[–0.166(t–0.001)]) for males (r2=0.82, n=581) and Lt=215.6 (1–exp[–0.197(t–0.058)]) for females (r2= 0.77, n=639). Separate estimates of total annual mortality were relatively consistent (0.44–0.60) and indicated moderate mortality at higher age classes, even in the absence of fishing mortality. Our data indicated that Mayan cichlids grow slower and live longer in Florida than previously reported from native Mexican habitats. Because the growth of Mayan cichlids in Florida periodically slowed and thus produced visible annuli, it may be possible to age introduced populations of other subtropical and tropical cichlids in a similar way.

Estimated ages of red porgy (Pagrus pagrus) from fishery-dependent and fishery-independent data and a comparison of growth parameters

The red porgy, Pagrus pagrus, is an important reef fish in several offshore fisheries along the southeastern United States. We examined samples from North Carolina through southeast Florida from recreational (headboat) and commercial (hook and line) fisheries, as well as samples from a fishery-independent source. Red porgy attain a maximum age of at least 18 years and 733 mm total length. The weight-length relationship is represented by the ln-ln transformed equation: W = 8.85 × 10–6(L)3.06, where W = whole weight in grams, and L = total length in mm. The von Bertalanffy growth equation fitted to the most recent, back-calculated lengths from all the samples is Lt = 644(1 – e –0.15(t + 0.76)). Our study revealed a difference in mean length at age of red porgy from the three sources. Red porgy in fishery-independent collections were smaller at age than specimens examined from fishery-dependent sources. The difference in length-at-age may be related to gear selectivity and have important consequences in the assessment of fish stocks.

Avaliação dos consumos de materiais estratégicos para a conservação dos engenhos de pesca artesanal de Moçambique e Estudos de constituiçāo tipologia e distribuiçāo de alguns engenhos de pesca artesanal de Moçambique

This technical report comprises two different studies in terms of their conclusions, but based on the same field surveys: “Yearly consumption evaluation of the strategic materials for the artisanal fisheries of Mozambique” and “Constitution, typology and distribution studies of the Mozambican artisanal fishing gears”. In the first of the above studies, the amount of the materials found in each gear, the number of such gears and the wear factor “r” are subject to a computed data processing, producing the following outputs: list of materials demanded in each Mozambican fishing relevant province; list of materials demanded in the whole Mozambican territory. In the second study the observed gears constitutions are analysed and differences and similitudes among them are searched. The details of maneuver and productivity are referred as well. Attention is drawn to the fact that observations did not take place on the whole Mozambican territory, even not in the most representative but in some considerably important fishing centers with reasonable safety and connection facilities. About the first study, when it was not possible to reach such considerably important centers the determination of the approximate picture of them has been achieved by verbal information of people knowing them very well and by the sources referred here in after. Concerning the second study inferences have not been made. Although a limited number of samples has been collected, the accuracy of it has been checked by inquiry. Speculations have been developed only on observed cases. The surveys have been made by a team, assigned by the directors of UD-PPE and Equipesca, under author’s coordination.

Towing resistance of ottar [i.e. otter] trawls used for shrimps from small mechanised boats

Attempts have been made to determine the towing resistance of the shrimp otter trawls operated from small trawlers off Cochin and the actual resistance on the warps for eight different boats working under the normal fishing conditions have been measured. Engine Horse Power utilised for towing the gear at normal speed and fishing conditions has also been estimated.

Pawn [i.e. prawn] fishery in Gujarat location of new prawn grounds off Veraval

Details about the three departmental vessels, Gulf shrimp, Indian Salmon and Silver Pomfret and gear in the exploratory fishing off Veraval coast are reported. Potential prawn fishing grounds have been located by their operation in section 20-70, 21-69 and 22-69 in the cruises conducted in October, 1962. Observation regarding suitability of gear and composition of catch are given. The possibility of better prawn grounds occurring in areas deeper than the present grounds is indicated.

Prawn fishing by M.F.V. Jheenga in Bombay waters

The design and construction of the motor fishing vessel Jheenga of the Deep Sea Fishing Station of the Government of India, Bombay, the areas covered and the gear used by her in 1959-63 are described. The prawn catches in relation to the total catches, and their catch rates in different months in area 18-72 in Bombay region which was fished continuously during the five years period have been studied with a view to ascertaining their seasonal abundance. The results indicate the availability of the prawns in the region for the major part of the year from March to October-November. High catches with high catch rates forming high percentage of their abundance in total catches are obtained in July to October.

Trends in development in the prawn fishing technique in India: a review

The paper provides some background information about the developments in the prawn fishing technique. The important indigenous gear for prawns are the filtering type nets like the stake nets, boat seines and beach seines with bag. The only indigenous net, which can be compared in design with the modern bottom trawling gear, is the "Thuri Valai" of the Madras Coast. Prawns have also been reported from the catches of gill nets and cast nets. Dredges and beam trawls are simplest among the dragged gear. Even though several earlier attempts were made with the beam trawl, in 1959 season a detailed experiment was made to study the fishing features of this gear. The subsequent experiments conducted were for comparison with otter trawl, towing of 2 beam trawls one behind the other and the use of tickler chain. The initial experiments with otter trawls were mainly directed towards operational aspects. The experiments were to evaluate the effectiveness of fully mechanised and partially mechanised operation, the effect of extra buoyancy of floats and the use of tickler chain. Subsequent developments had been on the structure and design of prawn trawling gear. Effect of long wings and sweeps were tested. Catches of nylon and cotton nets were compared. The sizes of meshes of the cod-end have also been increased.

The Central Institute of Fisheries Technology, Ernakulam

In appreciation of the pressing need for coordinated research in various aspects of fishery technology and for the overall development of fisheries industries in India, the Ministry of Food and Agriculture had decided to set up the Central Institute of Fisheries Technology. The Institute was established in 1957 at Cochin (Ernakulam). The research work at the Institute including its sub-stations and units is carried out in two wings: Craft and Gear Wing and Processing Wing. The third unit, the Extension Information and Statistics Wing, renders a service by functioning as a liaison between the research laboratories and the industry.

Operatives training programmes in India

During the last few years great changes have taken place in the fishing industry as a result of which production of fish in the world has increased enormously. From an insignificant trade employing tools and methods of primitive nature, fishing in many countries has become an important industry utilizing complex modern vessels equipped with electronic equipment and operating in the high seas with highly mechanized fishing gear.

Preliminary observations on the effect of a. c. current on Catla catla and Ophicephalus punctatus

In order to evolve suitable electrical fishing gear for inland waters, preliminary experiments have been conducted to observe effect of a. c. currents on Catla catla at voltages of 30, 90 and 120, pH 7.3 and 8.4, temperature 48°F, 78°F and 105°F, distance between electrodes 25 cm, 50 cm and 75 cm, size range of fish 100 mm, to 235 mm. Apparatus used was a 5 kw; a. c. 60 cycles generator with resistance control. Larger sizes of fish were more prone to electric shock. Higher temperature increases the intensity of the shock, while variation of pH between 7.3 to 8.4 did not materially affect the intensity of the shock. Fishing with a mixed population of Catla catla and Ophicephalus punctatus gave a greater percentage of mortality for the latter.

Experiments in fishing with shrimp trawls: on the standardisation of tickler chain

The communication deals with the results of experiments conducted off Gujarat coast for the standardisation of "Tickler chain" for shrimp trawls. Of the short link chains made of 3.2 mm, 4.8 mm and 6.2 mm rods the second was observed to increase the yield of shrimp in the net and without in any way adversely affecting the performance of the gear. The chains used had no influence on the fish catch.

Spiny lobsters of Ceylon

Spiny lobsters of the family Palinuridae are known to exist in parts of Asia such as India, Japan, Indonesia and Malaya. In Ceylon spiny lobsters are caught chiefly by a primitive type of gear designed to catch these species and incidentally by nets set to catch fish. The limitations of these types of gear and the results of experimental fishing in Ceylon with different designs of lobster traps have been discussed earlier. As a result of these experiments a very effective trap for capturing spiny lobsters was developed and it was shown that spiny lobsters were present in large quantities (De Bruin 1960). This created great interest among skin-divers who found lobster fishing very remunerative.

On the troll line investigations off Cochin during five fishing seasons. Pt. 1. Investigations during 1960-61 and 1961-62 seasons

There is apparently great scope for improvement of the design and operational aspects of the gear particularly for the effective exploitation of seasonal fisheries like that of seer, tuna, barracuda etc. In order to evolve improved, yet cheap trolling gear regular investigations were undertaken by the Craft & Gear Wing of the Central Institute of Fisheries Technology, off Cochin for five fishing seasons and the results of these studies are incorporated in this paper.