scholarly journals Underwater observations of seal–fishery interactions and the effectiveness of an exclusion device in reducing bycatch in a midwater trawl fishery

2016 ◽  
Vol 73 (3) ◽  
pp. 436-444 ◽  
Author(s):  
Jeremy M. Lyle ◽  
Simon T. Willcox ◽  
Klaas Hartmann
Keyword(s):  
Mortality Rates ◽  
Video Monitoring ◽  
Underwater Video ◽  
Fishing Activity ◽  
Midwater Trawl ◽  
Trawl Fishery ◽  
Space And Time ◽  
Operational Factor ◽  
Fishery Interactions ◽  
Pelagic Fishery

Interactions between seals and midwater trawl operations in the Australian Small Pelagic Fishery are common and can be lethal. The nature of interactions and effectiveness of a seal exclusion device (SED) in mitigating lethal interactions was assessed using underwater video. Recent fishing activity and the phase of the trawl operation significantly influenced interaction rates; interactions increased with the amount of recent trawl activity and were highest while the trawl was being set. Most seals accessed the trawl via the net entrance and exited via an escape opening located at the base of the SED. The size of the escape opening was the only operational factor that influenced mortality rates — simply enlarging the escape hole reduced lethal interactions by 79%. However, since all deceased seals dropped out of the net before they were brought on board, they would have gone unobserved without video monitoring. Limiting the concentration of fishing activity in space and time and refinement of the SED design, in particular to address dropouts, is recommended if mortality rates are to be reduced.

scholarly journals Does the closed fishing season influence the ichthyofauna consumed by Larus dominicanus?

2017 ◽  
Vol 65 (1) ◽  
pp. 9-18 ◽  
Author(s):  
Maiara Larissa Miotto ◽  
Barbara Maichak de Carvalho ◽  
Henry Louis Spach
Keyword(s):  
Bird Species ◽  
Strong Relationship ◽  
Morphometric Measurements ◽  
Fishing Activity ◽  
Trawl Fishery ◽  
Shrimp Trawl ◽  
Larus Dominicanus ◽  
The Family ◽  
The Mean ◽  
Closed Season

Abstract Fish that are incidentally caught by shrimp trawling represent a predictable and abundant resource for feeding several bird species, especially for the gull Larus dominicanus. This fishing activity is subject to disruptions throughout the year during closed fishing seasons, when other fishing modalities are exercised, which can alter the composition, abundance and size of the fish bycatch. This study evaluated the influence of the restriction of fishing period of shrimp (closed season) on the diet of L. dominicanus, on the Paraná State coast. From December 2013 to August 2014, 10 pellets were collected per month in two distinct areas that have shrimp trawl fishery as the main economic activity: one continental and another in an estuarine island. In total, 920 fish were identified, divided into four families and 15 species, especially the family Sciaenidae with 11 species. There were differences in abundance and biomass of species between areas and between seasons of pre-closure, closure and post-closure. Differences for the mean total length of the species were only detected between the pre-closed and closed seasons in one area. This study evidenced the strong relationship between L. dominicanus and the shrimp trawl fishery, the species composition identified in the pellets and their respective morphometric measurements follow the same pattern of the literature for fish discarded in trawling activities.

scholarly journals Short Communication: Population dynamics of double-spined rock lobster (Panulirus penicillatus Olivier, 1791) in Southern Coast of Yogyakarta

2018 ◽  
Vol 19 (1) ◽  
pp. 337-342
Author(s):  
RAKHMA FITRIA LARASATI ◽  
SUADI SUADI ◽  
EKO SETYOBUDI
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Short Communication ◽  
Mortality Rates ◽  
Southern Coast ◽  
Rock Lobster ◽  
Wild Stock ◽  
Fishing Activity ◽  
Males And Females ◽  
Asymptotic Point

Larasati RF, Suadi, Setyobudi E. 2018. Short Communication: Population dynamics of double-spined rock lobster (Panulirus penicillatus Olivier, 1791) in Southern Coast of Yogyakarta. Biodiversitas 19: 337-342. The southern coast of Yogyakarta, Indonesia, near to the Indian Ocean borders is a preferable habitat for lobster. Double-spined rock lobster (Panulirus penicillatus) is one of the prevalent species caught by fishermen. However the increased number of capture activities had an effect on the sustainability of global lobster fisheries. In order to sustain these fisheries resource, the preservation management of lobster should include wild stock assessments. Currently, the effect of fishing pressures on populations of P. penicillatus is limited. The objective of this research was to identify several factors affecting lobster population in terms of growth (carapace length (CL) and mass), recruitment, mortality rates, and exploitation rates in this species. Results showed that double-spined rock lobster had a longer size (CL) (45.2-55.1 mm) than that of females (55.2 mm-65.1 mm). While the growth rate (K) of males lobster is 0.85 year-¹ and its CL reached an asymptotic point at 125 mm (12 years old). Growth rate of females double-spined rock lobster was 0.55 year-¹ and its CL reached an asymptotic point at 125.5 mm (15 years old). The total estimation of mortality rates of double-spined rock lobster was 2.46, wherein 2.56 year-¹ for males and females, respectively. The estimated values of M were 1.08, 0.81 year-¹ for males and females, respectively while the respective values of F were 1.38 year-¹ and 1.75 year-¹ for males and females. The exploitation rate of males was 0.56 and females was 0.68. It has exceeded the optimal level (0.5) and reached overfishing value. Based on these results, it suggest that the time management of fishing activities such as by several approaches including the restricted time of fishing activity in spawning and recruitment season, the management of catching effort by the development of environment-friendly fishing gear, and the development of the lobster hatchery to reproduce and maintain their population naturally.

A hidden Markov model approach for determining vessel activity from vessel monitoring system data

2011 ◽  
Vol 68 (7) ◽  
pp. 1252-1264 ◽  
Author(s):  
David Peel ◽  
Norman M. Good
Keyword(s):  
Markov Models ◽  
Hidden Markov ◽  
Stock Assessment ◽  
Probabilistic Approach ◽  
Temporal Correlation ◽  
Fishing Activity ◽  
Spatial And Temporal Scales ◽  
Trawl Fishery ◽  
Eastern Australia ◽  
System Data

Many fisheries worldwide have adopted vessel monitoring systems (VMS) for compliance purposes. An added benefit of these systems is that they collect a large amount of data on vessel locations at very fine spatial and temporal scales. This data can provide a wealth of information for stock assessment, research, and management. However, since most VMS implementations record vessel location at set time intervals with no regard to vessel activity, some methodology is required to determine which data records correspond to fishing activity. This paper describes a probabilistic approach, based on hidden Markov models (HMMs), to determine vessel activity. A HMM provides a natural framework for the problem and, by definition, models the intrinsic temporal correlation of the data. The paper describes the general approach that was developed and presents an example of this approach applied to the Queensland trawl fishery off the coast of eastern Australia. Finally, a simulation experiment is presented that compares the misallocation rates of the HMM approach with other approaches.

Underwater Video Monitoring of Groupers and the Associated Hard-Bottom Reef Fish Assemblage of North Carolina

2012 ◽  
Vol 88 (1) ◽  
pp. 15-38 ◽  
Author(s):  
Erin J Burge ◽  
James D Atack ◽  
Craig Andrews ◽  
Benjamin M Binder ◽  
Zachery D Hart ◽  
...  
Keyword(s):  
North Carolina ◽  
Reef Fish ◽  
Fish Assemblage ◽  
Video Monitoring ◽  
Underwater Video ◽  
Reef Fish Assemblage

The utility of spatial model-based estimators of unobserved bycatch

2018 ◽  
Vol 76 (1) ◽  
pp. 255-267 ◽  
Author(s):  
Brian C Stock ◽  
Eric J Ward ◽  
James T Thorson ◽  
Jason E Jannot ◽  
Brice X Semmens
Keyword(s):  
Random Forests ◽  
Spatial Information ◽  
Generalized Additive Models ◽  
Estimation Method ◽  
Predictive Ability ◽  
Additive Models ◽  
Ratio Estimator ◽  
Fishing Activity ◽  
Trawl Fishery ◽  
Improved Model

Abstract Quantifying effects of fishing on non-targeted (bycatch) species is an important management and conservation issue. Bycatch estimates are typically calculated using data collected by on-board observers, but observer programmes are costly and therefore often only cover a small percentage of the fishery. The challenge is then to estimate bycatch for the unobserved fishing activity. The status quo for most fisheries is to assume the ratio of bycatch to effort is constant and multiply this ratio by the effort in the unobserved activity (ratio estimator). We used a dataset with 100% observer coverage, 35 440 hauls from the US west coast groundfish trawl fishery, to evaluate the ratio estimator against methods that utilize fine-scale spatial information: generalized additive models (GAMs) and random forests. Applied to 15 species representing a range of bycatch rates, including spatial locations improved model predictive ability, whereas including effort-associated covariates generally did not. Random forests performed best for all species (lower root mean square error), but were slightly biased (overpredicting total bycatch). Thus, the choice of bycatch estimation method involves a tradeoff between bias and precision, and which method is optimal may depend on the species bycatch rate and how the estimates are to be used.

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