Eels at the Edge: Science, Status, and Conservation Concerns

2009 ◽  
Keyword(s):  
New Zealand ◽  
Management System ◽  
Stock Assessment ◽  
Catch Per Unit Effort ◽  
Commercial Catch ◽  
The North ◽  
Anguilla Australis ◽  
Unit Effort ◽  
Access Rights ◽  
Quota Management

<em>Abstract.</em>—The New Zealand eel fishery comprises two species, the shortfin eel <em>Anguilla australis </em>and the New Zealand longfin eel <em>A. dieffenbachii</em>. A third species, the speckled longfin eel <em>A. reinhardtii</em>, is present in small numbers in some areas. Major fisheries in New Zealand are managed under the Quota Management System. Individual transferable quotas are set as a proportion of an annual total allowable commercial catch. The Quota Management System was introduced into the South Island eel fishery on 1 October 2000 and the North Island fishery on 1 October 2004. Freshwater eels have particular significance for customary Maori. Management policies allow for customary take and the granting of commercial access rights on introduction into the Quota Management System. Eel catches have remained relatively constant since the early 1970s. The average annual catch from 1989–1990 to 2001–2002 (fishing year) was 1,313 mt. Catch per unit effort remained constant from 1983 to 1989 and reduced from 1990 to 1999. Statistically significant declines in catch per unit effort for New Zealand longfin eel were found in some areas over the latter period. For management, an annual stock-assessment process provides an update on stock status.

Impacts of spatial scales of fisheries and environmental data on catch per unit effort standardisation

2009 ◽  
Vol 60 (12) ◽  
pp. 1273 ◽  
Author(s):  
Siquan Tian ◽  
Yong Chen ◽  
Xinjun Chen ◽  
Liuxiong Xu ◽  
Xiaojie Dai
Keyword(s):  
Spatial Scale ◽  
Stock Assessment ◽  
Spatial Scales ◽  
Additive Models ◽  
Environmental Data ◽  
Catch Per Unit Effort ◽  
The North ◽  
Unit Effort ◽  
Data Collection And Analysis ◽  
North Western

Spatial scale is an important factor that needs to be considered in data collection and analysis in ecological studies. Studies focusing on the quantitative evaluation of impacts of spatial scales are, however, limited in fisheries. Using the Chinese squid-jigging fishery in the north-western Pacific Ocean as an example, we evaluated impacts of spatial scale used in grouping fisheries and environmental data on the standardisation of fisheries catch per unit effort (CPUE). We developed 18 scenarios of different spatial scales with a combination of three latitudinal levels (0.5°, 1° and 2°) and six longitudinal levels (0.5°, 1°, 2°, 3°, 4° and 5°) to aggregate the data. We then applied generalised additive models to analyse the 18 scenarios of data for the CPUE standardisation, and quantified differences among the scenarios. This study shows that longitudinal and latitudinal spatial scale and size of the spatial area for data aggregation can greatly influence the standardisation of CPUE. We recommend that similar studies be undertaken whenever possible to evaluate the roles of spatial scales and to identify the optimal spatial scale for data aggregations in the standardisation of CPUE and fisheries stock assessment.

scholarly journals Status of New Zealand fresh-water eel stocks and management initiatives

2007 ◽  
Vol 64 (7) ◽  
pp. 1379-1386 ◽  
Author(s):  
Don J. Jellyman
Keyword(s):  
New Zealand ◽  
Fresh Water ◽  
Management Strategies ◽  
Wetland Loss ◽  
Commercial Catch ◽  
Anguilla Australis ◽  
Generation Times ◽  
The Status ◽  
Quota Management ◽  
Average Size

Abstract Jellyman, D. J. 2007. Status of New Zealand fresh-water eel stocks and management initiatives. – ICES Journal of Marine Science, 64: 1379–1386. New Zealand has two main species of fresh-water eel, shortfin (Anguilla australis), which is shared with Southeast Australia, and the endemic longfin eel (A. dieffenbachii). Both species are subject to extensive commercial and customary fishing. The shortfin is the smaller and shorter lived, with typical generation times for females ranging from 15 to 30 years; generation times for longfin females are double this. The distribution and the abundance of both species have been compromised by habitat modifications, shortfins, the more lowland species, being affected by wetland loss, and longfins by weirs and dams. Although there are few concerns about the status of shortfins, there is increasing evidence of overexploitation of longfins, including reduced recruitment, reduction in catch rates, reduction in abundance and average size, and a regional reduction in the proportion of females. Eels are managed under the quota management system, although individual and regional quotas are set from catch histories because biological parameters are inadequate. Maori, New Zealand's indigenous people, have been allocated 20% of commercial quota, with additional quota set for customary take. The annual commercial catch of eels has halved over the past decade, and is now ∼700–800 t, shortfins comprising 66% of catches. Recent management developments have included enhancement of upstream waters with juvenile eels, consolidation of processing into fewer but larger units, setting aside of additional reserve areas to increase escapement of silver eels, increased management involvement of Maori, and development of regional management strategies.

A length-based Bayesian stock assessment model for the New Zealand abalone Haliotis iris

2003 ◽  
Vol 54 (5) ◽  
pp. 619 ◽  
Author(s):  
Paul A. Breen ◽  
Susan W. Kim ◽  
Neil L. Andrew
Keyword(s):  
New Zealand ◽  
Stock Assessment ◽  
Assessment Model ◽  
Data Sets ◽  
Catch Per Unit Effort ◽  
Commercial Catch ◽  
Data Set ◽  
Future Directions ◽  
Common Component ◽  
Joint Posterior Distribution

We describe a length-based Bayesian model for stock assessment of the New Zealand abalone Haliotis iris (paua). We fitted the model to five data sets: catch-per-unit-effort (CPUE) and a fishery-independent survey index, proportions-at-length from both commercial catch sampling and population surveys, and tag–recapture data. We estimated a common component of error and used iterative re-weighting of the data sets to balance the residuals, removing the arbitrary data set weightings used in previous assessments. Estimates at the mode of the joint posterior distribution were used to explore sensitivity of the results to model assumptions and input data; the assessment itself was based on marginal posterior distributions estimated from Markov chain–Monte Carlo simulation. Assessments are presented for two stocks in the south of New Zealand. One may be recovering after recent catch reductions; the other is over-exploited and likely to decline further. Assessment for the first stock was robust; assessment for the second stock was sensitive to the CPUE data and may be too optimistic. We discuss future directions and potential problems with this approach.

scholarly journals Development and evaluation of catch per unit effort indices for southern blue whiting (Micromesistius australis) on the Campbell Island Rise, New Zealand

2005 ◽  
Vol 62 (6) ◽  
pp. 1131-1138 ◽  
Author(s):  
Stuart M. Hanchet ◽  
Ron G. Blackwell ◽  
Alistair Dunn
Keyword(s):  
New Zealand ◽  
Stock Assessment ◽  
Independent Data ◽  
Catch Per Unit Effort ◽  
Age Composition ◽  
Commercial Catch ◽  
Fourfold Increase ◽  
Fishing Strategies ◽  
Acoustic Surveys ◽  
Campbell Island

Abstract This paper develops standardized commercial cpue indices for a highly aggregated spawning fishery in New Zealand waters, and verifies the indices using fishery-independent data. Indices were calculated for all vessels using three different measures of effort, and for vessel subsets based on processing type (surimi and dressed), and relative experience in the fishery. Trends in cpue were consistent with trends in fishery-independent acoustic surveys, age composition of the commercial catch, and recent stock assessment results. In particular, the cpue indices tracked the more than fourfold increase in abundance from 1993 to 1996 associated with the recruitment of the strong 1991 year class, and the decline in relative abundance as this year class was fished down. Despite this being a highly aggregated spawning fishery, there was little evidence for hyperstability. There were also significant differences in fishing strategies of the fleets between periods of high and low fish abundance.

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

2021 ◽  
Vol 322 ◽  
pp. 03006
Author(s):  
Naliyana Fitriya ◽  
Nahlah Alfiatuunisa ◽  
Suwarman Partsuwiryo ◽  
Eko Setyobudi
Keyword(s):  
Demersal Fish ◽  
Bottom Trawl ◽  
North Coast ◽  
Catch Per Unit Effort ◽  
The North ◽  
Central Java ◽  
Unit Effort ◽  
Trichiurus Lepturus ◽  
Trawl Fishing ◽  
Trawl Catches

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.

Stock Assessment and Life History of a Newly Discovered Alaska Surf Clam (Spisula polynyma) Resource in the Southeastern Bering Sea

1981 ◽  
Vol 38 (10) ◽  
pp. 1173-1181 ◽  
Author(s):  
Steven E. Hughes ◽  
Neil Bourne
Keyword(s):  
Bering Sea ◽  
Stock Assessment ◽  
Maximum Sustainable Yield ◽  
North Coast ◽  
Catch Per Unit Effort ◽  
Surf Clam ◽  
The North ◽  
Management Measures ◽  
History Of ◽  
Slow Growing

A 1977 exploratory survey of subtidal clam resources in the southeastern Bering Sea revealed extensive concentrations of Alaska surf clams (Spisula polynyma) along the north coast of the Alaska Peninsula. Using east coast hydraulic clam harvesters, subsequent 1977 and 1978 stock assessment surveys delineated a geographically isolated stock with an estimated exploitable biomass of 329 000 ± 52 000 t and conservatively calculated potential annual yield of 25 017 t (maximum sustainable yield) of whole clams. Production fishing trials at 13 sites in 1978 produced an average catch per unit effort of 815 kg/h with a 1.84-m-wide clam harvester.Life history studies indicated the species is long-lived (25 yr), slow growing (K = 0.135), fully recruited to the spawning population at 8 yr of age, subject to low natural mortality (conservatively calculated as M = 0.19), and attains maximum cohort biomass at ages between 9.4 and 13.0 yr. Biological rationale for management measures is presented.Key words: population assessment, sustained yield, surf clams, Alaska

Selecting a subset of the commercial catch data for estimating catch per unit effort series for ling (Molva molva L.)

2015 ◽  
Vol 165 ◽  
pp. 115-120
Author(s):  
Kristin Helle ◽  
Michael Pennington ◽  
Nils-Roar Hareide ◽  
Inge Fossen
Keyword(s):  
Catch Per Unit Effort ◽  
Commercial Catch ◽  
Catch Data ◽  
Unit Effort

Distribution and abundance of freshwater eels (Anguilla spp.) in Tasmania

1984 ◽  
Vol 35 (4) ◽  
pp. 463 ◽  
Author(s):  
RD Sloane
Keyword(s):  
New Zealand ◽  
Coastal Lagoons ◽  
Catch Per Unit Effort ◽  
Commercial Catch ◽  
North Eastern ◽  
Coastal Streams ◽  
Catch Statistics ◽  
The 1960S ◽  
Density And Biomass ◽  
Freshwater Eels

The distribution of A. australis australis Richardson and A. reinhardtii Steindachner in Tasmania was determined from electrofishing surveys and commercial catch records. A. a. australis is abundant in coastal streams and extends far inland in the major drainage systems to the main lakes in Tasmania's Central Highlands. Density and biomass estimates for A. a. australis in streams, <0.01-1 .40 m-2 and 0.04-23.01 g m-2, respectively, are similar to those recorded for A. australis schmidtii Phillipps in New Zealand and for A. anguilla L. in Europe, A. reinhardtii is restricted to coastal lagoons and the lower freshwater reaches and estuaries of streams in north-eastern Tasmania including Flinders Island. Substantial populations of A. reinhardtii reside in these areas (0.05 m-2, 114.66 g m-2 in Douglas River). Analysis of commercial catch statistics indicates that the initial eel yields from standing waterbodies were high in the 1960s by world standards, although landings and catch per unit effort have subsequently declined.

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