Distribution of hoki (Macruronus novaezelandiae) eggs, larvae, and adults off Westland, New Zealand, and the design of an egg production survey to estimate hoki biomass

1998 ◽  
Vol 55 (7) ◽  
pp. 1682-1694 ◽  
Author(s):  
John R Zeldis ◽  
Rob C Murdoch ◽  
Patrick L Cordue ◽  
Mike J Page
Keyword(s):  
New Zealand ◽  
Egg Production ◽  
Abundance Estimate ◽  
Trawl Fishery ◽  
Spawning Aggregations ◽  
Biomass Estimate ◽  
Acoustic Surveys ◽  
Newly Hatched Larvae ◽  
Estimate Precision ◽  
Spawning Biomass

The winter spawning aggregations of hoki (Macruronus novaezelandiae) off the Westland coast, South Island, support New Zealand s largest trawl fishery. The distribution and abundance of hoki eggs, larvae, and adults from ichthyoplankton and acoustic surveys made during the period 1978-1993 were used to describe the location and timing of hoki spawning off Westland. Hoki spawned primarily in south Westland, around Hokitika Canyon, and south along the outer shelf and slope to Cook Canyon, although spawning biomass appeared to increase in north Westland later in the season. Older stage hoki larvae occurred shoreward of eggs and newly hatched larvae, suggesting onshore advection. The data were used to designate spatial and temporal egg sampling strata that significantly increased egg abundance estimate precision. The egg data were used to estimate annual egg production and, combined with data on fecundity and recruited proportion spawning, to estimate virgin biomass. The historical biomass estimate (1.48 million tonnes, CV = 29.4%) was probably biased down because the plankton tows were too shallow. It appears that a future egg production survey, using appropriate plankton sampling depths, could provide a biomass estimate of Westland spawning hoki sufficiently accurate and precise for management purposes.

Estimating the dynamics of spawning aggregations using biological and fisheries data

2016 ◽  
Vol 67 (3) ◽  
pp. 342 ◽  
Author(s):  
André E. Punt ◽  
David C. Smith ◽  
Malcolm Haddon ◽  
Sarah Russell ◽  
Geoffrey N. Tuck ◽  
...  
Keyword(s):  
Stock Assessment ◽  
Spawning Season ◽  
Turnover Rates ◽  
Spawning Grounds ◽  
Arrival Times ◽  
Spawning Aggregations ◽  
Average Proportion ◽  
Acoustic Surveys ◽  
Males And Females ◽  
Spawning Biomass

Acoustic surveys can provide accurate estimates of biomass at a particular location at a point in time, but provide a negatively biased estimate of the total spawning population unless the proportion of fish that are unavailable to the survey is accounted for. Changes to the ages and maturity stages of fish caught during the spawning season is evidence for turnover of fish during spawning and, along with information on relative abundance, provides a basis for estimating turnover rates. A model is therefore developed that tracks the numbers of males and females by age as they arrive on the spawning grounds, initiate spawning, complete spawning and leave the spawning grounds. This model can be used to determine the proportion of the spawning biomass on the spawning grounds over the spawning season. It is applied to data for blue grenadier, Macruronus novaezelandiae, off western Tasmania, Australia. The results can be used to estimate the average proportion of the population available to an acoustic survey, although this estimate is not likely to be very precise, owing to the high between-year variation in arrival times. However, the model provides a quantitative estimate of turnover rate that was previously not available, and is a rigorous basis for estimating turnover for stock assessment.

The Potential for Historical Studies of Fisheries in Australia and New Zealand

2001 ◽  
pp. 181-206 ◽  
Author(s):  
Malcolm Tull ◽  
Tom Polacheck
Keyword(s):  
New Zealand ◽  
Primary Sources ◽  
Commercial Fishing ◽  
Secondary Literature ◽  
Trawl Fishery ◽  
Small Family ◽  
The Impact

Malcolm Tull, Tom Polacheck, and Neil Klaer examine the primary sources - particularly printed statistical sources - and secondary literature in order to understand the impact of commercial fishing and harvesting of fish across Australia and New Zealand - including a case study of the multi-species Southeast Australain Trawl Fishery. The authors note that fisheries in Australia and New Zealand have historically been managed by small, family operations, so the records pertining to them are sparse. As a result, most of the records in this chapter come from governmental sources - such as reports and inquiries into Australasian fisheries.

Presence-Absence Sampling for Fisheries Management

1990 ◽  
Vol 47 (10) ◽  
pp. 1875-1887 ◽  
Author(s):  
Marc Mangel ◽  
Paul E. Smith
Keyword(s):  
Fisheries Management ◽  
Habitat Structure ◽  
Egg Production ◽  
Fish Stock ◽  
Search Process ◽  
Pelagic Species ◽  
Alternative Method ◽  
Probabilistic Description ◽  
Spawning Biomass

It is often important to estimate the abundance of a fish stock when the stock is somewhat depleted. For pelagic species this presents great operational difficulties, because adult surveys may be prohibitively expensive and time consuming. Here we introduce a method for estimating the spawning biomass of a stock by means of egg or larval surveys. In particular, we develop a series of models for presence-absence sampling of eggs or larvae and show how presence-absence data can be used to estimate adult spawning biomass. The models are based on an underlying probabilistic description of the aggregation of eggs or larvae, a search process, and a description of habitat structure. Methodologies are given for estimating the distribution of the size of the spawning biomass from presence-absence data. A case study of sardine is used to justify a number of the assumptions. The methods are applied to a 1985 survey for sardine eggs and are compared to an alternative method based on egg production.

Sperm whale abundance estimates from acoustic surveys of the Ionian Sea and Straits of Sicily in 2003

2007 ◽  
Vol 87 (1) ◽  
pp. 353-357 ◽  
Author(s):  
T. Lewis ◽  
D. Gillespie ◽  
C. Lacey ◽  
J. Matthews ◽  
M. Danbolt ◽  
...  
Keyword(s):  
Sperm Whale ◽  
Western Mediterranean ◽  
Small Sample ◽  
Line Transect ◽  
Ionian Sea ◽  
Sperm Whales ◽  
Detection Function ◽  
Abundance Estimate ◽  
Abundance Estimates ◽  
Acoustic Surveys

Acoustic surveys for sperm whales, using line-transect methodology, were carried out in the Ionian Sea and Straits of Sicily, Mediterranean Sea, in 2003. A total of 17 whales were detected along 3846 km of designed survey track in the Ionian Sea, and no whales along 892 km in the Straits of Sicily. This total was insufficient to estimate a detection function, so further data were obtained from quasi-random passages made elsewhere in the western Mediterranean in the same year. The encounters included several tight aggregations with inter-animal spacing less than 1 km, primarily from the western Mediterranean. Including individuals from these aggregations distorted the detection function due to the small sample sizes. No such aggregations were found during formal survey of the two areas of interest, and the aggregations were therefore excluded from detection function estimation. The resultant effective strip half-width was 10.0 km (n=40). On the assumption that g(0)=1, the resulting abundance estimates for the Ionian Sea were 62 (with 95% lognormal confidence limits of [24,165]), and 0 for the Straits of Sicily. The low abundance estimate for the Ionian Sea indicates that careful monitoring of the population is needed in the future. During passages along the Hellenic Trench, that were not part of the designed survey, several sperm whales including two aggregations were detected, suggesting that this may be a higher density area and ought to be considered as a separate stratum when designing future surveys.

In situ examination of the behaviour of fish in response to demersal trawl nets in an Australian trawl fishery

2004 ◽  
Vol 55 (8) ◽  
pp. 825 ◽  
Author(s):  
M. Piasente ◽  
I. A. Knuckey ◽  
S. Eayrs ◽  
P. E. McShane
Keyword(s):  
New Zealand ◽  
Escape Response ◽  
The Body ◽  
Trawl Fishery ◽  
Underwater Cameras ◽  
Swimming Mode ◽  
Towing Speed ◽  
Carangiform Swimming ◽  
In Situ Examination

In situ examination of the behaviour of fish was undertaken with underwater cameras positioned on demersal trawl gear used by Australia’s South East Trawl Fishery. Blue grenadier (Macruronus novaezelandiae), pink ling (Genypterus blacodes) and whiptails (Coelorinchus spp.) swam in an anguilliform mode whereas other species displayed a carangiform swimming mode. Tiger flathead (Neoplatycephalus richardsoni) and ocean perch (Heliocolenus spp.) were active in response to the approaching trawl net compared with the generally passive activity of whiptails, New Zealand dory (Cyttus novaezelandiae), and jackass morwong (Nemadactylus macropterus). However, when in the body of the trawl, gemfish were active while ocean perch, whiptails and New Zealand dory were generally passive. Some blue grenadier, ocean perch and whiptails escaped capture by passing through open meshes in the trawl mouth, whereas tiger flathead passed under the ground gear. In the trawl body, small numbers of blue grenadier passed through open meshes in the top panel whereas numerous spotted warehou swam faster than the towing speed, presumably escaping capture by swimming forwards and out of the trawl. Interspecific behavioural variation in escape response could be utilised to design more efficient trawl gears.

Use of the daily egg production method to estimate the stock size of Western Australian sardines (Sardinops sagax)

1996 ◽  
Vol 47 (6) ◽  
pp. 819 ◽  
Author(s):  
WJ Fletcher ◽  
NCH Lo ◽  
EA Hayes ◽  
RJ Tregonning ◽  
SJ Blight
Keyword(s):  
Western Australia ◽  
Egg Production ◽  
Production Method ◽  
Purse Seine ◽  
Batch Fecundity ◽  
Stock Size ◽  
Production Values ◽  
Sardinops Sagax ◽  
Western Australian ◽  
Spawning Biomass

The daily egg production method was used to estimate the spawning biomass of the sardine Sardinops sagax in the Albany region of Western Australia. Plankton surveys covering 10000 - 14000 km² were completed in July of 1991 and 1992 in three to five days using up to three boats. Adult sardines were obtained from the local purse-seine fleet. The spawning area was similar in both years at approximately 3800 km² (1100 nmile²), but the number of eggs collected was larger in 1991 with egg production values of 6.5 per 0.05 m2 day-1 compared with 3.9 per 0.05 m2 day-1 in 1992. The average batch fecundity values were similar (approximately 11000 eggs female-1) as were the proportions spawning (0.13 in 1991; 0.09 in 1992). The calculated biomass estimates were 23 121 t (CV = 0.51) and 16 121 t (CV = 0.44) in 1991 and 1992 respectively.

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