Neil L. Klaer

The Influence of Environmental Factors and Mitigation Measures on By-Catch Rates of Seabirds by Japanese Longline Fishing Vessels in the Australian Region

Summary: Most seabirds caught and killed by longline fishing are captured during line setting. Data collected by Australian observers on Japanese longline vessels from April 1992 to March 1995 were used to investigate the influence of various environmental factors and mitigation measures on seabird catch rates. Generalised linear models were used to test the significance of the effect of each factor. The environmental factor that most influenced the seabird catch rate was whether line setting was carried out at night or during the day. From the data examined, the chance of catching seabirds during day sets was five times greater than for night sets. For night sets, the chance of catching seabirds during the full half-phase of the moon was five times greater than during the new half-phase. The area and season fished were also significant, while wind, cloud and sea conditions were not. Considerable variation in the seabird by-catch rate among vessels was found. This was probably due to differences in their implementation of mitigation measures, as well as the clumped distribution of seabirds by area and time. Although the by-catch rate was significantly different among years, the differences were small in comparison to other factors. An examination of the influence of mitigation measures for sets made during the day in summer in the Tasmanian area showed that the level of bait thawing and unidentified factors related to individual vessels were most significant in determining the seabird by-catch rate, followed by the use of a bait throwing device. For this data set, the amount of cloud cover had an influence, while moon phase, sea conditions and wind strength did not. The effect of using bird scaring tori poles and lines was not examined, as these were used during all sets examined in detail.

By-catch of Albatrosses and other Seabirds by Japanese Longline Fishing Vessels in the Australian Fishing Zone from April 1992 to March 1995

Data collected by Australian observers, combined with logbook data supplied by all Japanese vessels fishing in the Australian Fishing Zone were used to estimate the total seabird catch and catch rates (and associated variances) within the Australian Fishing Zone by season and area. The species composition of sub-samples of captured seabirds was used in conjunction with the estimates of total by-catch to provide estimates of by-catch by species. The total by-catch of all seabird species by Japanese longline within Australian waters was estimated to be 2981 (coefficient of variation [cv] 17%) for the 1992 fishing year, 3590 (cv 15%) in 1993 and 2817 (ccv19%) in 1994. Because these estimates are based on birds observed hauled on board, they underestimate the total number of seabirds killed by fishing operations. The increase in total seabird by-catch between 1992 and 1993 is partly due to the use of monofilament nylon longline gear by two vessels in 1993, and the decrease from 1993 to 1994 was mainly due to a corresponding reduction in fishing effort. For the three years examined, 78% of the total seabird by-catch was albatrosses, with Black-browed Albatross Diomedea melanophrys and Shy Albatross D. cauta caught in the greatest numbers. Catches of Yellow-nosed Albatross (D. chlororhynchos), Wandering Albatross D. exulans and Grey-headed Albatross D. chrysostoma were also significant. The proportions of individual species caught showed considerable inter-annual variability.

Steam trawl catches from south-eastern Australia from 1918 to 1957: trends in catch rates and species composition

Haul-by-haul steam trawler catch and effort data for 1918–23, 1937–43 and 1952–57, which cover a large portion of the history of steam trawling in the Australian South East Fishery, were examined in detail for the first time. There were 64371 haul records in total. The catch-rate for all retained catch combined shows a strong decline overall, with a brief recovery during World War II, probably due to increased retention of previously discarded species. The fishing fleet moved to more distant fishing grounds and deeper waters as the catch-rate declined. The catch-rates of the main commercial species followed a similar pattern in a number of regions within the fishery. The catch-rate of the primary target species – tiger flathead (Neoplatycephalus richardsoni) – dropped considerably from the early, very high, catch-rates. Chinaman leatherjacket (Nelusetta ayraudi) and latchet (Pterygotrigla polyommata) – species that were apparently abundant in the early years of the fishery, virtually disappeared from catches in later years. The appearance of greater catches of jackass morwong (Nemadactylus macropterus), redfish (Centroberyx affinis) and shark/skate during the war and afterwards was probably due to increased retention of catches of these species. The disappearance of certain species from the catch may be due to high fishing pressure alone, or to a combination of fishing pressure, changes in the shelf habitat possibly caused by the trawl gear, and environmental fluctuations.

Abundance indices for main commercial fish species caught by trawl from the south-eastern Australian continental shelf from 1918 to 1957

Per-haul records of catches by steam trawlers on the south-eastern Australian continental shelf from 1918 to 1957 were examined for the main commercial species tiger flathead (Neoplatycephalus richardsoni), jackass morwong (Nemadactylus macropterus), redfish (Centroberyx affinis), latchet (Pterygotrigla polyommata) and chinaman leatherjacket (Nelusetta ayraudi). Catch rates in weight per haul per species were standardised to annual indices of abundance using a log-linear model. Standardised annual index trends for flathead, latchet and leatherjacket indicate a strong to severe decline during the period covered by the data. All species showed seasonal patterns, but the peak season varied depending on the species. The distribution of standardised catch rate by area also differed greatly by species, and no single area showed consistent differences across all species. Day trawls caught more flathead, redfish and latchet, while night trawls caught more morwong and leatherjacket. Moon phase had less influence on catch rates than other factors. The correlation of annual index trends to a number of annual mean environmental factors was examined and no strong correlations were found.

From data rich to data-limited harvest strategies—does more data mean better management?

From data rich to data-limited harvest strategies—does more data mean better management? Catherine M. Dichmont*, Elizabeth A. Fulton, Rebecca Gorton, Miriana Sporcic, L. Richard Little, André E. Punt, Natalie Dowling, Malcolm Haddon, Neil Klaer, and David C. Smith CSIRO Oceans and Atmosphere, Ecosciences Precinct, Dutton Park, QLD 4750, Australia Cathy Dichmont Consulting, 47 Pioneer Road, Redlands, QLD 4157, Australia Sheldon CSIRO Oceans and Atmosphere, Castray Esplanade, Hobart, TAS 7001, Australia School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, WA 98195, USA *Corresponding author: tel: þ61 7 3206 056; e-mail: cathydichmont@gmail.com

Fishery development and exploitation in South East Australia

Understanding the full extent of past ecological changes in human-influenced marine systems is needed to inform present management policies, but is often hampered by the scarcity of information about exploitation practices and population status over the entire history of fishing. The history of commercial fishing in South East Australia is relatively recent and thus easier to document. Our aim is to reconstruct such history and to use this information to understand general patterns and consequences of fishing exploitation. Intense exploitation of marine resources arrived in South East Australia with European colonization in the early 1800s, and unregulated sealing, whaling and oyster dredging resulted in the first documented significant impact on local marine populations. Exploitation extended to demersal resources in 1915 when the trawl fishery developed. Between the early 1800s and the 1980s, some of the exploited stocks collapsed, but fishing moved further offshore and in deeper waters as technology improved and new resources became available or were discovered. This phase of fisheries expansion masked the unsustainable nature of some fishing industries, such as trawling and whaling, and postponed the need for management regulations. From the 1990s onward, an increasing awareness of the depleted nature of some fisheries led to the establishment of management strategies aiming at a more sustainable exploitation of target stocks and, from the mid-2000s onwards, management strategies were revised and improved to better address the effect of fishing on multiple components of marine ecosystems. This led to the recovery of some depleted populations and to increased habitat protection. The relatively short history of fishing exploitation and the small scale of the fishing industry in South East Australia played a significant role in limiting the magnitude of fishing impacts on local populations and helped to achieve recoveries when fisheries restrictions were imposed. However, the experience in South East Australia also shows that ecological improvements for some depleted populations can be slow, suggesting that the time to recovery may be longer than expected despite relatively low historical and present levels of exploitation, favorable social conditions and a large investment in resource management and scientific research.