Nearly 1.6 million tagged herring (Clupea pallasi) were released in two separate programs (19361967 and 19791992) in British Columbia. Several thousand tags were released in each of 955 release sessions. Over 85% of the release sessions had subsequent recoveries. Almost 43 000 tags were recovered over all years. We re-assembled the tagging data into an electronic database, geo-referenced all tag release and recovery data, analysed spatial movements, and estimated straying and fidelity rates. The analyses do not wholly support the conclusions of previous work indicating high homing rates to local coastal areas. Estimates of fidelity, defined as the proportion of tags recovered in the same area as released, varied with the size of the geographic area used in the analyses. Fidelity rates are high for large areas, such as the Strait of Georgia (~10 000 km2), but lower for small geographical areas, such as inlets or bays (~100 km2). High fidelity is not necessarily evidence for "homing." Homing and fidelity are different biological processes and tagging cannot necessarily distinguish between them. Although fidelity rates for small areas are generally low, there are exceptions that may be evidence for the existence of biologically distinct populations in certain areas.
Pacific herring Clupea palhsi spawn in shallow and intertidal areas. Larval distributions and abundance of three major and several minor stocks were examined to determine if larvae mix among different spawning locations. The surveys were short, intensive, and occurred mainly within the first 30 days of larval life. Each major stock had a discrete larval distribution with continuous larval distributions within stock boundaries. Some overlap of distributions occurred among smaller stocks. Most larvae were found in inshore waters but there were no obvious oceanographic factors, such as fronts or eddies, to explain all the distributions. Estuarine circulation in inlets could promote larval retention in some areas. The results support the present geographic definitions for local herring stocks. The results are generally consistent with the concept of discrete larval distribution, including retention areas, as the basis for herring stock structure. Pscific &as Britiah Columbir Pacific Ocean FIG. I . The British Columbia coast with polygons showing the five major stock groups (QCI, PRD, CC, WCVI, GS) plus the locations of smaller Inlet stocks that were examined in the surveys. The Ahaded circles represent the locations of major spawning sites and the size of the circles is proportional to the cumulative spawn index from 1936-1966 (see Table 1 ) Thc numbers refer to the approximate positions of different herring sections ( Table 1).clusters of distinct spawning sites. As in other parts of the world, there has been an enduring interest about stock structure in Pacific herring (Tester, 1937(Tester, , 1949 Grant, 1981;Kobayashi, 1993). Some of the earliest surveys on Pacific herring larvae were used to comment on stock structure (Stevenson, 1962). This paper presents results of larval surveys conducted from 1985 to 1994 and relates larval distribution and abundance to the distribution and intensity of spawning. The larval distributions are examined relative to the present defined stocks and the prominent oceanographic features of each survey area. MATERIALS AND METHODSHERRING SPAWNING DATA-LOCATIONS AND MEAN DATES Data on the date, location and abundance of herring spawn have been collected throughout the British Columbia coast for more than 65 years (Table I ) (Hay & PACIFIC HERRING LARVAE 157 FIG. 2. General locations ofthe larval surveys, conducted from 1985 to 1994. Each station is indicated by a small cross. Names correspond to locations mentioned in the text. The surveys in the QCI and PRD rectangles were made in 1985-1986, GS surveys were made from 1989 to 1992 and inlets surveys were made in 1994. LH indicates locations of lighthouses.Kronlund, 1987). Eggkpawning data is collected for over 100 sections along the BC coast (Fig. I).SAMPLING VESSELS AND SAMPLING GEAR Larval samples were collected with 57-cm diameter (or 0.25-m2) bongo nets, weighted with 86 kg wt, hauled from 20-70 m research vessels, G. B. Reed, Vector, W. E. Rickrr or Culigus in deep-water locations and with smaller, 19-cm diameter (280-cm2) bongo n...
Hay, D. E., McCarter, P. B., Daniel, K. S., and Schweigert, J. F. 2009. Spatial diversity of Pacific herring (Clupea pallasi) spawning areas. – ICES Journal of Marine Science, 66: 1662–1666. Eastern Pacific herring spawn in intertidal and shallow subtidal areas. Spawning sites are conspicuous: milt turns coastal waters white, sometimes for distances of many kilometres. This attribute has enabled biologists to document spawning distributions for more than 70 years throughout the 29 500 km coastline of western Canada. Spawning distributions and spatial diversity have varied over time. When aggregated over 70 years (1938–2007), spawning occurred along 5574 km or ∼20% of the total coastline. Cumulative annual spawn length ranges from 131 (in 1966) to 770 km (in 1992). We examined annual changes in spawn distribution using spatial units of variable size, ranging in area from a maximum of >1000 km2 to a minimum of <0.1 km2. Assessment of spatial diversity varied with the size of the spatial unit. Spatial diversity estimated from small spatial units (area <0.1 km2) was significantly correlated with spawning-stock biomass (SSB). In contrast, there was no correlation, and sometimes opposite temporal trends, between SSB and all larger spatial units (mean area >0.3 km2). The choice of spatial scale can affect the results from analyses of other factors, such as SSB, that could affect spatial diversity of spawning areas.
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