Effects of commercial fishing regulations on stranding rates of bottlenose dolphin (Tursiops truncatus).

Fisheries management actions taken to protect one species can have unintended, and sometimes positive, consequences on other species. For example, regulatory measures to reduce fishing effort in the winter gillnet fishery for spiny dogfish (Squalus acanthias) off North Carolina (NC) also led to decreases in the number of bycaught bottlenose dolphins (Tursiops truncatus). This study found that a marked decrease in fishing effort for spiny dogfish in NC also corresponded with a marked decrease in winter stranding rates of bottlenose dolphins with entanglement lesions (P= 0.002). Furthermore, from 1997 through 2002, there was a significant positive correlation (r2 = 0.79; P= 0.0003) between seasonal bycatch estimates of bottlenose dolphins in gill nets and rates of stranded dolphins with entanglement lesions. With this information, stranding thresholds were developed that would enable the detection of those increases in bycatch in near real-time. This approach is valuable because updated bycatch estimates from observer data usually have a time-lag of two or more years. Threshold values could be used to detect increases in stranding rates, triggering managers immediately to direct observer effort to areas of potentially high bycatch or to institute mitigation measures. Thus, observer coverage and stranding investigations can be used in concert for more effective fishery management.

Die Lage der Fischbestände in Nordostatlantik, Nord- und Ostsee. Einschätzungen des Internationalen Rates für Meeresforschung im Frühjahr 2001

The spring session of ACFM gave advice for a number of stocks in the North Atlantic, North Sea and Baltic. The present assessment of the situation is given here for stocks of importance for the German fishery. These are: Blue Whiting: the stock size is rapidly decreasing due to high catches; ICES recommends a closure of the fishery. Herring (Atlanto-Scandian, Norwegian spring spawner): Stock is within save biological limits, weak recruitment of the recent years will lead to a further reduction of biomass. Herring (North Sea): revision of the assessment led to a different perception of the stock: SSB was in 2000 below Blim. Excellent recruitment will lead to an increase of SSB over Blim within this year, but ICES recommends to reduce fishing mortality on adults significantly. Herring (Baltic spring spawner in 22–24, IIIa): Still no increasing tendency is detectable. Herring (VIaNorth): stable. Redfish: generally further decreasing tendency observed, a reduction of the fishery is recommended. Signs of recovery visible only for two units. Greenland Halibut: State of the stock not quite clear, but slightly positive tendencies. The present fishing intensity should be reduced. Cod (Kattegat): Weak recruitment, outside safe biological limits. ICES recommends a closure of the fishery. Cod (22–24, Western Baltic): Stock situation unclear due to extensive migrations. F should be reduced by at least 10%.

Individual growth rates and movement of juvenile white shrimp (Litopenaeus setiferus) in a tidal marsh nursery

We measured growth and movements of individually marked free-ranging juvenile white shrimp (Litopenaeus setiferus) in tidal creek subsystems of the Duplin River, Sapelo Island, Georgia. Over a period of two years, 15,974 juvenile shrimp (40−80 mm TL) were marked internally with uniquely coded microwire tags and released in the shallow upper reaches of four salt marsh tidal creeks. Subsequent samples were taken every 3−6 days from channel segments arranged at 200-m intervals along transects extending from the upper to lower reach of each tidal creek. These collections included 201,384 juvenile shrimp, of which 184 were marked recaptures. Recaptured shrimp were at large an average of 3−4 weeks (range: 2−99 days) and were recovered a mean distance of <0.4 km from where they were initially marked. Mean residence times in the creek subsystems ranged from 15.2 to 25.5 days and were estimated from exponential decay functions describing the proportions of marked individuals recaptured with increasing days at large. Residence time was not significantly correlated with creek length (Pearson=−0.316, P=0.684 ), but there was suggestive evidence of positive associations with either intertidal (Pearson r=0.867, P=0.133) or subtidal (Pearson r=0.946, P=0.054) drainage area. Daily mean specific growth rates averaged 0.009 to 0.013 among creeks; mean absolute growth rates ranged from 0.56−0.84 mm/d, and were lower than those previously reported for juvenile penaeids in estuaries of the southeastern United States. Mean individual growth rates were not significantly different between years (t-test, P>0.30) but varied significantly during the season, tending to be greater in July than November. Growth rates were size-dependent, and temporal changes in size distributions rather than temporal variation in physical environmental factors may have accounted for seasonal differences in growth. Growth rates differed between creeks in 1999 (t-test, P<0.015), but not in 1998 (t-test, P>0.5). We suggest that spatial variation in landscape structure associated with access to intertidal resources may have accounted for this apparent interannual difference in growth response.